1996 evinrude 90hp Motor locked up

[dtwalters]

My 87 year old Dad has this motor. We rebuilt carbs and it turned freely and started briefly. We were using muffs with water on of course. But then it would no longer turn over. With the engine in forward gear you can put all of your weight on the prop, trying to turn the engine over by turning the prop clockwise and it will not bulge, even with all spark plugs removed. He pulled the Stbd head off and the engine will turn over easily by turned the prop with the engine gear. Put the head back on and it will not turn over, even with all spark plugs removed. You can not get to the flywheel nut easily on this model. Last month we tried to start this engine and the electrode on the upper stbd spark plug broke off. We noticed it fairly quickly and pulled the head. It put a small pit in the head and scratched the piston head. We cleaned up the the piston, head and rebuilt the carbs before trying it again. Any idea what may be happening here. This motor has very low hours on it.
Thanks for any Help

 

[ondarvr]

You will never be able to turn the motor over easily by turning the prop, it just doesn't work that way. So you really don't know if there's an issue yet. You need to turn the flywheel.

 

[jimmbo]

I will assume it is a looper since you say you can't access the flywheel easily. Remove the shields to access the flywheel, it is a lot safer than twisting the prop. you say when the starboard head is off the engine will rotate. Can it be rotated all the way thru 360 degrees?

 

[dtwalters]

Thanks for the reply ondarvr. We know that using the prop is not the best way to turn it over. We were able to turn it over using the prop before thogh with the head on and the spark lugs out. This engine has a cover on top covering the flywheel nut.Looks like we may have to remove this cover.

 

[racerone]

Axtually there is no big flywheel nut.----To me it sounds like a bearing issue and will be big $$$ to repair

 

[dtwalters]

Jmmbo , I am not sure. My Dad just said it turns freely with the head off by putting weight on the prop, but when he put the head back on it would not urn even with all 4 spark plugs out. Thanks for the reply

 

[dtwalters]

Racerone, Thanks for the reply.

 

[racerone]

If one piston is hitting the cylinder head you have bearing problems !

 

[dtwalters]

Racerone, I see what you are saying. The piston may be hitting the head so it can not complete it's cycle.

 

[Tim Frank]

When you say "my 87 YO Dad has this motor"...do you mean he just bought it?..OR....he has had it for some time and it has never worked.....OR.....had it for some time working fine but it now has issues....etc., .... etc.
Any back story would be a big help....a baseline is a great starting point.