760 low end vibration

[Learnasyougo]

I just picked up a new RN with a stock 760 couch motor on rhass motor mounts. Leaving the harbor yesterday I noticed from maybe 2k-3500 rpm I was getting gnarly vibrations, literally my legs numb in the tray. Anything above that it seems to run and hook up fine, the vibrations disappear. Does anybody have an idea of what could be causing the abnormal vibrations?

Thanks

 

[Vumad]

Ryan's B1 with 701 vibrated a lot and so does my superjet. Sounds like yours may be much worse than ours but the Yamahas seem to make a lot of vibration in that RPM range. You might want to check your alignments though just to make sure you are not getting too much vibration. The mounts you chose could also be your culprit. Rhaas mounts are stronger than stock. I have recreational formula to soak up more vibration. If you went with the stronger stuff, more of your engine movement gets transferred to the hull.

 

[Henry Stephen]

And that vibration takes a toll on things like FA pods, throttle bracket(s). it's my Rhaas mounts.

 

[Vumad]

Just for the record. I am very pleased with my Rhaas mounts. I spoke to Rhaas before I purchased my mounts and he suggested I get the rec mounts over the heavy duty mounts to control the vibration, saying they were similar or only slightly more stiff than stock. Which seems to be true, but of a much much higher quality.

I don't want anyone to be misguided about Rhaas's parts or service. Both have been great. Unless you are planning on going huge, pancaking or stabbing the bottom of the lake, get the rec mounts. If in doubt, just ask @rhaas before you make your choice. I'm positive you will find him helpful and be pleased with the end result.

 

[Learnasyougo]

Awesome I appreciate the words of wisdom. I will check my alignment. I was talking to my buddy and he said I might have a chewed up or bent impeller or driveshaft. But looking at it and hand spinning, everything looks normal.