NoisePollution
would that not affect the fuel system?More CID - more fuel required?I couldnt imagine just putting a stroker crank without EFI remapping.
Ralph

Yep, there is more to it. There's a kit to make the fuel regulator adjustable. The Ecu has to be reprogramed. Mark at Precision Marine is good for that. $350 to reprogram. I used Dart Iron Eagle heads. While mine did run good, the biggest draw back is the 502 intake. Its restictive. The HP 500 EFI fuel injection flows better.
I'm looking for power so I'm changing over to a Dart or a Merilin single plane intake and a 850 Mighty Marine Deamon carb.The plus, I can tune it myself. Threre's a lot of Pro and con's here, but the carb wil make it simple.

Decided to stay stock for now since im rebuilding both engine and cash is getting low, but im preparing for the HP increase next year or so by installing New Forged pistons and Eagle H-Beam Rods And Manley Exhaust Valves now. he only thing im still wantingto do this year yet is Props and better Exhaust Manifolds. Any suggestions for these?
Thanx Ralph

Everything you might do for your motors is not always purely for more performance. Many things you can do are more for reliability than performance. Changing from stock exhaust is a great start. The difference in horsepower is not that great, but you add much greater reliability with regards to water problems in your boat and or motor. Personally I like the long, through transom risers from Stainless Marine with no hose and tips. And, If you opt for bigger cams later on reversion is virtually eliminated altogether. If you plan on cruising at 3500 RPM or above you might want to change the rockers as well. I've not seen too much written about replacing the stock air filter/flame arrestor on the 502 EFI's. You might consider adding a RACOR fuel filter if you have VST engines. The VST screen can really get fouled quite easily with dirty fuel stops and when fouled that motor is not going to run. I personally would add oil change lines to the oil pans to facilitate quick and easy oil changes. If it's easy it's likely you'll change more often.

Like I said, many changes are for reliability and not just performance.

I dont have a VST system on my 98 MPI's and im not too sure ill ever go all that radical on the cams.I'd be happy with 500 hp pr engine in the next few years.For this year 415 HP is gonna have to do

Thanx Ralph

The stock 502 MPI is a great engine package I believe. You have lot's of options and one option is to remain stock.

There's no bad options for your package.

Enjoy !

JIMG recipe
 

JIMG did you ever find that recipe...I need to freshen up my 502MAG and would like it to become a 500efi.:drink:




JIMG wrote....
I have to find the sheet. there is a whole recipe for doing the engine. will basically be a 500efi when you are done. runs real well and dependable

Tyler Crocket has a kit for the 502MPI engine that he claims is good for another additional 100hp. There was an article on it in Hot Boat Mag several years ago. I am going strictly by memory....

1) 2.25" stainless intake valves, and stainless exhausts
2) cut the decks of the heads about .020"
3) larger hydraulic roller cam
4) remap computer
5) larger throttle body and aftermarket airfilter (K&N?)
6) CMI elbow exhausts/headers

If I remember correctly Tyler didn't mention anything about any porting of the heads, so I would think just some minor clean-up in the bowl areas would be sufficient. Of course, I would always be tempted do some shortside radius work on the exhaust side. Also, I cannot remember if he brought up the cam specs, but I remember it being a pretty mild cam so that it works well with the MPI system. Last I knew computerized fuel injection systems do not like a big, choppy rough idling cam. If you buy the kit from Crocket you should probably expect to pay premium pricing.

With a little research and help from others on here you can probably piece it out part by part if you want to save a few bucks.

Also, you can call RMBuilder/Bob Madara of Marine Kinetics....he has been involved with some 502MPI cam upgrade projects as well. Bob's number is 585-654-8583.

You're most likely going to need an aftermarket exhaust system upgrade first if you expect to see any real power gains/differences. Have fun.

Already looking for cmi exhaust.Decided to rebuild motors and using eagle h beam rods and manley stainless exhaust valves and forged pistons/cranks.Getting both balanced so later all i need to upgrade is heads and injection/induction system

Thanx Ralph