9.9 Engine Shakes/Hums new Boat - plus splashes water along the stern - need ideas!

[lordx]

Hey all, I just got a G3 Guide V14 fishing boat - and I paired it with my existing 2016 9.9 Mercury short shaft outboard engine.

The combo works well - however, I find that at speed, the boat HUMS audibly - and even worse - at slower trolling speeds, the engine SHAKES, and causes a rattling like sound throughout the boat and motor... not ideal for the fish....

Is there a rubber mat/pad or something that I could drape over the back of the boat where I mount the engine to help absorb the vibrations? Is there anything I can do to the engine itself to help reduce the shakes? It is a new engine that runs smoothly I feel... The engine is TIGHT on boat too.

Any ideas would be awesome!

 

[NHGuy]

Can you sandwich the clamps around some wood? And is your short shaft motor reaching below the hull?

 

[ondarvr]

​These Mercs tend to vibrate, part of the reason is the ultra lean jetting on the carb, slightly adjusting it can make it idle smoother and make it easier to dial in the exact RPM for trolling.

Drill out the brass cover over the low speed adjustment screw, then richen the mixture slightly.

 

[lordx]

​These Mercs tend to vibrate, part of the reason is the ultra lean jetting on the carb, slightly adjusting it can make it idle smoother and make it easier to dial in the exact RPM for trolling.

Drill out the brass cover over the low speed adjustment screw, then richen the mixture slightly.

You just gave me a mechanical heart attack. (drilling)

But this would not help the hull vibration at speed. Something the help absorb the vibrations would be nice.

 

[lordx]

Can you sandwich the clamps around some wood? And is your short shaft motor reaching below the hull?

I am pretty sure yes - because I brought it up to the beach, and the motor brushed the bottom before the front of the boat.

Also, just some regular plywood? Some hard rubber would seem like it would work better for vibrations... at least it seems that way in my head.

 

[Watermann]

How about some pics of your set up, be sure to show the stern with a shot of the motor on the transom taken at that level. Sounds like your Merc shorty is getting turbulent water above the bottom of the boat causing the symptoms you describe. You may need a long shaft motor with this particular hull if it has a 20" transom.