engine swap issues
 

I have a 1993 nordic that was originally equipped with 330hp carbeb mercs. I was considering dropping a couple of used 502 mag EFIs in and was wondering what kind of issues Ill be dealing with. Any help would be appreciated, thanks.

it depends on the year but i would suspect none at all. it is essentially what i did to mine a few years ago. mine were 99 502 mag mpi. the efi needs high pressure fuel. mine had the cool fuel so the pump assy regulator etc was all part of it already. i put in a couple of carter electrics for lift pumps to supply fuel to two accumulators that then fed the cool fuel deal and ran the return line back to the tank. from there it was just plugging the wiring harness in and that was that. oh... and working on knowledge that i knew to be true NOT from the marine industry, i rewired the battery switches so that the electrical systems for both motors were completely isolated from each other so that there could be no possible way that the voltage reference that the injection uses could talk to each other.

FUEL RETURN LINE TO TANK,,,easy fix though.:ernaehrung004:

That engine is already equipped with the return line going back to the fuel filter head on the engine. You can leave it that way if you like. Depending on the year of the 502, some had problems with vapor locking. Merc came out with a upgrade kit to stop it. Basically, it was an additional fuel pump to help supply the engines fuel pump with fuel. Running the return line back to the tank will eliminate the fuel getting hot and vapor locking. The later year 502's with the cool fuel did not have this problem. That is the only issue with installing this engine. Everything should bolt up and plug in. Good luck, and give me a shout if you have any questions. I would be glad to help, Eddie.

Get the cool fuel system Eddie described. A dealer friend of mine has 2 new ones that he ordered for somebody that backed out on them. He will sell them pretty cheap. PM me and I'll put you in contact with him if you want them.

Thanks for the input guys. Im currently on a 1 year tour in Iraq and am researching my options when I repower. The boat had 622ci mountain motors when I bought it, but I dropped a valve so I sold the good motor and will repair and sell the other. Im not trying to be the fastest guy out there, just want a dependable trouble free package that will allow me to cruise 40mph all day, eat 87 oct and not destroy my outdrives. I may even install captains call diverters. I figure if I quiet it down, my wife wont be afraid to drive it. I should be ready to buy the engines when I fnish this tour. Im seeing some pretty good deals on low hour 502 mags. Thanks a bunch...........Casey

sandcraft, if u need anything from here hit me up i will be more than happy to help u, you r busting yous ass for us , we will bust our asses for you.

this is correct but its a bad way to do it. running the return back to the filter just introduces hot aerated fuel directly into the inlet.

feeding the inlet with fresh cooler non aereated fuel from the tank and putting the return back into the tank to cool off and lose the air results in a much better fuel charge being fed to the injector rail.

merc did it the other way simply for simplicity and packaging.

It works ok on a STOCK 502, as long as it has a fuel cooler. Merc did it, as you said, for packaging. I said that the best way to do it is to return it to the tank. That is the only way I do it.