Driving behind a pontoon today I noticed his 150 Mercury propeller spinning in the breeze so fast it was invisible. We were both doing about 65-70 mph at the time.
First opportunity I passed him and during a stop at a redlight a few miles down the road I told him about it because I was thinking that he might wish to consider the unnecessary wear on his lower end and the possibility ....(I don’t know about past decade Mercurys)... if the lower end was spinning it might also be spinning his impeller without the benefit of lubricating/cooling water. I suggested it might be a good idea to trailer with the engine in-gear... but also made it clear I wasn’t really knowlegeable about it.

I know that I have no idea if my (F150 Yamaha) prop spins at highway speeds... but I think I’ll put the engine in-gear just in case.

Thoughts anyone?