75 short shaft hustler build ( beginner please help! )

[camohunter]

I'm Building an OMC 75 Short Shaft Hustler/Stinger. I've taken a lot of notes from this site, but still need advice on what I should do. This motor will be a river motor and probably be used on one of the new Fancy aluminum speedy duck boats coming out of Arkansas. I would like to do some light-medium mods, but keep the motor dependable.

I have the following parts:

- Getting a 1969 55hp 3 cylinder Evinrude center section with a 1978 75hp tuner

- An 81' model 49er fishing motor

- An 80' Stinger with club foot

- A 30" tiller handle off of a V4 evinrude



Questions:

What are the advantages of the 56er over the 49er?

Will the 49 crank fit a 56 block? (I know some of the later 56ers have a diff spline)

Will the top-end speeds be much different between the two?

Should I build a 49er since I already have the blocks on hand?

Will the 56er bolt right on to my mid? The front half of the case is the same right?

[Lil' Blue Rude]

56's have more low end torque. Yes the 49 cranks will fit a 56 block. The 56 should bolt up to the mid but you'll need the exhaust and powerhead adapter plate for the 56 cube.

[LittleCharger]

The 56er will bolt up to the mid, you will have to do a little grinding on the inside of the mid to create a little clearance in order for the 56er adapter plate to fit. The 56er power head bolts are larger so you will have to drill out the bolt holes on the mid also.

As noted above 49er crank will fit 56 block, and yes the front halves are the same.

Both are good motors.

[camohunter]

Is the adapter plate for the 56 something aftermarket you buy to make the poweRhead fit?

[LittleCharger]

There are aftermarket 56er adapter plates, either the sst60 adapter plate and tuner from Seaway or HeviKevi here in Ontario has nice billet machined ones with tuner.http://www.boatracingfacts.com/forums/showthread.php?16504-56ci-custom-cnc-d-adapter-plate-and-tuner-for-49-stinger-swap

The less expensive route is to simply grab a adapter plate off the long shaft mid section that the 56er power head came off.

[camohunter]

What is the difference between the aftermarket adapter plates and the stock plate off a long shaft mid section? Is it something with the drive shaft length or the exhaust tuner?

[LittleCharger]

What is the difference between the aftermarket adapter plates and the stock plate off a long shaft mid section? Is it something with the drive shaft length or the exhaust tuner?

Aftermarket has solid motor mount incorporated in adapter plate, SST60 spec tuner which is an upgrade over cut off stock tuner, Kevin's adapter plate also allows wing plates to be bolted to adapter plate versus head bolts

[camohunter]

Thanks guys for the good information.

[Fast Fred]

Stinger intake ports are in a high state of tune, finger ports add about 10 hp

[camohunter]

Stinger intake ports are in a high state of tune, finger ports add about 10 hp

Finger ports are one the intake side right? I saw where you marked yours with the dye. Do you cut your own or send to a machine shop. How the hell do you get in them cylinders to cut?

[Fast Fred]

would need to know what hull you got, and what you plan to do with it, if your goin to roll a bull moose less the gut pile into the bow, peak hp is not what your lookin for...............

[camohunter]

It will go on a 16' aluminum boat that weighs around 300 pounds. They've got one now with a sort of vee pad hull like a bass boat. I've got a 30" tiller handle that I may put on it. I will often have a passenger and gear.

[Fast Fred]

if it was mine i would not jack up the ports, they get peaky, go with a tuner out of a 20", the big lower unit may be better, or put a 3cyl drive shaft in a 2cyl nitro foot, rev limiter box,so i could run most timin for the out of the hole punch, finger ports would still help it,...............the big lower be easier to find props

[Fast Fred]

you can always do what ever you want, i've done all the combinations on many diferant hulls over the years.............

[MGR]

Hey
Fred

I am try to tune my 56er it dies off as I try to come on plane.
What should the ideal and wot Timing be?
Where are the jets on the carbs the one in the front is the low speed right?

O the motor is a 56er with 160 compression fiber reeds and one of Kevin's built tuners
With a nitro case. The boat is a 13 Allison t850 race boat.



Thanks mike

[25XS]

I am trying to tune my 56er it dies off as I try to come on plane.
What should the ideal and wot Timing be?
Where are the jets on the carbs the one in the front is the low speed right? Thanks. -Mike

Mike, if you don't own a factory service manual for your engine, snag one off eBay. The OMC manuals are written very well, include special tools lists and how to use them, and pictures of the proper wire & hose routing to avoid damage from pinch or vibration/chaffing.
Your engine exhibits the symptoms common on this engine where a proper "Sync & Link" procedure should be performed to synchronize the carburetor butterfly opening to the ignition timing advance. Be sure (both?) the roller & sleeve assembly has the clear plastic cover on the throttle & timing cams (not just the black, plastic roller). The "Sync & Link" procedure is described in great detail and too long to post here without the photographs the factory manual includes.
If, after the Sync & Link is done your boat still falls flat on acceleration, start opening up the idle jets to make them fatter. You can 'goose' your choke when this symptom occurs and it it improves then you're likely starving for fuel on acceleration and need to richen the idle (& mid?) circuit.
Hope this helps... Worked on tons of 3-cylinders on fishing boats & pontoons. They need to be set right to accelerate smooth.

[LittleCharger]

Mike, if you don't own a factory service manual for your engine, snag one off ebay. The OMC manuals are written very well, include special tools lists and how to use them, and pictures of the proper wire & hose routing to avoid damage from pinch or vibration/chaffing.
Your engine exhibits the symptoms common on this engine where a proper "Sync & Link" procedure should be performed to synchronize the carb butterfly opening to the ignition timing advance. Be sure (both?) the roller & sleeve ***'y has the clear plastic cover on the throttle & timing cams (not just the black, plastic roller). The "Sync & Link" procedure is described in great detail and too long to post here without the photographs the factory manual includes.
If, after the Sync & Link is done your boat still falls flat on accelleration, start opening up the idle jets to make them fatter. You can 'goose' your choke when this symptom occurs and it it improves then you're likely starving for fuel on accelleration and need to richen the idle (& mid?) circuit.
Hope this helps... Worked on tons of 3-cylinders on fishing boats & pontoons. They need to be set right to accellerate smooth.

Solid advice!!

Mike maybe we can hook up and I can help you get things sorted out. I can meet up with you in Dunnville (ramp or Jeremy's), I'll bring my test wheel, timing light and some props for you to test.

[DeanFHobart]

Make sure the Drive Shaft does not bottom out in the spline...... Binding will occur. There needs to be some clearance..... Maybe .125". Maybe more..... Whatever the stock set-up is.

Good luck in your mod.

[Fast Fred]

20 deg max on a 56er , not goin to find that in a manual, when she falls on her face goin from low speed circuit to high speed circuit is a sign that she needs more fuel to make the jump, to get mo fuel in the low speed, open low speed mix screws or bigger low speed jets, the low speed is in the top front of the carb, with ether a plug, a needle or an air jet.