787 Starting Issue

[brushmore]

I posted this in the two storke boat section but had no luck and hoping someone over here might have an idea. I am two years into my Challenger 1800 restoration and have this one last hurtle. My starboard engine won't start. It starts turning over and the the starter disengages then spins. See my video below. The odd thing is that this doesn't happen with the spark plugs wires are disconnected.

This is the second starter and same issue with both starters. First was an aftermarket and then I switched to a rebuilt OEM. Battery is good since the port engine starts just fine. Tested the ground and it's good too. Also switched sparks plugs between the two engines so I know these are good.

Anyone seen anything like this before? Any other ideas for things to test?

 

[GGuillot]

The spark plugs connected or not should have nothing to do with it, weird that it does. I'd look at the teeth on the flywheel and double check how the starter is mounted to the bell housing. Just to rule out the starter, I'd swap the two around on the engines.

 

[NickCawks]

My 717 was having similar issues. Turned out that the crank was slowly giving out and ended with a completely seized rod