Hey, This is my first post on the forum. I've been reading back through some old posting trying to find any info on replacement valve springs for the 502 mpi mag from 1997. Just bought a Powerquest viper with these motors. they have just over 500 hrs on them. i've pulled the valve covers to fix oil leaks and am thinking now would be a good time to replace the valve springs. But I'm having trouble deciding what springs fit these heads. It's my understanding that comp cam make the springs for mercruiser? any ideas on replacement part numbers or specs for these springs. Thanks

Pretty sure stock springs are GM. It has a very mild cam (.483 lift I think) and the springs should still be fine at 500 hrs

Black MPI engines were designed to go 1000 hours before any major rebuilds. I just turned 1000 hours on my 502 MPI last season and yes they are going to be rebuilt soon, they spin up to the increased rev limiters at 5300 regularly and are happy.

I HIGHLY SUGGEST however pulling your fuel injectors and having them flow tested. I melted a piston one month after buying mine two years ago from a faulty injector. It is an easy job and is cheap insurance. The factory injectors suck and are prone to problems.

Agree with both above,,,, the 500HP/ 500EFI /525 EFI are the ones you want to do 250/300 hours. I wouldn't even look at that motor besides maintenance items for another 500 hours if you take care of it and dont overheat it.

Cool, will bolt the covers back down.
Thanks

Must depend how they are run. I went through 2 different 502 MPIs in different boats.1 was a 97 and 1 was a 2000. Both had rev limiters turned up to 5400. Both needed valve jobs and the springs were shot. Both however were in mild supercharged applications. One blew a head gasket and the other engines head gaskets were on the edge of failure.