onesickpantera

It's a tough call. I am considering doing the exact same thing. What I consider is reliability and resale. I can pull my own motor and install another easily. However, I cannot tear my motor apart, change the cam, reflash the ECU, etc, etc. Now I have to find and trust someone to do that. You read a ton of horror stories on this board about motor builds that go south which is scary. Also, I think a boat with a stock HP500 carb will be worth more than a boat with a modified MPI black 502 mag with 500 hp.

Maritime_Eng

500hp out of a 502 MPI canbe done with out a cam change or head work. All you would need to do if change exhaust, modify the intake, recal ecu, and add MSD ignition.

BGIII

Are you sure about that?

If so, it took a cam change, fully ported Dart Pro1 heads, roller rockers, raised compression and an improved fuel system to get the next 40 horsepower to make mine 540 horsepower.

onesickpantera

Interesting. First I have heard this. Everyone I have talked to says 20-25 hp gain max from "bolt-on" parts. Except a supercharger of course!

What exhaust? What is done to the intake? Is this something you have pesonally done?

Thanks

LostinBoston

Dean - I cant believe your going to a place thats trying to save manatees
http://www.hontoon.com/manatee.htm
unless they also have them on the menu?

Maritime_Eng

I am in the process of doing mine. I just bought a 1998 formula 382 fastech with twin 502 MPI. I have talked to Keith Ekert, Arizona Speed and Marine, and Inovation Marine.

They are all telling me the same thing. 500hp is do able with a 502 MPI. The long block is basically the same as a 500HP. The main difference is the cam and the Injection. The limiting factor to a MPI is the exhaust and Intake.

Change the exhaust to any good flowing manifold (stainless marine) +35HP

Change Stock flame arrestor, re cal ecu, MSD ignition, and adjustable fuel regulator +30HP

Extrude Honed intake manifold and shorten the intake runners +15HP

So this puts you just short of 500HP.

Maritime_Eng

Most of the lingenfelter engines really made more than what they were rated for. The 540 were closer to 550hp - 555hp.

The improved fuel system is just the extrude honed intake with shortened runners along with the adjustable fuel regulator (same as what I will be running).

The cam change will give you 10-15hp. The roller rockers give you 5hp and the heads give 20hp. The kieth eckert exhaust manfolds and the raised compression make up the rest of the difference.

My opinnion is that you have the best engine package ever made...........by anyone! I wish they were still in the marine market.

onesickpantera

Actually, IF those numbers are real that puts you over 500(about 525) because the 502 mag is 415 at the prop.

However, please don't take this the wrong way, but I don't buy those numbers. The 502 mag upgrades have been beaten to death here and on other boards for years and if it were that easy then everyone would have 500+hp 502 mags.

I'm sure there's some performance to be gained but I seriously doubt it will be close to an 80 hp increase.

Maritime_Eng

I know that mercrusier says that it is 415 at the prop, but a friend of mine had his stock 502 on a dyno last year before doing some upgrades and they were right around 415HP. I think that Mercuriser had a misprint in there advertising.

BGIII

dgduck13,

I would strongly advise you to speak with Tyler Crockett before you spend any of your hard earned money on this project.

BTW, my fuel system has an additional electric fuel pump and larger lines going to the engine along with the adjustable fuel pressure regulator and ported intake.

This guy is doing a Crockett setup:

http://www.hotboat.net/forums/showthread.php?t=98928