I used them on a customers 502MPI with around a .600 lift cam from Marine Kinetics (Bob Madara). No reversion issues.

thanks guys for the replies, ive got my local builder doing the cam, he doesnt see a problem but I always like to do my own research too. I did speak with SM and didnt get a real solid answer on a "max" cam size because theres really so many variables. Guess ill try them and get it good and warm on the hose and just pull a riser and check. Can always add the extensions after. Any other input would be great, the more the better....

I have a local machine shop myself. But when it comes to marine cams there is knowone better than Bob RMbuilder. A lot of us here use him and he will know exactally what you need. There will be no quess work.

im in the middle of a rebuild and i have the stainless marine exhaust set up. the risers are stainless marine too, but how do i tell if they are short or long. Not to sound dumb, but what do yall mean by reversion issues?

With bigger cams sometimes water can actually be sucked backwards into the motor, especially at idle, the longer and steeper the angle on the riser the less likely. Its called reversion, do a search you can read for hours. If you have silent choice exhaust you probably have the standard risers, theyre not very long at all, if you post a pic someone can tell you im sure.