Heard a whine the other day while motoring into the harbor. After investigation this is what I found: Whine is do to prop shaft wobble. I observed this wobble from inside the boat between the coupling and the dripless shaft seal. I also have vibration. Starts at around 1400-1500 rpm in forward gear. Whine/vibration quiets (not completely) down when I go to higher rpm. Motor mounts look ok. No whine/vibration in neutral or reverse at any rpm. I do have a feathering Kiwi prop. What do you think is causing prop shaft to wobble? Thanks for the inputs.
Prop shaft wobble
- Thread starter Pat T
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Additionally, I did jump in to take a quick look. I could not find anything obvious. I was hoping to find something wrapped around the prop - no such luck.
Thanks for the input Doug. I would think that if I had a bend prop blade ( they are composite) then it would also wobble in reverse, but it doesn't. The same argument could be made for a worn cutlass bearing? All is smooth in reverse though.
FYI, I did replace the cutlass in the spring.
FYI, I did replace the cutlass in the spring.
Some of the vibration could be coming as harmonic vibration. The engine will vibrate at all speeds but if the vibration of the engine and the shaft and the prop become synchronous at the 1400-1500 rpm range the vibration will become more powerful. Some of the stays on my boat vibrate in sync with the engine and some speeds and a very small throttle change stops it.
I have a newly installed Yanmar 2YM15 and have noticed an engine vibration at that very same rpm 1400 to 1500. We now have just 25 hours on the engine and it seems to have diminished slightly. It is not particularly troublesome, but I notice that the PSS seal sprays a slight amount of water just at that rpm range when the transmission is in drive. Anything higher or lower is smooth and there is no water leakage.
We looked for shaft wobble and find none. We run the engine in neutral at that rpm and find the vibration to persist and we can see the vibration on the mounts, so it appears that vibration at that engine speed is a symptom of the engine, not the shaft or prop.
How old and what make is your engine and has this always been an issue?
We looked for shaft wobble and find none. We run the engine in neutral at that rpm and find the vibration to persist and we can see the vibration on the mounts, so it appears that vibration at that engine speed is a symptom of the engine, not the shaft or prop.
How old and what make is your engine and has this always been an issue?
My boat is a 95 with the original engine. I have had the boat 7 or 8 years. This problem just showed up. I am suspecting the prop. Each blade can be individually pitch adjusted for forward but not for reverse. The fact that I only have the problem in forward and not reverse leads me to believe that one of more of the blades is no longer pitched correctly for the forward position.
Tomorrow I am planning to don scuba gear and pull the prop and put my old 3 blade fixed back on.
Tomorrow I am planning to don scuba gear and pull the prop and put my old 3 blade fixed back on.
If you are otherwise satisfied with the Kiwi Prop's performance, why not simply reset the blade's pitch? It is pretty simple to do. Here is a link to the instructions for this:
http://www.kiwiprop.us/installation.html
BTW- if you are going to remove the Kiwi Prop, you will need a prop puller.
http://www.kiwiprop.us/installation.html
BTW- if you are going to remove the Kiwi Prop, you will need a prop puller.
Yes, setting the pitch is easy. But finding the one or two blades that are out of pitch (while underwater) is the tough part.
I have the puller, a 3 jaw, that I used to remove my original prop. Hope it works on the Kiwi !
I have the puller, a 3 jaw, that I used to remove my original prop. Hope it works on the Kiwi !
Yes Ross but I have a 28 mile journey to the boat yard to per her away. Not always able to sail the full amount and I will have to do some motoring. If I have to I could motor at low rpm's but if I can fix the problem then the journey will be a lot easier/quicker.
Just remembered I should have closed this thread out a while ago.
I was able to get the Kiwi prop off easily with a couple of gentle raps. The gear puller would never have worked as there is nothing to grab on the forward side of the Kiwi - it is rounded. Put the old fixed blade on and still had some wobble. Then I decided to check the motor mounts and found one loose. Should have made that my first check! But I also found one blade on the KIWI to be off. Not sure if this caused the vibration that maybe loosened up the motor mount. I don't think I'll ever find out.
I was able to get the Kiwi prop off easily with a couple of gentle raps. The gear puller would never have worked as there is nothing to grab on the forward side of the Kiwi - it is rounded. Put the old fixed blade on and still had some wobble. Then I decided to check the motor mounts and found one loose. Should have made that my first check! But I also found one blade on the KIWI to be off. Not sure if this caused the vibration that maybe loosened up the motor mount. I don't think I'll ever find out.
A loose prop may have been part of your problem. No prop should come off with a couple of gentle raps, if it does it was never properly installed.
Oooh. That screw wasn't lapped. Don't take a lot to throw one "out of round"..
Years ago, just for the meanness of it, (He was a good friend, that's who you do the really mean stuff too), I reached up and duct taped a couple of quarters to the end of one blade on a ceiling fan in his house, and it about tore the damn fan out of the ceiling. When I used to drink, that was the extent of my physics experimentation..
Cool lesson though..
Years ago, just for the meanness of it, (He was a good friend, that's who you do the really mean stuff too), I reached up and duct taped a couple of quarters to the end of one blade on a ceiling fan in his house, and it about tore the damn fan out of the ceiling. When I used to drink, that was the extent of my physics experimentation..
Cool lesson though..
The kiwi is only torqued on with 10 ft lbs. I use a collar zinc ahead of mine. When I pull the prop I loosen the screws on the zinc and let it bear against the hub of the kiwi. Use my 3 legged puller against the zinc. However the kiwi usually pops free with very little torque on the puller.
Do the blade adjustment on the bench.
Do the blade adjustment on the bench.
Yes, only 10 ft. lbs of torque to install. I bought a torque wrench just to install this prop. They caution not to over tighten. Additionally they recommend greasing all surfaces of which I did. I think following their directions and the fact that this prop was on for less than 1 whole season was the reason why the prop came off easily. Good to hear this is the case from someone else.
I like the idea of the collar zinc. I will have to look for one for use next year. Thanks again all for the comments.
I like the idea of the collar zinc. I will have to look for one for use next year. Thanks again all for the comments.
This is interesting in that propellor professionals will tell you that putting anything on the shaft taper or interior surfaces of the prop bore is a no-no. The reason being that the taper and bore are designed to mate perfectly and a layer of grease (or whatever) can prevent that from happening. Additionally, props are not supposed to come off easily. You don't want that prop to be able to slide up and down the shaft in the event the nut loosens up or wasn't torqued properly in the first place.
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