4.3 wont turn over after new fuel/water filter

Boat started 2 months ago then sat. I put on a new fuel/water filter on (filled it with gas and hooked an electronic gas pump between tank and filter to push gas through) still wouldn't start. The engine turns about 1 time then there is a loud grinding and stops spinning, sometimes the belts even kick back. So I put in a new starter, same thing. I tried putting 2 fully charged batts on to start it and still same thing. I tried turning the crank to make sure the flywheel isn't missing teeth and I looked at it when I pulled the starter, looks ok. So I'm really looking for ideas as I need to get this thing winterized asap. One other note, as I spin the crank with a wrench I can hear what almost sounds like air leaking from somewhere.

Boats a 96 welcraft with a 4.3 mercruiser I/O

Re: 4.3 wont turn over after new fuel/water filter

Just tried bypassing the oil pressure switch, The crank does feel kinda hard to spin with a wrench.. still nothing but a grinding sound

Re: 4.3 wont turn over after new fuel/water filter

Try pulling the spark plugs to check to water in the cylinders, if no water and still boound up, pull the drive.

Re: 4.3 wont turn over after new fuel/water filter

Just pulled the spark plugs and turned it with the wrench again.. its a lot easier.. I let the starter crank the engine over a bunch of times and it didn't have any trouble, so its not locked or anything. I'm gonna let it sit for a bit, clean the plugs and give it another go. I'm wondering if I'm slipping off the flywheel under pressure cause the bearing is going?

Re: 4.3 wont turn over after new fuel/water filter

One step ahead of you, great minds think alike, no water but there was some gas so thats good.

Re: 4.3 wont turn over after new fuel/water filter

Got it!!! The spot where you bolt the starter to the motor was actually cracked!!! So whenever I'd go to start it it would actually move out of the way of the flywheel. Once I noticed it I had my dad put the one bolt in and use a crowbar to hold the starter over.. and of course she started right up! So after all the headaches and money spent to figure it out, it was that simple. Now I just gotta figure out how to fix the broken area on the engine block so I can keep the starter bolted up right.