Mild hop-up of a Merc 350 . . .

[smittythewelder]

Anybody here ever race the old 30" two-cylinder Merc? I saw a couple of the four-cylinder 650 version in the F classes, but only one full-race 350 with megaphones for COH. I think a couple of guys ran 350s in C Service when the rules were opened up in the Seventies. Right now I'm Googling to see if I can find anything on the stock motor, how long a model run it had, lower unit ratio, etc..

Anyway, a guy is wondering about getting some more snort out of a 350 for a playboat, gas-and-oil, no stacks. I would imagine he could carve a little more exhaust timing into the ports and install a slightly larger carb. Does anyone here have a guess what he could look for as to rpm power-peak (so we can make a rough estimate of appropriate propeller pitch)? Before he starts grinding, we want to make a wild guess about the prop pitch so I can ask Ron if such a prop can be found. Of course the guy wants a guess of horsepower, too.

[Hounddog]

There is not a lot to work with because of the design of that motor. A better choice in my view of a similar size motor would be the yamaha/mariner 40 hp 2 cylinder.
I don't know if anyone has tried to mod one of these, but it appears to be a much better design.
https://www.thehulltruth.com/attachment.php?attachmentid=10739&stc=1&d=0

[Bill Van Steenwyk]

Smitty:

Get hold of Chris Hellsten. He can accept PM's on Hydroracer. May be registered here also but have not seen his name. His Dad, Pete, owned one of these back in the day that won the APBA Nationals several times, once with him (Pete) driving I think, and another with his Daughter Kristi. If Chris was aware of the mods that were done and remembers, he may be able to help you. I doubt there were very many mods allowed as the Speeditwin guys were at war with the ones trying to use the Merc and probably would not have allowed many if any as there were several of them on the PRO Commission at the time.

[Fastjeff57]

Seeing that's merely an enlarged Super Hurricane, there are lots of mods you can do and they will make a difference. I modified one with external reeds and dual carbs years ago that was a runner.

In the photos I used a Merc 25 tower initially (with a driveshaft adapter), but props were not available. I then used a Mark 55 tower. Still very light, even with the E starter.

Jeff

[smittythewelder]

Thanks, fellas. Hounddog, you may well be right, but the idea is to use an old, cheaply-acquired motor and not carve-up (and maybe screw-up) a perfectly good pleasure boat engine just for occasional use on a little lake-racer/playboat. Thanks for the tip Bill, and I do remember the controversy that attended the addition of Mercs to C Service. I have one of the Y80s lightly boosted, not to Restricted B levels but more zippy than a stocker, and have hinted to the guy that something light and compact and with a racing lower unit and good prop would give him a lot better powerplant. Jeff, that's a neat piece of work, and I'll point the guy to your photos. But you say you couldn't find a good prop without using a Quickie. That's an issue we'd have to figure out before he tears the engine down and starts making chips.

And just to add confusion, he's now started talking about a 35hp Johnson from the Sixties, so who knows, LOL.

[rumleyfips]

I think there is a CService Mercury in Mark Suter's collection. I'll liik later.

[rumleyfips]

Quincy Looper Racing site, Mark Suter collection page first and second pictures from the bottom . Bonus just for you, it has an Anzani flywheel.

[rumleyfips]

Here's one running pretty well out front. Took me a while to find it .
http://hydroracer.net/forums/forum/main/general-hydroplane-runabout-discussion/18921-b-1-bomber-class-start-n-up-aof/page2

[rumleyfips]

Lots of pictures over a few pages,
http://www.boatracingfacts.com/forums/showthread.php?7707-quot-Name-That-Outboard-quot/page23

[bobvdinghyracer]

couple pics of a 35hp twin on a mk20 leg used mk30 pan cut down for adapter only mod was a drivshaft adapter ... easy to do this would also work for a ke/kf/ kg leg and a ab quickie ... as far as props not hard to adapt just about anything you can come up with the motor pictured was built for a buddy using a merc 13 pitch bronze stock prop , i also have 1 on a cut down mk20 leg with a kg gearbox at bottom 16/21 gotta find pics of it

6486464865

[bobvdinghyracer]

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[bobvdinghyracer]

pics above showing in my hand is what i use for adapters readily avaible apx 10 bucks machine to fit your prop , a pic og 35 twin on a short mk 20 leg with custom built kgfoot highly modded other pic is cut down mk30 pan , shaft adapter using an old 20cube crank bottom and a upper part of a 4 cyl drv shaft mated together the other 2 pieces were needed dor the newer twin with more cubes and newer rear bolt pattern not needed for early 35.... this ran high 40`s on a hard bottom zodiac dinghy , this yr gonna throw it on my halkelly fooling to see what she can really do .... lake racer ... this all can be built pretty cheaply , fun and fast btw the prior 1 i built above, all pretty is fully dressed with stock 35 hp cowlings and merc 200 decals ha ha runs sweet and weighs apx 85-90 lbs (full gearshift)

[smittythewelder]

WOW, what a response!! Rumley, Dinghy Bob, thanks so much, what fun projects!! Shows you really can "make a silk purse from a sow's ear" sometimes. I have to study those photos, there's a lot to see there. Thanks again!

[bobvdinghyracer]

forgot to mention , yes she will take some exhaust porting with a smile ... and ya i did ... even better is the newer version ... little heavier .. more cubes apx 33 cube and the newer style pistons , some porting use the power ported pistons from a triple ... litle more grinding on the ports and .... , if your daring build some reed blocks and add 2 carbs instead of 1 .... should be interesting ... i did 1 but was stock on the mk 20 leg stock g box stock height .... had a lot of balls ... thats what those other plates were for in above pics ... the boat i had at time didnt handle well and project was shelved for the time but am gonna do another with above mods .... why ? cause i can .... picture the 650/700 x race motor merc built and could be same idea just 1 less cyl. should make some serious power for an old anchor ... and CHEAP FUN

[OldRJexSea]

Smitty, I took a look at your Tech post as you suggested. I suppose that folks enjoying themselves by hot rodding those old motors in modern times is a good enough outlet for desires to apply their creative energies in assembling usable gear at modest cost.

I am ambivalent about such efforts mostly because I am too bleeping old which is compounded by no lifetime left to build a truly modern outboard racing motor. A small class size 2-stroke using external intake pumping, hydrodynamic bearings, (or recirculating oil mist for mod. roller bearing motors), and electronic FI & ignition; all the proper items needed to have a motor which minimizes the current pollution of air & water by outboard motors and is much more efficient at producing power. (And running on standard pump E85 ethanol (or E96) for even less pollution). (As you know, my last effort on a standard 2-stroke design was 1972, no time then either).

I remain truly curious as to why major motorcycle manufacturers developed such a fine set of 2-stroke machines until the 1990’s but did not change to the above mechanical methods when the EPA set exhaust emissions standards that could not be met with lubricating oil included in motor fuel.

The Moto-GP racing which eventually set 4-stroke displacement at almost twice the allowed 2-stroke motor size was probably tied partly to certain motorcycle manufacturers wanting into the game using their newer 4-stroke high performance Street motors plus the looming emission standards in the major markets. The GP racing drove prestige & sales for the major manufactures so they took the costly path of total redesign to 4-stroke for their machines after the GP dominance of 2-strokes was ended by the size limitations. Much easier to add systems than total redesign but maybe not given Accounting Dept. projections.

Bottom line, in my estimation, for folks with a bunch of energy left to fiddle with old 2-stroke outboards would be to develop and add the systems listed above to prove that truly clean, efficient, high power density, 2-stroke motors requires a different mindset but is worth the effort.
Somebody can do it !! Might be more fun too.

RR

[Fastjeff57]

Dingy Bob made me the driveshaft adapter used with the dual carb, external reeds motor on page one. He does nice work!

Jeff