500 Efi To 625 Plus Hp
 

i have seen were the 500 efi has been upgraded to 625hp by Ron Potter and others. What is the correct combination to do this or more?

Don't bother...I did it, won't do it again. We didn't use anyone's "kit" but built our own (a couple buddies were the knowledge behind all the checks I wrote).

Made 540's out of the bottom end, ported Iron Eagle heads, BIG cam, 9.7 compression, monoblade ASM throttle body. The intake will hold you back. Dyno runs from seawater pump to my wet CMI's made 630HP and 700/ TQ. HP would have been higher (maybe 30-40) if we had went to carbs since the motor can't get enough air through the plenum. I was told all this but insisted on going EFI....It runs good but cost a fortune by the time we were done.

If you had started with HP 500's carbed to start with would you still say you would not do it again?

i know they changed the cam and heads, bumped the compression up and mapped the computer. left the motor a 502. ijust read on other thread Tyler Crocket was working on a new intake.

I have a new plenum top that will fit right on your intake manifold with a 2000 cfm throttle body built flush right in the top so the air will go right down the runners with on restriction. I plan on having one at the Miami Boat Show in Feb.

The main problem with mine is that we cannot use everything in the bottom end since we're not getting enough air. A buddy built 540's the same time I did and he had carb'ed 500's. Putting a bigger carb and air breather on his intake solved that air flow problem for him.....so yes, I'd do it again with a carb'ed 500.

do you offer a kit to get to 625 plus hp? how much? best time and way to contact you?

PM Thunderstruck. He has twin 650 hp from 500's and did the work himself. He's knowledgeable about it.

So Russ, you ended up going to carbs right? We'll talk in a couple of weeks.:p

I have a kit we have done several of these. Shop # is 8103242720 9-6

Pictures?

Why bother? You are taking a perfectly good motor that is worth a good bit of money and turning it into a pile of worthless parts. If you make a 540, what are you going to reuse... the block. Maybe the heads. You are going to ditch the crank, rods, pistons, cam, lifters, balancer and flywheel, heads and hardware etc. Even if you keep the heads you need to replace all of the hardware. Then a new intake plenum, throttle body, injectors etc., etc. etc.
If you have an engine that is in decent shape it will bring 11K-13K. I have seen ones in really good shape bring 15k plus. Sell it and put the money that you were going to spend into a new 650-700 hp engine from a builder (like me:D) If you split up your 500 and build it as a 540, you have taken an engine worth 12-15 thousand and turned into a pile of parts worth maybe a couple grand, if you could sell them. Good luck with whatever you do, Eddie.

For what its worth, I complety agree with Eddie. Or if you have the funds, keep the engine, then put it back in when you want to sell the boat. Factory Merc hp500efi will bring more $$ than some unknown carbed engine. Then you get to keep your custom engine. Just my 2 cents.

I wouldn't call it a worthless pile of parts but I agree....and I DID TURN MY 500EFI's INTO 540'S!!!!!!!! All I reused on the bottom end was the block, and the top (plenum, etc) is not large enough to accomadate enough air for big power (unless you force air). As I said before, mine run well but for what $$$ it took, I wouldn't do it again.

Supercharge that b*tch and be done or buy an Eddie engine!

I didn't mean wothless, as in not worth anything:D
The parts MAY be worth a couple grand, if you can find someone to buy them. That's still not much compared to the engine complete. If you only reuse the block, you are saving about 2K. If you get 2K more for the parts, that is 4K. Sell the complete engine for 12-15K. You are giving up 10 grand. Hope this helps, Eddie.

I agree with this, if your going through the hasle to stroke them then just spend 2,500 more on some Dart Big M blocks, then you still have the old ones for back up or to sell.

I have a carbed 500 and would like to make 650 out of it what needs to be done?

rotating assy, to make 540, decent iron heads 310 intake runner, a good MARINE spec hyd roller cam, 1050 domionator on good intake with 1" spacer, full headers, so that being said just make the check out to.....

Dave at MDG, took mine, stock bottom end, changed the cam, heads, throttlebody, injectors and fuel system as well as remapped the comp and we are at 8.8-1 compression, runs on 87 and at 615 hp and 670 lbs of tq. I love them, runs my tiger right where it needs to be and they idle like a champ. If I wind up doing a couple more 20 cigs, this will be the stock power for them.