Building a Super Mod 2 cylinder Mariner/Yamaha

[Hounddog]

Because of the 70 CES Yamaha Thread several people are interested in building one of this power heads.

The Motor

In the states it was the Mariner 48, 55 and 60 hp, 2 cylinder, 15 inch, 1.84 or 1.71 gearcase, Yamaha made.
In Mexico and Canada it was the Enduro or Yamaha brand.
The motor was sold world wide as a commercial motor. Very sound and well build.
You can still get new parts thru Canada and Mexico.

Unlike the 70 hp Yamaha this motor has a solid steel crank, bolt on rods, twin carbs and a unique double exit exhaust system.

You can get Boyensen reeds for them.
You can use a 70 or 90 hp factory power trim on the long shaft version.
You can use Pro 50 power trim on the short shaft version
You can use the old in-line 4 and 6 cylinder Mercury power trim on either version

Stock Performance

We have only had one to try. It was a 55 hp Mariner long shaft. On a Delta and a VooDoo
high 50's with NO MODS at all.

What you should be able to get MOD

80 to 90 hp

Cylinder head MOD

There are one or two people on this site that can make small chamber heads for these. Being a commercial motor, the head is not a performance head. A performance head will make a big difference.

The Crank

Unlike the OMC 45 cubic inch crank which weakens after being reworked, this crank does not. It can be stroked to perfect spec and blue printed.

The Exhaust Chambers
I am sure someone will come up with some performance ideas for them.

Cost

Lots of low cost stuff out there, good bang for the buck.

[serious3]

as i've a twin 40 mariner/yammy i'll be watching this thread with interest!

[Hounddog]

It's a big chamber not a pipe

http://www.boats.net/parts/search/Merc2/Mariner/60%20%282%20CYL.%29/675-001171%20AND%20UP/DRIVESHAFT%20HOUSING/parts.html

[Hounddog]

http://www.boats.net/parts/search/Yamaha/Outboard/1994/C55ELRS/UPPER%20CASING/parts.html

NOTE: YAMAHA DID NOT MAKE THE 15 inch model to my knowledge.

[OUTBOARDER]

The 45ss 740cc twin easily will make 90hp on pump gas @ 7,000 rpm.
The cranks are good right from SEAWAY Marine. all we did was check for T.I.R. on mains, Cryo by "Three Hundred Below" and go. Turned 8,200 never a bottom end failure. Never re-used 20yr old bottom end parts, not for another driver. looked at a lot of
PWC twins to determine a canidate to reverse engineer. PWC engine builders will dyno all the way down to 3500 rpm which is a lot more meaningful than the other rec stuff out there.
In order to make a intelligent response regarding your engine would need to know more about it.

For the 45 did the following:

1- mod head
2- mod intake sys
3- Behind sleeve porting
4- mod water cooling
5- adapt PWC Chamber from Kawasaki 750 ZXI or Yamaha Super Jet 701
6- Light weight flex fly wheel

[Fast Fred]

they said "it hits like a piston port moda":eek::cool:

[Hounddog]

The 2 cylinder motor is the same bore and stroke as the 90 Yamaha. We know that with a little porting, reeds and head mods to get in the 170 psi range. That motor is getting 20 to 25% more power [110 to 115 hp] easy.

I would try the same in the 2 cylinder and go from there. Maybe try twin cow bell stainless exhaust tuners.

[Fast Fred]

Maybe try twin cow bell stainless exhaust tuners. that would be the Ticket.:cool:

[OUTBOARDER]

The 2 cylinder motor is the same bore and stroke as the 90 Yamaha. We know that with a little porting, reeds and head mods to get in the 170 psi range. That motor is getting 20 to 25% more power [110 to 115 hp] easy.

I would try the same in the 2 cylinder and go from there. Maybe try twin cow bell stainless exhaust tuners.

Talked to OMC Tech that developed 45ss tuner and learned that they tried over a dozen pipes. Two cylinder will NEVER do what Triple does from a tuner cause there is no cross plugging going on. Two into one chamber is a 20+ hp bolt on , why guess??

[Fast Fred]

the exhaust on the 60DES was separate from each other, twin cow bell. held all 750cc records.at about 5500rpms about 40hp slams into the power band. :cool:

[OUTBOARDER]

the exhaust on the 60DES was separate from each other, twin cow bell. held all 750cc records.at about 5500rpms about 40hp slams into the power band. :cool:
Yamaha SUPERJET 701 TWIN
comes stock with individual tuners similar to the 60 twin, makes 73 hp , with twin 38mm carbs and several other similarities to the 45.
Difference is in the late nineties RD Performance figured out a exhaust the worked from 3,500 rpms up. I was fortunate enough to talk to the engine guru there several times. He said they filled up a 40ft trailer with test pipes. They end result was a pipe that bumped a stock 73 hp Yamaha up to 100hp. In 1999 and 2,000 RD dominated every heat of the Worlds with that pipe. On a ported Yamaha they sell the pipe in a kit and gaurentee 140 hp from 7,400 to 7,800 along with arm wrenching acceleration. They said they could make more power but the drivers want acceleration. I have one of the pipes never used it or RD race porting specs. Just running rec specs. Stock Super Jet Exhaust opens at 89 deg ATDC Transfers open at 120/118 deg ATDC .

[88workcar]

Got one on hand, I'm all ears.

[OUTBOARDER]

Got one on hand, I'm all ears.
Are these engines Available?
How much for a beater to rebuild?
How many rpms will these turn w/o flying apart?
What is bore centers distance?
What is rod/ratio?
Can you take good pics of block inside and out?

[Hounddog]

Are these engines Available?
How much for a beater to rebuild?
How many rpms will these turn w/o flying apart?
What is bore centers distance?
What is rod/ratio?
Can you take good pics of block inside and out?

I can help you out a bit
2 cylinders. 46.4 displacement. The bore width is 3.23" and the stroke length is 2.83".
They will turn 8000
Solid steel crank
used complete motor $500.00
You can still get new parts thru Yamaha....same basic motor as their commercial 55 hp.
Wisco has pistons
Boyensen has reeds
Bone stock with no mods they turn 7000.

[sabine river killer]

that boy has a few of them from what he has told me

[OUTBOARDER]

I can help you out a bit
2 cylinders. 46.4 displacement. The bore width is 3.23" and the stroke length is 2.83".
They will turn 8000
Solid steel crank
used complete motor $500.00
You can still get new parts thru Yamaha....same basic motor as their commercial 55 hp.
Wisco has pistons
Boyensen has reeds
Bone stock with no mods they turn 7000.
Sounds good so far, how far apart are cylinders ?
Pull head lets look at it.

[88workcar]

Hounddog speak to me. What do I do?

[Hounddog]

Hounddog speak to me. What do I do?

I have a powerhead, it is up north in snow country, I can't get to it to take pictures to show.
I suggest you post the pictures of your motor and see what suggestions are made. I think the key is getting small chamber heads made [to get about 170 psi], port the motor like a mod 90 yamaha including finger ports. Add plastic reeds. Leave the exhaust as is until you get to try it. The exhaust mod would be the final tune.

[OUTBOARDER]

I have a powerhead, it is up north in snow country, I can't get to it to take pictures to show.
I suggest you post the pictures of your motor and see what suggestions are made. I think the key is getting small chamber heads made [to get about 170 psi], port the motor like a mod 90 yamaha including finger ports. Add plastic reeds. Leave the exhaust as is until you get to try it. The exhaust mod would be the final tune.

send me two blocks , will port behind liners , set up head for your fuel , make bolt on out the mid pipe(with removable beer can silencer) , mod intake system to engine set up . I keep one short block for my project. can get 100hp @7,000 with over rev to 7,800 on 93 pump gas with reliability and longevity.

[Hounddog]

send me two blocks , will port behind liners , set up head for your fuel , make bolt on out the mid pipe(with removable beer can silencer) , mod intake system to engine set up . I keep one short block for my project. can get 100hp @7,000 with over rev to 7,800 on 93 pump gas with reliability and longevity.

WOW!! 88 workcar....Take him up on that offer if you have 2 blocks. I would if I had two blocks!

[Fastjeff57]

Does anyone know what one of these twin Yamaha power heads weigh?

Jeff

[WalkWithMax]

Don, You may have to hook me up with one of these for next year! Or maybe I will still go with my '74 OMC 50 sizzler? My 50 has different pistons than the newer motors. The top ring is very close to the top of the piston. The motor is in great great shape, and I installed new rings, but I wonder if it will make decent power or not? Any thoughts on the older 44ci vs the newer 2cyl 50's and 60's?

[OUTBOARDER]

Don, You may have to hook me up with one of these for next year! Or maybe I will still go with my '74 OMC 50 sizzler? My 50 has different pistons than the newer motors. The top ring is very close to the top of the piston. The motor is in great great shape, and I installed new rings, but I wonder if it will make decent power or not? Any thoughts on the older 44ci vs the newer 2cyl 50's and 60's?

the pic of the white boat $500, 200lbs old pro did beat 2003 APBA short course nat and AOF nat winner from behind 3 heats at Camden NC oct 2003. There are a couple d mods out there that are faster than we were back then but not with punch out of turn. That power head blew 225 psi on the comp gauge! John Runne said the throttle was like a light switch
on or off.

[Mark75H]

To me when it came on the pipe it felt like suddenly being kicked by an elephant ... and that was before it was "right"

[Hounddog]

http://www.ebay.co.uk/itm/YAMAHA-MARINER-OUTBOARD-DRIVE-SHAFT-HOUSING-55-60H-P-2-STROKE-STD-SHAFT-/380394636025?pt=UK_CarsParts_Vehicles_BoatEquipmen t_Accessories_SM&hash=item58914982f9

DRIVE SHAFT HOUSING
FOR 55 / 60 H.P.
STD SHAFT ( SHORT)
LATE '70, 80 & 90
2 CYL ENGINES
ALSO FIT SOME MARINER 55 / 60 HP
NEW OLD STOCK

Yamaha part no : 687-45111-00

Mariner part no: 1587-7163M

[Hounddog]

http://www.ebay.co.uk/itm/yamaha-mariner-outboard-drive-shaft-housing-55-60h-p-2-stroke-std-shaft-/380394636025?pt=uk_carsparts_vehicles_boatequipmen t_accessories_sm&hash=item58914982f9

drive shaft housing
for 55 / 60 h.p.
Std shaft ( short)
late '70, 80 & 90
2 cyl engines
also fit some mariner 55 / 60 hp
new old stock

yamaha part no : 687-45111-00

mariner part no: 1587-7163m

That did not last long!

[Hounddog]

Is anyone got on to building one?
Here is a very nice stock one. Great platform for the mod!

http://www.ebay.co.uk/itm/YAMAHA-60hp-S-SHAFT-/120895080166?pt=UK_CarsParts_Vehicles_Boat_Engines _EngineParts_SM&hash=item1c25e886e6

[chris3298]

seen a lot of these motors around and had no idea there capable of so much power

[Hounddog]

Time to refresh this old thread. We should be able to get more first hand information with the resent replies on the T850 thread. Since 2012 this is what we have found out. Again this thread is all about the yamaha 60 D 2 cylinder model.
[1] I got a number of blocks. There is two different blocks for sure and maybe 3.
[2] there are at least 2 different heads. They even have different bolt patterns and gaskets.
[3] the last model of the 55 yamaha has a different block compared to the mid 80's mariner.
[4] Mark at Tuff boats tested a 55 hp yamaha on his Tuff 16 and got poor performance.

Question is: We know that these motors and the Nissan 2 cylinder model raced as a class in Japan on 12 foot tunnels and ran high 80 mph.
We now know that in 1988 a T boat with a 60 D Yamaha was running mid 70s mph. Why can't we get the same performance? What was different about those motors?

[Mark75H]

Question is: We know that these motors and the Nissan 2 cylinder model raced as a class in Japan on 12 foot tunnels and ran high 80 mph.
We now know that in 1988 a T boat with a 60 D Yamaha was running mid 70s mph. Why can't we get the same performance? What was different about those motors?

The boat and the prop

[Hounddog]

The boat and the prop

Mark YES that is part of it for sure. But, props are much better now than they were back then so the advantage has to be with us prop wise. Second in the case of the Japan tunnels. Those tunnels were no where close to being as well designed as the tunnels we tried. So the advantage has to be with the newer boats. Here is another bit of history. In the early 1990's Brad Collins Mirage Boats teamed up with Hydro Tec and did a boat and motor to race in that series. I don't think they got it competitive?? We have raced many Tohatsu's and Yamahas over the last 20 years. In the case of the 50 and 60 hp motors, we could never get the 2 cylinder models to perform as well as the 3 cylinder. Case in point is Formula 50. The top motor was the 50D Tohatsu and it did run in the 80 mph range. I have a lot of respect for the overseas race group. Maybe they can let us in on some secrets.

[25XS]

Here's a W60 Mariner in Iowa... (not mine)

https://waterloo.craigslist.org/bpo/5165025470.html

[hydrospeed77]

Hounddog,
any updates on this project? I'm interested in getting a 1977-1979ish Mariner 60 2cyl running well.

[Hounddog]

This project is an on going challenge and I still are NOT where I would like to be.
In brief here is an up-date.
- the motor I wanted to end up with is the original race version..model 6F1..it was only made one year. It had two stainless steel exhaust pipes similar to the single pipe on a 70CES...I have not seen them so I am not sure this is true.
- I purchased a new old stock 6F0 powerhead It was only made one year. It had a narrow exhaust pipe with an outer shell similar the the stock 70 Yamaha and not the large single piece system on the normal 48. 55 and 60 Yamaha.
- The motor had sat a long time and I could see a rust line on the cylinder walls so I removed the head to clean them up.
- Big surprise! This powerhead uses different gaskets...ends up there are several different blocks and they use different gaskets...took a year to get the gaskets.
- I followed the parts book picture to build an exhaust.
- I tried to use 90's ignition only to find the block bosses to attach the stator plate were in the wrong position.
- When I mounted the side cdi and coil assembly..the cowl did not fit.
- the driveshaft was 3/16's too long.
- I got what was to be an original lower unit from Finland only to find the drive shaft a smaller diameter and the gear case similar, it would not fit my mid section.
- then a find a YouTube video of a 6F1 motor pulling a tube....in sounds none racy and nothing special
I am taking a break from the project!

[Roflhat]

I can't believe that you would get near 3 cylinder (70ces) performance from a 2 cylinder. When you're tuning the 3 cylinders it's extremely effective because the cylinders are 120 degrees apart, hence why 3 cylinders and V6's are so popular.

[Hounddog]

I was not trying to get the 2 cylinder to outperform the 70CES. Initially I was looking for information on the mod 2 cylinder motors they raced in Japan. I could not find any. During the search I found the 6F1 motor which raced prior to the 70CES as a T850 and later as a T750 motor. Racers had many good things to say about them. We race T750 here and this motor is legal in stock form. That is why my focus switched to building a stock motor. The limited production and lack of common replacement parts such as gaskets was a surprise. I have not heard from anyone that still has a complete original 6F1 motor. So far they all have other powerheads which have replacement parts available.

[hydrospeed77]

I'd be interested to see if this 2Cyl outperforms a 3cyl 700cc 50hp. Both in stock form and just with basic mods like larger carbs, clean up the ports, mild exhaust tuner.

[Hounddog]

I'd be interested to see if this 2Cyl outperforms a 3cyl 700cc 50hp. Both in stock form and just with basic mods like larger carbs, clean up the ports, mild exhaust tuner.
I can answer that question. Based on our race experience here in T750. The 2 cylinder OMC motors outperform the 3 cylinder Tohatsu. APBA does not allow the 2 cylinder OMC to race in D class against the Mercury and Tohatsu for the same reason.

[hydrospeed77]

I can answer that question. Based on our race experience here in T750. The 2 cylinder OMC motors outperform the 3 cylinder Tohatsu. APBA does not allow the 2 cylinder OMC to race in D class against the Mercury and Tohatsu for the same reason.

I was not thinking OMC at all. Yamaha 2Cyl 55 / Mariner 60 vs. Yamaha 700cc 50. Of those two, what would run better in T750..?

[Hounddog]

Based on Thundercat and APBA Formula 50 racing the Tohatsu 50D is superior to the 50 hp Yamaha. We have not had a 50 Yamaha race in T750 here. The Tohatsu has the speed record in T750 at near 66 mph overseas. Based on our testing here we cannot get 60 mph with a Tohatsu. We had a stock 55 hp mariner/Yamaha run on a Delta. It ran in the 55 mph range same as the stock Tohatsu, so they would be close in top speed. I would give the edge to the 2 cylinder on the race course because it has more punch out of the corner.

[Hounddog]

Just to go off topic for a post. T750 class here is more of a drivers class and a weight class than it is a horsepower class. Racers can buy a used 750 motor here for under $1000. They can get a prop from Ron for $300. To $350. Put that on a T boat and it will run 50 to 55 mph depending on weight. The KEY to racing a T750 is never lifting off the throttle! It is a drivers class! WEiGHT! The closer you are to the 594 lb. minimum, the quicker you are. Our top T750 boats are running 60 to 62 mph on the course. As good as they are add 25 lbs in driver weight and the speed drops almost 2 mph.

[Xtoffer72]

https://www.facebook.com/kristoffer.fjelde/videos/t.741445925/442058520925/?type=2&theater

Norwegian built S-850 old UIM formula4, boat and engine built in Norway

[Fastjeff57]

What's a typical T750 motor?

Jeff

[Maasters]

I have a 1980 60E shortshaft 150psi in both cyl. Hear6170961710

[gbooysen]

HI all

I have a 55BE which still has the shocks on the outside of the mount. I'm looking for info to possibly upgrade this to power trim.
Here in South Africa the spares for these are very limited and I'm battling to find info here.
Can this be done? how feasible is it and what do I need? Neck, mount and the trim unit?

Thanks
Gerhard

[Fast Fred]

i think a Yama pro50 t&t bracket will fit that

[Hounddog]

i think a Yama pro50 t&t bracket will fit that

You have some options:
- the old style twin ram Mercury fits
- as Fred mention.. the Pro 50 can be modified to fit You switch the lower yoke on the steering arm and make the two top bolt hole a bit larger
One problem with these old outboards is taking them apart without breaking parts and it takes more time than you think.
So the best option maybe to get an aftermarket add on trim system like a CMC.

If by chance this is a long shaft model..any 70 hp Yamaha long shaft model power trim bolts right on.

[gbooysen]

You have some options:
- the old style twin ram Mercury fits
- as Fred mention.. the Pro 50 can be modified to fit You switch the lower yoke on the steering arm and make the two top bolt hole a bit larger
One problem with these old outboards is taking them apart without breaking parts and it takes more time than you think.
So the best option maybe to get an aftermarket add on trim system like a CMC.

If by chance this is a long shaft model..any 70 hp Yamaha long shaft model power trim bolts right on.

Thanks Guys

Yes this is the long shaft version, so I'm now keen on the 70hp suggestion - not sure where it will fit in as this bracket seems quite full or are the 70's also on the outside? sorry for all the questions, I just have to weigh my options here and getting info is key....

thanks again

[Hounddog]

You replace the complete clamp bracket assembly. The 55 hp mid is almost exactly the same as the 90 Yamaha. So you can use 70, 90 or late model 55 Yamaha. The problem is taking the old parts off your motor.

[Maasters]

Hounddog I have 2 complete mariner 60hp longshafts. One is a 675 and one is a 6F0

[Hounddog]

I did reply to your private messages. The two motors you have are different and I am surprised you got 6F0 parts and gaskets easily. Good for you. The exhausts are different. One is the single piece and the other 6F0 has a pipe and outer shell.
The 6FO has different Pistons. The other one is much more common and similar to the newer Yamaha 55 parts.

[Supremesoundzuk]

69044Hi there all just come across this forum and this post so thought I’d sign up I’m currently having a 60de 6f1 rebuilt and advise on mods would be much appreciated :)

[Hounddog]

69044Hi there all just come across this forum and this post so thought I’d sign up I’m currently having a 60de 6f1 rebuilt and advise on mods would be much appreciated :)
IF? Yours is an original 60de you already have the best model. Your motor has all the good parts. Please post pictures and port measurements. We have never seen the inside of an 6f1 powerhead. Thanks for posting.

[Supremesoundzuk]

I beleive so yes :) it’s currently being completely stripped leg and bracket bead blasted and any repairs and painted, power heads stripped and being chemically dipped ready for a full rebuild

The plan is some mild port work and head work and have the crank rods and flywheel balanced we don’t have any rules on mods,

If anyone has any suggestions feel free to comment :)

[Supremesoundzuk]

Bracket pic

69045

[Hounddog]

Here's is what WE know about the twin Yamahas.
- in the late 1970's to early 1980's Yamaha made the displacement larger
- the block was the 6F0 ....60C Yamaha....60E Mariner
- it was still 60 hp at the crank same as the smaller displacement version.
- the 60D with the 6F1 block was produced in 1981-2
- the 60D had the special tuner, maybe larger carbs, porting change?, head change? piston change?
We have never seen a 6F1 block disassembled so that information would be good to know.
- Yamaha when BACK to the smaller displacement block after 1983 and the motor uses the same sleeve,
rod and piston as the 90 hp 3 cylinder models.
- parts for the 6F0 powerhead are hard to find...the 6F1 must be harder to find.
- we know it is very easy to get 120 plus hp out of the 90 hp yamaha.
- the difference between the 90 and the twin is the cylinder head dome.
- a twin with the same style head SHOULD be 2/3 the hp of the 90 hp.
-with the same mods as the 90, the small displacement twin should make over 75 hp
- the 6F1 was said to produce approximately 65 hp

[Supremesoundzuk]

I can’t get some measurements il ask my guy

Mine is yes fitted with a trumpet style tuner al be it relitively battered
69047
I’ve had some 3D printed velocity stacks
69046

The part number on my carbs is 66323 which is a little confusing but the air jet is larger than any listed at 180 I don’t know what the main jets are it’s not that far apart yet

[hydrospeed77]

After asking around and searching for info, I have a feeling that the 6F1 was unique in that the displacement was exactly 750cc - It had slightly smaller bore pistons than the very common 760cc 82mm bore engines. I can't fully confirm that but I have a strong feeling that was the case based on part numbers and measurements of pistons.

The 6F0 has 84mm pistons for 798cc.

My guess is that all of them share the same crank and are 72mm stroke.

I noticed in some photos, the 663 Cyl Head is different from the common 675 Cyl Head, and looks like the 663 Air Box is smaller than the late 70s' Mariner 60 and mid-90s' Yamaha 55.

I've now seen photos of 3 different flywheel designs. 4 if you count the 6F0, which has different Flywheel, Stator, CDI than the most common newer Yamaha 55hp and older Mariner 60hp.

[Hounddog]

full rebuild

How have you made out with the rebuild? Were you able to find new parts and gaskets for the motor? Were you able to confirm that the motor is 750 cc?

[Supremesoundzuk]

So far it’s now fully stripped, James my builder is pretty sore it’s mever been apart paint was still good over all the parts, the power head parts are in the chemical tank being stripped
the mid section and all bracket parts tray etc have now all been bead blasted ready for a oem looking rear exhaust exit
Crank has had all the bearing fits cleaned up ready to be balanced
Fly wheel is next to have some lightening and also be balanced
Gearbox is stripped of paint ready for a bobs ow water pickup and extended skeg
Block head and reed block is off to bdk for cnc liner porting then port matched and some head work

Ccm reeds all new bearings and gaskets and starter have arrived

[fs5]

Nice!

[Supremesoundzuk]

Few more updates

My engine builder is very busy at the moment but hoping to get on it soon

All the right bearings and gaskets have now arrived this was a mission
The ccm reeds have arrived along with the bobs nose cone from the states
New starter fuel pump and coils have arrived


Powerhead is back in the chemical tank for the final time it’s been in cleaned and in many times to strip back completely

Flywheel is having a little bit of a tweek removing the pull start, then the crank road pistons and rods are off to be balanced before being loosely assembled so it can go for cnc porting and head work.

While that’s happening hoping to have the one come fitted and a glare gearcase mods some tweeks to the leg, solid mounts assembled, fresh paint ready for the powerhead

[88workcar]

send me your number, 985-519-0367

[Supremesoundzuk]

Lwp nosecone underway

[Hounddog]

Lwp nosecone underway
Did you ever get the motor complete and running?

[Supremesoundzuk]

71208
Did you ever get the motor complete and running?

The build is still under way my guy is back on it next week

[Hounddog]

71208

The build is still under way my guy is back on it next week

Any updates?

[Supremesoundzuk]

75363Things went very slow I’ve picked up the parts and am continuing myself.....

[Supremesoundzuk]

75364But here is how it’s going

[Supremesoundzuk]

Few more updates, carbs are clean and together 75365

[Supremesoundzuk]

Old exhaust reliefs welded 75366

[Supremesoundzuk]

75367

All cleaned up all welds ground back nose cone faired, lots of fettling done to the castings,

Hoping to get all the power head parts which have also been very played with away to be cerakoted This weekend

[Supremesoundzuk]

Cylinder head sneak peek o ring and modified combustion chamber for a better burn 75368

[Supremesoundzuk]

Yam 40 hp bracket which I will be using with a custom jack plate I’m working on 7536975370

[Supremesoundzuk]

Powerhead parts ready for coating 75371

[hydrospeed77]

After asking around and searching for info, I have a feeling that the 6F1 was unique in that the displacement was exactly 750cc - It had slightly smaller bore pistons than the very common 760cc 82mm bore engines. I can't fully confirm that but I have a strong feeling that was the case based on part numbers and measurements of pistons.

The 6F0 has 84mm pistons for 798cc.

My guess is that all of them share the same crank and are 72mm stroke.

I noticed in some photos, the 663 Cyl Head is different from the common 675 Cyl Head, and looks like the 663 Air Box is smaller than the late 70s' Mariner 60 and mid-90s' Yamaha 55.

I've now seen photos of 3 different flywheel designs. 4 if you count the 6F0, which has different Flywheel, Stator, CDI than the most common newer Yamaha 55hp and older Mariner 60hp.

I had a great person help out and measure a new old stock 6F1 piston, and as per speculation, the 60DES bores were 81.30mm for a displacement closer to 747 or 750cc..
Stroke and rods are the same as the 3cyl 85/90, but ports are slightly different. 55B is also slightly different from the 85/90hp. Not sure yet on the 55B/60DES port differences - might be none.

[hydrospeed77]

I recently re-read this whole thread and want to clarify a few things I've found more recently.

There are claims in this thread the 6F1/60DES tuner was dual horn - it is not - you can find pics online and in the most recent posts here of a single opening tuner. Both cyls feed in to the one pipe tuner at the adapter plate.

Some folks are thinking that the 55B is a 2cyl version of the 85/90hp. They are very close but they are not the same. Sleeve port map is different, but close. Combustion chamber shape and volume is different. Carbs on the 2cyl are different in terms of venturi size and overall design. What is the same and even use the same part numbers are the rods and pistons (and bearings) - both the 90hp and the 55B use the same pistons and rods. I believe all these 2cyls use the same rods. 6F0 had 84mm bores, 6F1 had 81.30mm bores. 90hp and related 3cyls,and the 55B have 82.00mm bores.

[Supremesoundzuk]

Indeed my tuner is a steel construction with a single cone I’ve recently had it repaired and ceramic coated

There is also much confusion as to the ratio of the gearbox
The 55b was 1.85 13t 24t
The 60de 6f1 is 2.0 13t 26t

Bores as your stated the 6f1 is smaller

My motor parts are now back from being cerakoted happy with the natural looking finish wanted them to loom retro just out the cast look 75586

[Supremesoundzuk]

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[hydrospeed77]

To clarify and correct for historical purposes, the 60D (6F1) came with 1.85 gears from the factory (13:24). I'm guessing some racers lobbied to have the 13:26 gears from the 2cyl 40hp (679) officially homologated in via supplemental homologation.

update:
I have older Yamaha docs saying 60D came with "675" gears, like the 70CES (1.71), and a Yamaha pamphlet from like 1984 or 1985 stating 1.85 gears for the 60DE.
So either a change at some point or one of them is incorrect.

[Supremesoundzuk]

To clarify and correct for historical purposes, the 60D (6F1) came with 1.85 gears from the factory (13:24). I'm guessing some racers lobbied to have the 13:26 gears from the 2cyl 40hp (679) officially homologated in via supplemental homologation.


No the 6f1 was homoglated with 13t 26t

[Supremesoundzuk]

Bit more progress

Dry fit of the parts to see what it would look like

Still fettling away at the gearbox making the nose cone look a little more oem, tweeked the water definition plate to blend into the cone and tweeked the anti ventilation plate a little just straightened it up and blended it in lost a little bit of material off each side

[Dvdracing]

Not a super mod but she run 74mph, mariner 30hp 689 model75644

[Supremesoundzuk]

Latest updates

[hydrospeed77]

No the 6f1 was homoglated with 13t 26t

Yes, but only at a later date. It never came with 2:1 gears from the factory. The RYA homologation that includes the 2:1 gears clearly states those gears are from the 40F "679" model, and in fact shows the "675" part number as the factory gears (same part number as the 70CES 6J2 factory gears).

[Supremesoundzuk]

Yes, but only at a later date. It never came with 2:1 gears from the factory. The RYA homologation that includes the 2:1 gears clearly states those gears are from the 40F "679" model, and in fact shows the "675" part number as the factory gears (same part number as the 70CES 6J2 factory gears).

Yes indeed it does show the forward and reverse gears being replaced with 26t Which is how it was inspected for racing
the pinion was always 13t though so originally is was 1.85 then changed to 2.1
the ces was 14t 24t making 1.71 was it not

[hydrospeed77]

Yes indeed it does show the forward and reverse gears being replaced with 26t Which is how it was inspected for racing
the pinion was always 13t though so originally is was 1.85 then changed to 2.1
the ces was 14t 24t making 1.71 was it not

All the 60hp models from around 1980/1981 came with the 1.71 "675" gears. 60A "675" and 60C "6F0" (the two I own, all original) as well as the 60D "6F1".

Racers probably saw that due to the power output and props available, they wanted more appropriate gear ratios and started using the 55B and 40F gears, and requested to have those gears homologated. So in the end you can run factory gears, or whatever the rules allowed/homologated.

The only place I see the 60D showing 1.85 ratio is on race brochure where it is listed side by side with the 70CES in the same document. So at minimum 1984. I'm guessing it is either a typo or Yamaha changed the included gears based on recommendations from racers. Yamaha likely saw that the 1.71 gears worked well on the 70CES, and since it made more power than the 60D, changed the 60D factory gears so that props can be shared between the two motors (if you are running both classes, for example). 60D product development was highly influenced by racers in the UK back in the early 80's.

[hydrospeed77]

Here are some pics from assembling a short shaft from a long shaft. This was a few years ago. I'm adhering to our "Super Stock" racing rules. Basically the powerhead has to be stock, and/or built to a specific spec. We use UIM/RYA/APBA homologation mostly, but limit cranking cyl pressure to 160psi. The other allowances are fibre reeds, exhaust tuner is open to modding, and we can add power trim, adjust jetting and timing. No porting other than casting cleanup, no low water pickups or nose cones. I've since rebuilt my powerhead with oversize pistons and a bit more chopped off the exhaust, but no cyl head shaving yet, so still at like factory compression 140psi. The block in this photo is from a 1979 Mariner 60hp "675" model, the cyl head is blue - from a Yamaha 1989 55hp, but stamped "675" just like the older 60hp Mariner. I've also since installed the more modern flywheel which is also about 50g or 80g lighter I think.

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The guys and gals in my class running OMC have the SST45 APBA specs as their limits - they are revving fairly easily over 7000rpm. My "55hp" Yamaha does not rev easily past 6500. Well, that entirely depends on how it is propped. But the OMC folks have a small power advantage - I have to gain 2mph or maybe like 300rpm running my current prop and gears if I want to catch the fastest OMC boats.

[Supremesoundzuk]

Bit more progress it’s all coming together

Combined jackplate/mount coming along nicely, all the bits are now cerakoted,
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[Supremesoundzuk]

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[Supremesoundzuk]

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[Roflhat]

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[Supremesoundzuk]

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[Trnissen]

The engine is quite impressive :cool: - have a couple of 6f0´s myself and i would be very interested in getting some info on headwork and light porting. I have one very original that i want to keep that so, and a second one for modifying - getting short leg fun outboards is quite a challenge - :-). Did you get high performance reed valves? - and do you run the standard carbs?779047790577906

[Supremesoundzuk]

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