I have a 1976 Bonanza 18 foot with a mercruiser 888 Ford 302. I have had it running a few times and been repairing problems from the person I purchased it from. He didn't winterize it last year. Had the freeze plugs replaced and the exhaust manifolds replaced because they were cracked. Now when I turn it over it cranks but when it sounds like it wants to start the starter disengages and spins. I replaced the solenoid thinking that might be part of the problem but the same thing happens. What should I be looking for to solve this issue. When I had it running it ran great. This just started after replacing the manifolds.