Converting Mecruiser to OMC engines

I am currently installing two OMC(5 litre) engines in my 27' boat to replace the old Mercs (3.7 litres). I wonder if anyone could advise me if there is an adapter available that connects the Mercruiser wiring harness to the OMC harness?

Appreciate any help or advice that someone could give me.

Cheers,

Queso

Re: Converting Mecruiser to OMC engines

Nope,... I'm sure there's No readily available Adapters to put OMC motors to Merc drivelines...

What you're attempin' is Strickly Custom...

Re: Converting Mecruiser to OMC engines

Its gonna need more than a adapter. Depending on the year of your gauges you might need new tachometers and you are gonna have to reuse all the sending units. Its actually not that hard to wire up Merc engines. You are gonna need to change things up for running your cooling/exhaust system, as well as the motor mounts...

Re: Converting Mecruiser to OMC engines

The OMC exhaust manifolds and risers will not match up to the Y pipe for Mercruser. Plus, and you don't have a Mercruiser Y pipe for a V engine. So you need a Merc Y pipe and hope it bolts up to the Merc 3.7 transom shield and has the proper idle relief ports. Then you will need Merc manifolds and risers to match up to the Merc Y pipe. The OMC man/risers have different angles.
The flywheel cover for OMC has the wrong kind of mounts for the Mercruiser inner transom shield. The 3.7L Merc cover will not bolt up to a 5.0L engine.
The gear ratio in the drive is wrong for the 5.0L engine
The OMC coupler is not the right one for Merc, It may work, if it fits under the Merc flywheel cover.
The shift interrupt system from the Merc is needed, the OMC will not work.
You will need stringers of the proper height for the side front motor mounts on a V engine. There is no front mount like the 3.7 has.
You will have to change some of the wiring, the plugs are different, not a big problem compared to the other things you need.
Other than those small items, it's a direct bolt in

Re: Converting Mecruiser to OMC engines

Thanks for all the suggestions and prompt replies. I didn't express myself very well the first time. I have removed the old 1988 Mercs with the legs and the transom mounts. I have installed the 1986 5 litre OMC engines complete, with transom mounts and legs, in otherwords the whole package. What I need to know is if I can use the Merc controls and cables that were attached to the 3.7 litre engines with an adapter or do I have to cut the plugs off the old Merc and the new OMC and make up some kind if bus bar that I can use to match up the various circiuts. I hope this makes the question a little clearer; I'm sorry that I didn't explain the situatiion more clearly.

Cheers,

Queso

Re: Converting Mecruiser to OMC engines

Wait a minute, you're telling us that you are going from 470 Mercruiser/Alphas to 5.0 (Ford?) OMCs with Cobra drives?

Talk about leaping from the frying pan into the fire!

Re: Converting Mecruiser to OMC engines

WOW!!!

You should have stuck with Mercruisers. At least parts are still available for 470's and the Merc drives...

Re: Converting Mecruiser to OMC engines

Queso said:

What I need to know is if I can use the Merc controls and cables that were attached to the 3.7 litre engines with an adapter

Click to expand...

you may be able to change the throw of the shift, but i'm not sure the length of the throw is the same for merc/OMC - same goes for throttle control

best off to get OMC controllers

Queso said:

do I have to cut the plugs off the old Merc and the new OMC and make up some kind if bus bar that I can use to match up the various circiuts.

Click to expand...

you may be able to cut the cannon plugs from the mercs and splice the wires, they are color coded

if you have the OEM manuals for both engine/drive packages, it might be possible - don't know if it will work though - you got a project ahead

i hope you got the OMC packages for a song, otherwise, it may have been better to go with a single big block/drive package and spend the extra cash on fiberglass work

Re: Converting Mecruiser to OMC engines

dubs283 said:

you may be able to change the throw of the shift, but i'm not sure the length of the throw is the same for merc/OMC - same goes for throttle control
.....

Click to expand...

I'm using the factory OMC shift/throttle controls & cables from my '84 stringer, they're now connected to a Merc Alpha gen 2 setup that I converted to, it works perfectly.