dogturd21

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.

Young Performance

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

dogturd21

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.....

BillK

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

dogturd21

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.

hoozeyurdaddy

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.

Young Performance

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

dogturd21

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.

dogturd21

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.

BillK

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

Bill K