Mobil 1 0w-40fs flat tappet mercruiser 350

[OVERKILL]

There was never a roller Windsor used in marine engines. I’ve been inside several GT40 PCMs myself. The blocks were roller capable but ran flat tappets (like the 351 in the lightning truck).

Oh, now that's interesting! Too much time on the Mustang 302's, which were roller a decade earlier. I assumed 1995 would be roller, since it was already late EEC-IV.

 

[Zap1967]

Oh, now that's interesting! Too much time on the Mustang 302's, which were roller a decade earlier. I assumed 1995 would be roller, since it was already late EEC-IV.

Yeah, not sure why they didn’t rollerize the marine engines(or the lightning for that matter). The Fords are much more tolerant on ZDDP vs the big block Chevy. I’ve fed many 351s a steady diet of T4. One of which has around 2500 hours on the camshaft/lifters (was reused after a rebuild). So anything with reasonable levels will likely make it live forever.

 

[Chris142]

Chevy started using roller tappets in 1987. Would that not be the same for the Chevy - Mercruiser 350 Chevy engine. Maybe I’ve missed something. If that’s truly the case use whatever will pour in it. If it’s still flat tappet I’d go with a healthier dose of zinc - oil.

Not all engines got roller cams. I replaced several intake gaskets on 5.7's made in the mid 90's in trucks that were factory flat tappit cams

 

[OVERKILL]

Yeah, not sure why they didn’t rollerize the marine engines(or the lightning for that matter). The Fords are much more tolerant on ZDDP vs the big block Chevy. I’ve fed many 351s a steady diet of T4. One of which has around 2500 hours on the camshaft/lifters (was reused after a rebuild). So anything with reasonable levels will likely make it live forever.

Yeah, we had an old mid-70's Mercruiser 888 in a Glastron that was beat on like a red-headed stepchild and it didn't get anything special for oil, just basic GTX or VWB. The boat was scrap and the engine was still running great, similar hours to yours.