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I have a 78 B31 with Mercruiser 454's, I have a spare set of engines and transmissions that came with the boat. I know the port engine is counter rotation, what I'm not sure of is, are the transmissions specific to the rotation of the engine, or do they not care which side they run on? I want to use one of the spare's and I'm not sure which side it came out of.

Anyone knows the answer?

Much thanks

The counter rotation is done by the transmission. All of your 454 engines are right hand turn....

Thanks Patrick

I know you know Bertram better than anybody but I'm pretty sure one engine does counter rotate.

I have a 78 with the original Merc big blocks, I know there is a different firing order on each engine and just to make sure I went to the garage and hand spun both transmissions clockwise and the output was clockwise on both. Am I missing something?

If the firing order is different than you do have right and left hand engines. Use that to determine which of the spare engines is ther one you want...

Thanks

I have the engine part of the project sorted out, my problem is I don't know which transmission came off which engine. Does anyone know if they are interchangeable? This the original,
I believe Borg Warner is the manufacturer.

Thanks

If the engines are counter rotating, then the transmissions are the same, (interchangable)...

Thank you!!

Those old 454's were counter rotating. I had a pair in a 1975. I don't think they did it through the transmissions until the 80's.

Borg warner inline gears cannot change rotation but for them to work the tranny pump rotation has to match engine rotation.
Looking at the gear from the front face you will see rotation arrows indicating direction. To change remove 4 bolts and just rotate 180 to the proper rotation. Do not remove pump housing just rotate.

454 engines did come in rh and lh. Only until they started using zf gears did the engine rotation all become lh.

That is a big help, Thanks much

Do the actual model number for these BW transmissions?

Thanks

I have had two different sets of 454s. My previous boat, a 1988 Formula 35PC with Borg Warner V drives, the engines were counter rotating. My 31 Bahia Mar has 1995 454. EFI MPs which both turn the same direction while my transmissions change the direction. I definitely prefer that because of parts availability, ability to swap anything between engines as a trouble shooting method and less spare parts needed on board.