Re: 454/310 motor replacement options
 

I spoke w/Bob today and it looks like we are gonna do the hp500. I thought for a second since he has an 830 prefix it was his home number. Spicewood is not to far anyway.

Re: 454/310 motor replacement options
 

Sorry if this is a dumbazz question, but is an HP500 motor an 8.2L 502ci rated @ 435hp out of the box? Please advise.
Thanks!
Dan

Re: 454/310 motor replacement options
 

I believe the HP502 has 470hp were the 502 mag isthe one w/ less power ( 415hp ). I think the 496 is the motor w/435hp.

Re: 454/310 motor replacement options
 

I believe it goes something like this....490 MAG is 375 HP, 496 MAG HO is 425 HP, HP500 is 470 HP, HP500EFI is 500 HP and from there is' easy as HP525EFI is 525 HP etc, HP575 SCi is 575 HP etc. etc.

That's for stern drives and is PSHP not flywheel HP. V Drives, not that it matters, is a little different since it's a different drive thus different parasitic HP loss.

Re: 454/310 motor replacement options
 

I have plenty of room in my engine bay and would like to reliably increase the hp when I repower without having to spend a fortune. Is the HP500 motor carbed and will it bolt into the same engine mounts as my 1989 carbed 454? What is the engine of choice when it comes to staying carbed and naturally aspirated? Thanks again!

Re: 454/310 motor replacement options
 

Jig,
The dimensions are the same. You have a good base for repower. By adding a stroker crank and possible heads, you can build a "500 incher" for the boat. Eagle, Scat are companies with affordable kits, Probe is another. These kits can be had for around $1400 to $2K in parts. Freshen your heads or add a set of Merlin Oval ports with a mild roller cam and you can build your self an easy 500HP/600#/ft engine.

RMBuilder, Bob, is real good with combinations and would be able to assist you.

Chris

Chris

Re: 454/310 motor replacement options
 

Interestingly, all of the Merc Racing engines are crank rated HP.

The HP500 carb and HP500EFI both have 500 hp at the crank, 470 at the prop of a standard Bravo drive... Even the HP500 Bulldog (a 540 ci) is 500 hp at the crank...

The HP500 carb will fit like a glove in the place of a 454 carb or MPI, whether mag or not...

Chris: I believe these couple of guys want a 'factory' engine complete, as opposed to building one. At least that's my understanding...

Kent

Re: 454/310 motor replacement options
 

You learn something new every day. Just hope I can retain it!! :D

Re: 454/310 motor replacement options
 

Of course, everything I have ever seen shows Merc Racing to be very conservative in their hp ratings!

Heck, there's a fellow on another thread here who is upgrading his HP500, and with 270 hours on it, it showed 530+hp on the dyno!!(if you believe the dyno sheet, as it even had leaking head gaskets)...

The least HP I have heard of in an HP500 has been 515. The most was close to 550!
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Hey SearayJim, how's your engine coming along??????
I sure would like to come over when Bob installs it!! That still blows my mind what you are doing to your little Searay!!!
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David, did Bob tell you the story of our first test/debug run of my Donzi after he installed the HP500? I mean about the race we got in?

Kent

Re: 454/310 motor replacement options
 

Jigsaw89,
Nice boat you have there. However, I would be carefull when adding considerable power. Make sure your engine mounts can take the extra power and stress that goes with it. Also, I would check with somebody that knows high performance boats to make sure the stringer system and the integrity of the boat is suitable for what you are going to do. Remember, boats are unlike cars, it takes a considerable amount of power increase to see a few miles per hour. Good luck!