Omc to mercruiser

[Jtaylor28752]

I've got an 87 thundercraft with the 4.3 omc on it. It meeds a new motor and i was wondering if I'd be able to swap just the motor thats a 4.3 mercruiser onto it without having to change outdrive or transom plate or anything

 

[Scott Danforth]

welcome aboard

assuming you have a cobra drive vs a left-over 1985 stringer and motor

you only will use the long block as it left GM

if you have a 1986-1988 Mercruiser 4.3, you will unbolt everything mercruiser from the GM long block and then build up as an OMC motor

you would also need to convert the exhaust from the batwings on your OMC to the later 2-piece kit from Volvo

at that point, it may be faster/cheaper/easier to start with a GM 4.3 truck motor

however keep in mind, your motor is a generation 2 4.3 V6 - (1 piece RMS crank, non-roller, non-balance shaft). to keep things easy, you would want to stick with a 1986-1988 motor

however if you have a newer Mercruiser 4.3. I would scrap everything OMC in your boat, bolt in the mercruiser transom shield, motor and drive and mercruiser controls

 

[Bondo]

I've got an 87 thundercraft with the 4.3 omc on it. It meeds a new motor and i was wondering if I'd be able to swap just the motor thats a 4.3 mercruiser onto it without having to change outdrive or transom plate or anything

Ayuh,..... Welcome Aboard,..... No, the fully dressed motors won't swap,......

Only the Long Blocks are the same,.....

So strip the merc motor down to the Long Block, then redress it with the OMC accessories,.....