Got a wierd one here and I am stumped. Working in a buddy’s boat this weekend. He bought a bare hull and stuck a 496 and Bravo 1 drive in it that had been sitting around for a while.
Interesting thing is it will run fine for several mins then slow down then seize. Hit the key and seems pretty well seized. Let cool for a few mins and it’s good to go again. No funny noises. First Thought was water reversion and hydro locking but it happenes even at 2000+ rpm. Plus pulled plugs and no water.
Any chance the starter is maybe not disengaging from the flywheel and pulling motor down after it heats up? And do so with out making any unusual noises?
Anything other random thing to think of? Oil pump maybe? Something in the upper half of the drive? Valve stems sticking on guides? Pistons skirt or wrist pins? Spark doing something funny and jumping a cylinder ahead? (Did try different MSD box and coil )
It’s got great oil pressure, and nothing funny in the oil on the dip stick. The problem pulled the motor down from around a constant 2000 rpm yesterday even. But yet two weeks ago the motor ran for around an hour on the hose and never had it happen.
Any help or ideas?