1976 40hp engine won't turn over with plugs in

[Texasthb]

I have a 1976 40hp evinrude that just randomly stopped working. Thought it was starter so bought a new one and nothing. All new wires and new solenoid. If I pull the plugs out the motor turns over fine. Put the plugs back in and nothing. Starter won't turn over and won't disengage. 115 commpression on both cylinders.

 

[NiagaraRiverMan]

Did you try to keep the spark plugs in the wire with the metal of the spark plug against the metal of the engine case and turn it over for a quick second to see if they are actually sparking to see if you do have spark at all?

 

[Texasthb]

I have spark. No spark would just cause the engine not to fire. It's not turning over with the plugs in

 

[flyingscott]

Clean all your electrical connections VERY well and have your battery checked. Doesn't take much to turn the motor over with no compression which is the case with the plugs out.

 

[Texasthb]

I hooked strait from batter to starter with jumper cables and still the same. Battery is good and tried 3 different batteries

 

[oldboat1]

Did the motor overheat before it shut down?

 

[Texasthb]

It ran find when I took it out and took it home. Took it out the next week and nothing

 

[racerone]

Remove the lower unit and test again.

 

[kbait]

Can you turn flywheel by hand (clockwise) with plugs installed? (Remove plug wires from plugs for test). If not, are you using plugs w/too long reach (thread depth) that allows plugs to hit piston? Can't think of any other cause besides bad (new) starter motor that won't spin motor when jumped directly to good battery - but will easily spin motor w/plugs removed.. Unless it's hydro-locked, but you'd see a bunch of water (or fuel) coming out plug holes when spinning w/o plugs installed.
Good luck!