snake plissken

Hey what can i do to give me about 500 H.P I have a few external bolt on stuff which im sure has givin me a bit more than 310 Hp first i added a K&N air filter then i added a jacobs ignition system theni just bought a set of dana flo headers. can really say afterdoing that stuff i feel any more H.P runs the same Top end. by the way i have a 1999 Donzi 22 zx steped Hull bravo 1 24Pitch runs 58 GPS 22P runs 55 GPS at about 4200 alivation my goal is to run in the high 60's or low 70"s. Im looking for a new cam and head work will this achieve my goal? thanks Vince
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Dave M

1. Remove 454 MPI
2. Sell 454 MPI
3. Buy 502/500 HP

Not trying to be a smart a$$ but those 454's do not have the internals to make tons of power. You can probably sell the complete motor and buy something else.

Whiteknuckle

Is that Donzi a runabout or cruiser hull? There is something wrong with your speeds/engine RPM with your props. If you are only turning 4200 RPM with the 22P, the last thing you want to do is go to more pitch. You should work on getting that engine up to a minimum 4600 RPM with the 22P. I am not familiar with the Jacobs Ignition but are you sure your timing is set correct and you are getting proper advance? If your engine is in a good state of tune, maybe try a 21P Mirage prop.

East Coast B

The 310hp 454 is a weak link... period... Doesn't have the internals for taking more hp, usually they blow if you try to change out various parts. You would need to start from the bottom up with rebuilding that motor... Been there, done it... boom! I agree with Dave above as well, drop in another motor, the 502's are very reasonably priced... or take your engine out and rebuild from the bottom up... crank, heads... everything..... I personally would go the 502mpi route if money is a concern.... look around, they are priced right since the 496 hit the market.... if money isn't an issue, drop in a 525efi.... and hold on! Good luck!

dyno

it costs as much to upgrade as it does to buy a mill outright...sell what you have keep your accessories, sea water pumps and such and buy a crate motor off ebay and ahve a good builder assemble it. Take it from me I just got done with my 330 upgrade....

Payton

I think he said he is at 4200 elevation, not 4200 rpms.

SeaRay Jim

Ben there, done that. Do a search and you'll find 2-3 good thread on this. I had mine done and the only thing that would have gotten me a better outcome would have gone to a carb. You can get a lot more power out of it but you're going to spend a lot, and what you get just won't be worth it.

The above advise is good. Pull the 7.4, replace. Sell the 7.4 for the $2k-3k you might get for it if it's in good shape, to someone that has a cruiser that nees to replace a motor.

I don't have pics of it, but bobl and I split the 2 pieces of a piston that was left of mine. I got the rod too. bobl has the block with a hole.

I now have a 540 (built by bobl) and can now appreciate a real increase in power.

Whiteknuckle

My point I was trying to make and did not do a very good job of, was to get the most out of what you have first. I agree that getting 500 HP out of that engine takes much money and time. However, there appears to be some room for improvment with what he has.

baronbob

I am surprised that know one recommended a Procharger. Especially @ elevation. I went from sea level prop 22" on a bravo III 4400RPM to a 26" 4600RPM. If you have the hull the speed will go along with the prop/RPM differences. I bought mine on this website for $1700 and lucked out as it was previously on my same year/model 7.4MPI. Cheapest Horse power I ever bought.

scottwilson48060

I am trying to restore a Frankenstein mess and have the same engine mount but due to my oil pan size this mount will not fit. I am wondering if I am looking at this wrong or is it all about oil paq capacity. What capacity oil pan are your engines equipped with?
Thank you for your help.