Whassup

My current boat is powered by a 502 efi and it has 250 hrs and seems fine but of coarse i want more speed, I was thinking of putting in a HP 500 the one I found is carburated is there any issues in swicthing and is it a good/bad idea. what MPH gain should I expect? or am I betteroff building my 502? my boat currently does 70 on gps. I also like having the silent choice which I assume I would loose with headers?? Thanks

laster

Your engine is basically the same as the HP 500 on the bottom end so it is a good candidate for upgrades to the top. It is not difficult or terribly expensive to build your engine up by 100+ horsepower. Heads (or head work) valve train, cam, exhaust and carburetor will go a long way in the direction you want to head. As far as the silent choice - the answer is "It depends" mostly on your cam choice, a big cam will probably leave you with a reversion problem if you keep the silent choice. The brand of headers will affect this as well but someone else will have to help out here as I am not too clear on which ones work well and which to avoid. BTW, what do you have for a boat and where are you? Just curious.

Larry

laster

Also, you might want to check out the thread on upgrading a 502 in the Technical Q & A section.

deboatmon

I really like the broad power and torque range from the EFI. I also like the ability to idle endlessly with no problems. I also like the smooth operation at any operating temperature. Fuel economy in my application is better than before too. I previously had twin 454's with Team G intakes, cams, carbs, Stainless Marine exhaust, and I have better fuel economy with better power now than before. I also have several mods done to my EFI's. From ECM, to heads and complete valvetrain. They are not stock. Upgrade ECM, cam, lifters and add roller rockers and you will see big difference. I also added Inconel valves and had minor head work done.

I'll never go back to carbs. It's pretty easy to duplicate the HP500 internal mechanical specs for your EFI. It's also no problem to get even better power.

Good luck.