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Is slow speed vibration normal

R

rustymich

Regular Contributor
Have twin inboards see a few p

Have twin inboards see a few people talking about vibration at slow speeds I also have vibration at slow speed starts around 6knots stops 8knots and above is there a problem here I can check out or is it normal?Also the book states taking shafts apart from trans when pulling from water I now most people at the marina Im at dont I want to no whats right no this matter Im learning alot here thanks all...
 
"could be any number of things

"could be any number of things, from a damaged prop, a shaft out of alignment, cutlass bearings worn, all the way up to bad engine mounts. I have flexible drive couplings on my shafts, & separate them when the boat is hauled in the fall.have a look at this site...http://www.yachtsurvey.com/Alignment2.htm..."
 
"Fastjeff Law of Inboards: Th

"Fastjeff Law of Inboards: They vibrate!

Why? Each prop blade sends a shock wave outwardly as it rotates. On inboards, the shock wave impacts the hull on its way "over the top". With outdrives, the shock wave is mainly dissipated in the water, with a bit of it impacting the cavitation plate, making them much smoother.

Note: The above does not rul out the following:

1. Misaligned prop shaft couplings

2. Loose or broken motor mounts, and

3. Rotted stringers that allow the motor to shift under load.

Jeff"
 
"Props perfect shape as are sh

"Props perfect shape as are shafts,cutlass bearings before launch didnt feel any play between shafts and bearing,theres no rotted stringers will recheck the shaft alignment not real bad just wondering if this is a problem and dont want one..."
 
Good idea to wait a few weeks

Good idea to wait a few weeks after launch before checking coupling alignment. Within 3 thousands is good.

Jeff
 
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