HELP! Hit some serious mud today now motor won't start

[Npr9155]

I have a 1966 40 HP Big Twin, just got it running nice after a full ignition rebuild, carb cleaning fuel line and water pump rebuild. Took it out finally and hit some serious mud at full throttle very early on. Within seconds the engine died and wouldn't start back up even hours later. Took the lower unit off and cleaned out the pump to be safe. Checked spark, it was strong. Plugs were clean. Checked fuel, good as well. Compression was fine before didn't check yet. I'm new to working on motors. What else should I check? Has this happened to anyone before? Bummed after all that work first run was a bonehead move and back to square one. Anything will help thanks.

 

[boobie]

Check the flywheel key to make sure it's not sheared.

 

[jimmbo]

I agree with boobie. Those Big Twins had massive flywheels and pathetic keys.

 

[Npr9155]

Sounds good I will check in the morning. I sheared one last week when running it in a barrel. Fixed it and it started right back up. Should I be concerned with powerhead at all from hitting mud like that? Thanks.

 

[boobie]

The flywheel torque on that motor is 105 ft-lbs. If you don't have that it's real easy for the key to shear.

 

[jimmbo]

In 1974 we had our 1963 40hp tuned up. First time out after running less than 5 minutes at WOT, it felt like the motor struck something. It slowed down and finally stopped. Couldn't crank it, with starter or recoil. Got a tow back to the dock. put boat on trailer and began to troubleshoot. We found the flywheel had lifted up and was jamming the recoil housing. Removed recoil and found the flywheel nut was loose. Removed flywheel and inspected the taper, the key wasn't sheared but was now offset. Put back together, really torqueing the flywheel down. Ran OK. The old man took the boat back to the dealer and had words with them, but the b*****ds didn't seem too concerned about flywheels coming off.
Had one more experience with that dealer 11 yrs later. Took a motor in for some reason, when I went and picked it up, I looked at the repair invoice and had several questions about the parts replaced. There were several interlocks in the starter circuit replaced. I asked the owner why they were changing these, it was a rope start engine. I walked out of there 'no charge' even for the work I had asked for.