Mercruiser 454, 1988 and 1996 Questions

[25thmustang]

I recently purchased a 1988 Sea Ray with a Mercruiser 454. Turns out the engine ingested water and is locked up at the moment. I’m working to free it, but stumbled on a 1996 Mercruiser 454 for sale. My guess is the 1996 model will bolt in making sure to use the earlier model exhaust components. Are there any other differences I may not be aware of? Is there anywhere to research what could possibly be different and cause an issue putting the newer motor in?

Thanks in advance.

 

[alldodge]

Should bolt right up. Exhaust will be no issue, only thing that might be an issue is if the bolt holes for attachments (ALT, PS, etc) holes are different size or other spot

 

[tpenfield]

Agree, should bolt right up . . . Do check the main wire harness connectors between the 2 engines to make sure they are the same . . . they might not be.

The 1988 454 is probably based on the 'Mark IV' version of the 454 and the 1996 4564 is probably the 'Gen 6' version. Both carburated engines (right?)

Check the wiring diagrams (Google them online) for each engine to be sure of any wiring/connector differences.

 

[25thmustang]

Both Carb engines. The 1996 is being sold as a Gen V not VI. The 1996 has no manifolds and risers so those will be new. The accessories come with the 1996 motor as well.

 

[Scott Danforth]

Both Carb engines. The 1996 is being sold as a Gen V not VI. The 1996 has no manifolds and risers so those will be new. The accessories come with the 1996 motor as well.

then its a 1995 motor. the Gen V was 1991-1995, the Gen VI is 1996-2000

 

[25thmustang]

Ad says it came out of a 1996 Sea Ray, so it’s possible it was a 1995 motor in a 1996 labeled boat. That would make sense.

I’m being told the engines are balanced differently, one being balanced up front and one via the flywheel. Also the current 1988 has an Alpha 1 behind it and I imagine the 1995/6 has a Bravo. Is there anything engine wise on the 1995/6 motor that would keep an alpha outdrive from being used (the alpha gimble assembly and outdrive will remain on the boat).

 

[Scott Danforth]

you are lucky the Alpha is still behind the Big Block. 1988 and 1989 were the only years and mostly SeaRays..... and that was discontinued because the big block torque usually shredded the Alpha and warranty was high

which heads are on the Mark V motor? if its rated higher than 330hp, you will most likely take out the Alpha

yes, the Mark IV block was a 2-piece RMS motor and the Gen V/Gen VI/Gen VII motors are all 1-piece RMS motors. both are externally balanced, however balanced different. the issue is the crank flange on the Mark IV motor aids in balancing the crank, where on a Gen V and later, the flywheel balance is changed. while you can physically bolt it up, do not use a 1-piece RMS flywheel on a 2-piece RMS motor or visa-versa.

does your 1988 motor have a 153 tooth or 168 tooth flywheel? most likely the 1995 motor will have a 168 tooth flywheel

 

[25thmustang]

Yes the alpha behind the big block is a terrible idea, but changing it is not a project that will happen with this boat.

As far as the tooth count on the flywheel, not sure. The existing engine is in the boat and the possible new one is for sale locally.

Does the way the engine balance Is done make a difference in bolting it in to the boat? The goal would be a complete drop in of the newer motor to the existing hull with the alpha assembly. I wouldn’t be swapping out parts between the two.

 

[alldodge]

If the 96 motor is drop in read less exhaust, then no need to worry about it. Drop and go