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Revelocity

11-11-2007 09:53 AM

Estimated horsepower on rebuilt 454 mag??

A friend just rebuilt a 1997 Merc. 454 Mag and kept it completely stock except for the below changes. Can anyone estimate what the horsepower is?

1. Rebuilt at .030 over
2. Compression ratio 10:1
3. BG SeaDemon 750 CFM Carb

All else is stock.

Thanks.

Payton

11-11-2007 11:37 AM

400

What kind of exhaust?

RBeyer

11-11-2007 11:53 AM

Quote:

Originally Posted by Payton (Post 2332481)

400

What kind of exhaust?

Agreed

KAAMA

11-12-2007 06:09 AM

I was thinking about the same....380-400hp.

chuckyarus

11-12-2007 11:58 AM

Don't you first need to know what the factory hp rating was on the motor or was there only 1 option that year, I know my boats older and there were 3 different hp ratings depending on the heads

Revelocity

11-12-2007 02:16 PM

Quote:

Originally Posted by chuckyarus (Post 2333242)

Don't you first need to know what the factory hp rating was on the motor or was there only 1 option that year, I know my boats older and there were 3 different hp ratings depending on the heads

There was only one "454 Mag" motor (with a carb) in 1997. The other motors were referred to the "7.4" and the "454 Mag MPI "(or possibly EFI instead of MPI). I believe the "454 Mag" was rated 350HP at the prop that year and the MPI variant at 385HP.

Griff

11-12-2007 05:03 PM

If all he did was bore it and up the CR and change the carb, he maybe added 30hp with the need to run high octane fuel.

Smitty

11-12-2007 05:07 PM

Should have changed the cam as well. That could bring another 30-50 hp.

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