Mariner vibrating and prop question

[cc]

" Its a 1986 175 Mariner. I w

" Its a 1986 175 Mariner. I went out yesterday and it seemed to be vibrating more than usual. I trolled abount an hour and then did some drifts. It started up and went with out a problem. When I was coming in, it all of a sudden felt like it was slipping. The motor was vibrating at lower speeds about 2000 rpms. But I throttled up and was able to get it to 4500 rpms without a problem. It seems to do it at certain speeds (the vibration). I put the boat on the trailer and put the engine in gear. I can easily spin the prop. Is this a problem? Should the prop be hard to spin when it is in gear? Please help. Thanks! "

 

[tonyob]

"cc,

It sounds like the hub

"cc,

It sounds like the hub is spun. If you can turn the prop, and the prop shaft does not turn with it, the hub is definitely bad.

Newer props have a replaceable hub ( Michigan props ). If you have one of these, you can replace the hub easily. If not, I would advise you to replace the prop with the new style from Michigan. The replaceable hub is a nice feature to have.

"

 

[CC]

" Just an update. I removed t

" Just an update. I removed the prop and it is not spun. It looks good. I can actually turn the flywheel when I turn the prop in gear. Can bad gass make an engine tremble and vibrate so bad? I'm not sure if its bad, because I couldn't find any water in the gas. Thanks "