brian valery

I am considering the purchase of a 502 MPI. The engine was in a 31 Formula and one of the engines blew. I am considering the purchase of the non blown engine. Exhaust and mans are new.
Anyone have experience with this engine? Pros? Cons? things to have looked at prepurchase?

Thanks
Brian

Vinny P

The first question would ask is why did the other engine blow? How many hours are on it? Merc hasnt made these engines for a while. The ones that are out there would have some time on them. If properly maintained, they should last a long time. If not, then the blow up. Generally, they are solid engines with few problems. One problem that comes to mind is that earlier ones ( not sure what year) had problems with the VST system screwing up. That would cause them to run very rich. What year is the engine?

lowfunds

who has the engine you are looking at cause i am on long island and i just pulled a set off 502 mpi's out of a 38 formula that had one blown engine. is the guy repowering with 496's. the big thing to look out for is the intake manifolds like to rot out in the back then the suck water in the intake ports and then grenade. i think that is the case with the one blown engine. these are not VST engine's they are cool fuel engines by the way. the lower intakes new from mercury are $1,700. i think there is someone that welds them back up and then makes them like new again.

brian valery

email me. [email protected]. I think the repower for the new formula is a pair of 525s. The boat is in Amityville.

Big Block Billy

Those 502 MPI motors had problems with the hydraulic roller lifters going bad. Have seen it with just about everyone that has had these motors. I would recommend doing a cam and lifter replacement with newer better parts. Hyd Roller cams have become much more durable in the last ten years and cam profiles have improved dramatically.
The aluminum intakes can easily be welded and re-machined. BBB

Outdrive1

I've also seen those fuel pumps go bad. They are part of the fuel cooler and come complete as an entire system, you can't buy the pump seperately. If the boat has been properly maintained, winterized so that they don't sit all winter with water in them, they should go a 1000 hours. no problem. They have forged internals, decent heads, and a tiny roller cam with stamped rocker arms. All really decent stuff for the 415 hp it produces. Make sure the riser gaskets are fresh.