1985 50 hp force, hard turning over

hello i have a 50 horse force that hasnt started for me this year. at first i thought it was the starter, I cleaned all the grounds and continuted to all power connections, replaced the soleniod and batter cables still have the same problem. the engine will turn over with the plugs out. once i put the plugs in it will maybe turn a quarter of a turn and stop. i checked exhaust to see if it was plugged. no obstruction, removed the lower unit to rule out the gear box. still it will turn over excellent without the plugs and once the plugs are in only a quarter of a turn and stop. bought a new starter today for 200 and same plus i know i have a new battery. can it be a bad bearing? flywheel does have a little play in it from counter clockwise to clockwise. i pulled the fly wheel to make sure the shear pin wasnt the problem and that is fine. any input is greatly appreciated as i am a 99er and have no income to purchase another motor, thanks stranded in Green Bay........Stephen

It might be that your "new battery" is not holding a charge properly - any chance you can hook up another battery that is definately known to be good (even pinch the one from your car to test things).

If that makes no difference then I would try to turn it over manually (should have an emergency rope start) with the sparkplugs in.

Before you start tearing into the guts, best to rule out causes "external" to the powerhead itself.

It's much better to determine it's simply a bad solenoid "before" you are standing there with the crankshaft in your hand, than after

ok done all that last nite in the garage after my post. this morning got the crank case open and found the crankshaft broken in half between the upper thrust bearing and the top connecting rod. i just bought a donor engine this morning that has no play but the compression is low. gonna make one of out two hope it works. thanks

Stephen