Re: 1988 glasstream 275 volvo penta 4cyl
Probably a bad prop. They have rubber hubs that can go bad and cause your exact problem.
That would be the most probably cause. But a slipping clutch cone in the drive or a shift cable out of adjustment causing the cone to slip could also cause it also. Was the oil on your dipstick milky? If so, that's water, which will also cause it.