OMC Engine Coupler 5.7 liter

[OMC & ME]

Replacing engine and ran into a problem with the bolt pattern on the new crankshaft end and original fly wheel and coupler.
In other words the new crankshaft flange is larger and with a wider bolt pattern than the old .
Flywheel center hole (2 3/16 ID) is to small to fit the new crankshaft flange center hub and bolt pattern is way off on both the old flywheel and coupler. Looks like a new fly wheel center hole will have to be 3 5/8 ID. and the correct bolt pattern.
Would anyone know if there is a flywheel and coupler that would fit this bigger crank flange?

 

[Scott Danforth]

First, welcome aboard

Second, most likely you are trying to replace a 1-piwce RMS motor (1986 and later) with a 2-piece RMS motor (1985 and earlier)

 

[OMC & ME]

Thanks for the welcome!
Yes sir the replacement engine is an older one with a fresh rebuild. What could you tell me and who may be a good contact
to purchase a flywheel and coupler to fit this older crankshaft?

 

[Scott Danforth]

I would get the correct motor to start with.

OMC changed the style of drives when the motor designs changed. that is, the cobra was designed and cam out in 1986 with the change to the engines from GM

there is no 1-piece RMS couplers for the stringer style drives

there is no 2-pices RMS coupler for the cobra drives

the flywheels are easy, its just a GM truck flywheel for manual transmission.

 

[kenny nunez]

When you are purchasing the flywheel be sure that it is the same diameter. You also might be able to use a coupler that bolts to the clutch face bolts like Mercruiser has. Your only other style of coupler is the earlier style Mercruiser type used that bolted to the crankshaft, these were used on every Mercruiser GM 4,6and small block V8 engine from the 60s - to when GM went to the full circle main seal. The spline count is the same.

 

[Bondo]

Replacing engine and ran into a problem with the bolt pattern on the new crankshaft end and original fly wheel and coupler.
In other words the new crankshaft flange is larger and with a wider bolt pattern than the old .
Flywheel center hole (2 3/16 ID) is to small to fit the new crankshaft flange center hub and bolt pattern is way off on both the old flywheel and coupler. Looks like a new fly wheel center hole will have to be 3 5/8 ID. and the correct bolt pattern.
Would anyone know if there is a flywheel and coupler that would fit this bigger crank flange?

Ayuh,..... Welcome Aboard,..... Sierra makes a conversion coupler like that,.....

I just answered this question for Distein, yesterday over at marine engines,.....
The number he has is Sierra 18-2172 coupler

 

[OMC & ME]

Hey Bondo, Thanks for the welcome and the info. I'll give it a whirl and see what Sierra got to offer.
Thanks again!