took the engine apart today,502mag,mpi,1994.do i have a gen5,or6?my other boat has a 454,gen4,1989.in taking apart the 502 today i noticed that the rocker stud is diffrent from the 454.the 502 is a bolt.and the 454 is a stud.will the older style stud fit the 502?and will rocker arms interchange.i have a nice set of harland/sharp alumium rockers.they came off my 454 w/only 20 hrs on them.will they fit the 502?thanks.

The Gen VI 502 Magnum started in the 1996 Model year for mercruiser anyway. Serial # OF802600 and up. So it's a Gen V.

gen 5 has a 10 bolt pattern timng cover as the gen 6 will only have 6 easy way to check the two as all three generations have differant timming covers hope this will help

the bolt set up is the non adjustable [ net lash type ] you can replace them with the adjustable studs and use your rockers

I don't think the same studs will work. if I remeber right, the MK 4 heads use a 7/16 coarse bottom thread, 7/16 top thread.

The Gen V heads use a 3/8 bottom and 7/16 top. You just need to get the studs with a 3/8 bottom and 7/16 top to use your rockers. These are what you need.

http://store.summitracing.com/partde...5&autoview=sku

thanks guys for all the help.it is a gen510 bolts on the timming chain cover.and thanks griff about the studs.you are right.anybody know when gm started putting roller cam shafts in the 502,s.mine is a flat tapplet,hyd.also,do you think there will be any h/p gains if i switched to roller rockers.thanks.

Gen VI started the roller cam in Mercruisers anyway.