Whaler Central - Boston Whaler Boat Information and Photos

Posted by RMN on 10/02/11 - 6:52 AM

Currently own a 2010 170 Montauk with a Mercury 90 4Storke. Since new, there is a vibration/cavitation if you come up on plane slowly between 2600-3000rpms. If you come on plane quickly, there is no vibration/cavitation. Any thoughts or ideas? Dealer said they could not dublicate the problem in their test tank and said it is likely an issue that is inherent of the Mercury 4Stroke engine?

Edited by Joe Kriz on 10/02/11 - 9:18 AM

Posted by Eastend on 10/02/11 - 7:20 AM

Is the prop SS or alum?
Probably SS - which doesn't assist my point.
I have an alum. prop on a 90 2stk yamaha.
After hitting some sandbars, oyster banks, etc. and have an out-of-true blade, thus causing a slight low rpm vibration.

Posted by Phil T on 10/02/11 - 7:59 AM

I think RMN is experiencing a harmonic vibration.

On many boats there is a engine speed that causes a vibration that transmits to the hull. Some classic whaler owners hear it via the bow rails. on my boat, the GPS mount rattles.

If you slowly accelerate you will find the RPM when it stops and starts. It is not a major problem.

Cavitation has to do with the propeller. See
http://www.stingrayboats.com/products...q.html#p08

Edited by Phil T on 10/02/11 - 8:03 AM

Posted by RMN on 10/02/11 - 1:53 PM

Thanks for the info. It is a SS Prop. I've never experienced this type of vibration/cavitation on any other boat I have owned or operated. It is more than a sound, it is a vibration-some minor shaking when coming up on plane slowly (2600-3000rpm). I have no vibration when trolling or operating at any constant speed or rpm. Could it be an out of balance prop?

Posted by sosmerc on 10/02/11 - 6:31 PM

RMN wrote:
Thanks for the info. It is a SS Prop. I've never experienced this type of vibration/cavitation on any other boat I have owned or operated. It is more than a sound, it is a vibration-some minor shaking when coming up on plane slowly (2600-3000rpm). I have no vibration when trolling or operating at any constant speed or rpm. Could it be an out of balance prop?

Maybe you should try an aluminum prop just to see if the problem is still there. I'd be curious to know exactly what SS prop AND hub kit you have. By the way, it's not a bad idea to have a spare prop, so if you end up having to buy an aluminum prop rather than borrowing for testing purposes, don't feel bad.
All props are different.....including props that are supposed to be the same, right out of the box. But there are other potential factors such as engine mounting height, engine trim setting, specific hub kit in use, etc. etc.
I recently tested a new Merc F90 that I installed on an older 17ft. Montauk. We used a new Merc 21 pitch aluminum prop with a flotorq III hub. The engine was mounting quite high...second from highest hole.....we did not experience any strange vibration or cavitation upon takeoff. We always started with the engine trimmed all the in....and then trimmed out as needed once on plane.
Hope this helps.

Posted by RMN on 10/07/11 - 3:02 PM

I tried an aluminum prop (12 3/4-21-3RH-Al) and NO vibration coming up on plane at all. Even when the boat was kept in the range of 2600-3000 and not up on plane, there was NO vibration. However I did loose speed, coming down from approx 44-45pmph with the stainless steel prop (13 1/2-21-3RH-SS) to 38-39mph. Any thoughts or similar problems noted by anyone?