Gen VI big block flywheels ?
 

I am starting a project to replace a L29 310 hp Gen VI 454 (2000) with a Gen VI 454 MPI 385hp (1998). One of the things I tripped up on is that the flywheels are listed as different part numbers. But I was told by an experienced mechanic that they can be swapped.

I think the 310 hp has a cast crank (not sure) and I know the 385hp has a forged crank, so could this be the reason that the flywheels are different? Different balancing ?

Also, can anybody confirm that the 1998 454 Mag MPI has forged pistons ? Thanks in advance- I am new to this forum but an old hand in boating.

Yes, 385 hp Mag motor has forged pistons and does require a different flywheel than the 310 hp motor.
Eddie

Eddie, in a previous swap, I believe (but cannot remember exactly) that I used a 1987 330hp 454 flywheel on a 2000 crate engine 454-HO (420 hp). Honestly, I cannot remember if I bought a flywheel from the engine supplier (Marine Engines Inc, the 1800runsnew guys) or used the old flywheel.
What harm could come if I used the incorrect flywheel ? The engine now has 200 hours on it and seems to run fine and smooth.

I am going to try to dig up the receipt and see if I got a flywheel, but its been 7 years.....

dt,
I am almost certain the Forged crank 454 uses a different balance flywheel compared to the cast crank. I have the info at the shop, will try to remember to look at it on Monday.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Bill, thanks for looking up the info- PS- I used to live in Clinton, just up the road from you, but now I am in Howard County.

If the engine is not trying to jump out of the boat or if you don't feel a vibration in your feet, you should be good to go, after 200 hrs and no problems, it should be fine.

I don't think he has run the engine with the flywheel yet.
I think he just got the engine and it has 200 hrs on it and did not get a flywheel with it.

The 2 engines absolutely have different flywheels. I'm not sure of the amount of counterbalance in each. If it is more than 10 grams (which I'm sure it is), it will cause a problem in the motor.
Eddie

Actually, I have two different engines.

My first question concerned a used 454-385hp (like the 454-HO crate )ngine and if I could use the flywheel from a 454-310hp Vortec L29 engine with cast crank. It seems the answer is no because of the different balancing.

My followup question was that I did a similar swap in 2000 using a 2000 454-HO marine crate engine- forged pistons, forged crank etc. But I cannot remember if I used a flywheel from a 454-330 hp (1987) which I think had 2 bolt mains and cast crank, or a got a new flywheel for the new engine. It now has 200 hours on it and continues to run fine.

In any case, I need to find a good flywheel for the 1998 454-385 MPI engine. If anybody has a good cheap flywheel for the forged crank, let me know.

Well, I called Marine Engines Inc and spoke to Dave, and it turns out that he found my sale in the computer and it turns out that I bought the correct flywheel with my 2000 engine. So no danger there.
Dave told me that he was under the impression that it was more of a Gen VI to Gen VI issue with the flywheel- more to do with the 2 piece rear main seal vs. 1 piece seal, but when I pointed out the different part numbers between my 2000 L29 engine and the 1998 454-385 MPI, he was stumped.
I guess I need to do some more research.

DT,
I forgot to look today :( I am sending myself an e-mail reminder as soon as I write this.

Bill K