Spin prop hub or engine coupler?

[Thompy_04]

My buddy has a 86 SeaRay Sundancer 270 with Alpha 1 drives X 2 and I'm trying to help him out. (I'm an outboard guy) While out we stopped for gas he pulled off and the port motor revved up. Starboard motor was fine. Worked flawlessly just the day prior no concerning issues, docked it, came back the next morning fuel up and it starts while we were getting on plane to leave. I'm thinking prop hub because I've seen it before but could a failing coupler show the same symptoms?

 

[Scott Danforth]

take a sharpie marker, draw a line across the prop nut and the prop. go for a ride, come back. if it is the hub, the line on the prop nut will have shifted with respect to the prop

 

[nola mike]

Failing coupler would show the same symptoms, as would a catastrophic drive failure (wiping out gears, broken drive shaft). If it's the coupler, the drive shaft exiting the engine will not turn with the engine on (or it might turn, but slip under load). Additionally, all but the prop hub will cause an overheat, as the impeller in the drive is no longer pumping. You can pull the intake fresh water hose from the drive to see if you're getting flow.

 

[kenny nunez]

Most of the time the engine coupler goes out you can smell rubber burning behind the engine.

 

[Thompy_04]

Thanks guys. Didn't notice any burnt rubber smell, but I did drain the lower and saw no metal shavings of any sort.

 

[wahlejim]

Do the hub test that Scott mentioned. At the very least, it eliminates the hub.