I have a stage 1 35 hp GTR on a heavy ass boat. At 9 hours it cracked the crank case and sheared off the dowl pin on the oil filter side. The crank case was replaced. At 11 hours the bolts became loose again, so i pulled them out cleaned them off and applied red lock tight and retorqued. At 14 hours the four bolts on the oil filter side sheared off in the block. Also the stock exhaust was cracked to hell and back in about 9 hours. It seems like something must be out of whack causing some kind of vibration that is shacking everything apart, but i don't feel that much vibration while driving. I would like to hear other peoples opinions on what it could be or if this is just what it is like to be a mud motor owner. At this point i really wish i would have kept my outboard at least i new it would get me back to the landing.

That's not part of being a MM owner. If it were a stage 3, it wouldn't be that uncommon, but a stage 1 shoudln't be doing that. More knowlegable folks will chime in.

Any other ideas. Also forgot to mention that the bolts on the opposite side of the oil filter have held fine.

Ony my stage 3 I had similar problems. I drilled and tapped them larger and use arp bolts. Held better but still came loose. I have put heli coils in and are holding fine now. Try that

IMsO ~ You are havin' way too much troubles. I gots 'bout 500 hrs on mines ... and knock on wood ..... I have not had those problems yet ..... muffler .. yes ... but not all that crankcase trouble. I live purdy close to you so it would be easy fo me to come look at it ... but thats 'bout all I could do .... I ain't much of a mechanic.

Who put the new crankcase on it fo you ??

Have you had the prop checked to make sure it's not out of balance? It's amazing how much damage that can cause.

Yes i have already tried another prop. I had the other prop on when it sheared to bolts off at 14 hours.

Who did your stage 1 mods?

^ agreed.

If it's bein fixed by a warranty, somebody's gonna start lookin deeper into it, if not, they're just gonna let ya keep dumpin ya $$$ into their pockets.

what about the prop shaft? could be slightly bent. Something is causing excessive vibration for the bolts to back out / shear off. One in a million, but what about the cam? Could be slightly out of balance.

Yes it has been done as warranty work.