Yanmar 2GM20F Vibration

Jul 26, 2015
42
Watkins 29 Ft. Lauderdale
I recently purchased a Watkins 29 that had sat unused for a few years. I bought the boat on the West Coast of FliriFl and brought her back to Ft. Lauderdale in December.

The motor runs great. Starts right up. No smoke 0, no stink...runs great...except when I pour on the coals to get the boat up to hill speed....the engine starts a louder rumbli g noise and vibration increases as it gets up to WOT.

The prop is clean! The shaft is clean! It's a 2 blade prop.

Any thoughts as to cause? Cutlass bearing? Misalignment?
 
Dec 28, 2015
1,837
Laser, Hunter H30 Cherubini Tacoma
How do the motor mounts look? Does the exhaust change while it I'd doing this? Does it only do this while in gear?
 
Jul 26, 2015
42
Watkins 29 Ft. Lauderdale
Exhaust is perfect..no black smoke no oil residue on the water. Yes, it's in gear and moving along. Gps says I'm doing about 5.8 kts, approaching hull speed based on the increasing size of my wake as she settles in. Wish I had a true knot log to eliminate the effect of current.
 
Jul 7, 2004
8,402
Hunter 30T Cheney, KS
Could be your cutless bearing. Can you check it for play? Shaft could be bent. A dial gauge can test that.
 
Jul 26, 2015
42
Watkins 29 Ft. Lauderdale
I got in the water and gave the prop a good shake...it was solid! Now, I know that's not a valid test...but till I get her hauled, that's the best I have as of now! The vibration isn't there at mid power settings...only when it's wide open.

Almost like it's cavitating...but I don't think it is as RPM stays steady. It just rumbles and shakes and eventually gets up to or at least close to hull speed. Scared hell out of my wife the first time she was on the boat!

I'm wondering if it's normal with a two blade prop!
 

dLj

.
Mar 23, 2017
3,374
Belliure 41 Sailing back to the Chesapeake
If you look at the motor or transmission when it doing this, can you see either vibrating more than when it's it making noise? Almost sounds like a balance problem somewhere.

dj
 
  • Like
Likes: StargazerP303
Jul 26, 2015
42
Watkins 29 Ft. Lauderdale
That's my plan for later this week! To get it out in calm water, get it going full throttle and climb down in the lazarette to watch the transmission, and shaft log.

Do you think it could be a cylinder misfiring? Possible dirty injector? This boat sat unused for 2 or 3 years..before I got it

To better describe it, it's more of a deep rumbling vibration that only happens at full throttle.
 
Nov 6, 2006
9,885
Hunter 34 Mandeville Louisiana
Look carefully at the motor mounts.. If there is very little clearance between the top steel plate of the mount and the bottom plate of the mount, they may be making contact when at high power settings. You can sorta test for bad mounts by shaking the engine by hand .. if you hear a knocking noise, you probably have a bad mount.. grab the heat exchanger and shake fore/aft first then port/starboard.. If there is no knocking and the plate gaps on all mounts, fore and aft of each mount, then your shaft alignment is probably the culprit..
In the picture, the gap I am talking about is the gap between the top plate after the bend where it gets close to the bottom plate.. Over the years, the rubber relaxes a bit and the mounts can sag.. Good luck..
New Engine Mount.jpg
 
Jul 26, 2015
42
Watkins 29 Ft. Lauderdale
That would make sense and explain why it's only noticeable at full throttle under load!
Going to the boat today to check that out!


Thanks.
 
Jul 26, 2015
42
Watkins 29 Ft. Lauderdale
Thats my first thought as well....I've never I owned a boat with a two bladed prop before. My first guess is that under very heavy load, the prop is cavitating.
 
Jan 19, 2010
1,169
Catalina 34 Casco Bay
Was there any sign of pitting on the prop when inspected? If NOT, this may be more a case of ventilation than cavitation....
 
Jan 22, 2008
112
Hunter 36_1980 Bass River, NJ
Just my 2 cents, I have a 2QM20F 1980. Had a two blade when I bought her. About 10 Years ago had new cutless bearing and shaft installed. Always had vibration under my feet at higher throttle. About 5 years ago, looking for more thrust, switched to a Campbell 3 blade sailor prop. Thrust increased, achieved Spec RPM (surprised) and
first thing I noticed was the Vibration under my feet went away. Kloudie 1 made the good suggestion to inspect your motor mounts. Easy Check, do it first.
Hope this helps,
 
  • Like
Likes: StargazerP303

Mikem

.
Dec 20, 2009
820
Hunter 466 Bremerton
My son had the same engine on his previous H306. Same vibration symptoms. Three of four motor mounts were broken...the rubber portion that is. Replaced them and everything was fine.
 

MitchM

.
Jan 20, 2005
1,011
Nauticat 321 pilothouse 32 Erie PA
have you checked your coupler betw prop shaft and gear box for proper faceout ? do you get readings different from yan specs ?
 
Oct 14, 2017
89
HUnter 306 Aruba
I have vibration when the engine is not in gear, brand new yanmar mounts put in place 3 years ago. still vibrates when in gear.
working on a solution in the coming days. keep me posted if you find a solution and i will do the same. Good Luck.
 
Oct 22, 2014
352
Pearson P303 #221 RockPort Maine
I recently purchased a Watkins 29 that had sat unused for a few years. I bought the boat on the West Coast of FliriFl and brought her back to Ft. Lauderdale in December.

The motor runs great. Starts right up. No smoke 0, no stink...runs great...except when I pour on the coals to get the boat up to hill speed....the engine starts a louder rumbli g noise and vibration increases as it gets up to WOT.

The prop is clean! The shaft is clean! It's a 2 blade prop.

Any thoughts as to cause? Cutlass bearing? Misalignment?
I installed one of these, after spending enough money trying to get results. Very easy to install yourself!
R&D Marine, Flexible Couplings