should props spin freely

[spurdog]

Ok well hit a log :smt021 in river before pulling boat and had a slight vibration. After pulling boat marina said the props look fine (by eye) and shaft looks straight. They think maybe the cutless bairings????? I did have a problem with the dripless not getting water from being clogged but i cleared that and all seemed fine. Any thoughts or price I should be looking at. If I change the cutless bearings on both shafts should I change the drippless also??????????

 

[nwocouple2006]

I don't have much experience with inboards as i just bought my first boat with them a month ago. If it were me i would pull the props and shafts and have them checked to see if they are true. you are going to have to pull them anyways to change the cutless bearings. The coupler can cause a vibration also if it is damaged. I would inspect the coupler very well and check your engine allignment. You could do that first since it would be the least expensive. I would think that it is very unlikely that that dripless would be damaged. Just inspect them and make sure the graphite surface on the puck is in good shape. I believe that can even be resurfaced easily if it were damaged.


Tim

 

[Alex F]

Yes, it's normal for props to spin freely.

Ok well hit a log :smt021 in river before pulling boat and had a slight vibration. After pulling boat marina said the props look fine (by eye) and shaft looks straight. .......

What you mean by eye, did they just look at them and said the props look straight?

 

[spurdog]

yes just by eye

 

[Alex F]

In this case I would disregard what they told you. There's no way for anyone to look at the prop and say it's not the cause of vibration.

I happen to heat a huge log on one long trip. After the impact I started feeling slight vibration that was hardly noticeble. When I got a chance, I dove to inspect the props and they looked perfect. I then did a test by loading each side while on plane and found that one side was clearly vibrating. I pulled the boat out and while knowing exactly that stbd side had vibration I saw (and marina staff saw the same) that the prop was in perfect shape. That was the preliminary visual conclusion until we did the bsic test, which is taking a long object pointing to the top blade off the rudder. Then, the prop was slowly turned to see if the distance of each blade is the same to the object. Similar basic test was done for the shaft, where a pointy object would be pointing right next to the center of the shaft and when the prop is turned you can see if the center is off or stays dead on. Based on test #1 we could see that one blade was slightly off. This was enough to create slightly noticeble vibration. Obviously, when I took the props to the shop one needed to be staightened and tuned. When it was reinstalled the vibration was gone.

From that experience I developed a pretty good feeling regarding vibration and basic steps to determine the cause.

Hope that all you have is slightly bent blade.

 

[cod]

Could never tell by eye. In my case, I did'nt have a vibration but had different readings on my guages for Load for each engine. Props looked fine and even tryed measuring blades from rigging a measuring stick to the strut. They measured the same. I had a mechanic check the engines and he suggested having the props reconditioned. I did that with a shop that uses "Prop Scan" and the loads were identical.

 

[geriksen]

In this case I would disregard what they told you. There's no way for anyone to look at the prop and say it's not the cause of vibration.

I happen to heat a huge log on one long trip. After the impact I started feeling slight vibration that was hardly noticeble. When I got a chance, I dove to inspect the props and they looked perfect. I then did a test by loading each side while on plane and found that one side was clearly vibrating. I pulled the boat out and while knowing exactly that stbd side had vibration I saw (and marina staff saw the same) that the prop was in perfect shape. That was the preliminary visual conclusion until we did the bsic test, which is taking a long object pointing to the top blade off the rudder. Then, the prop was slowly turned to see if the distance of each blade is the same to the object. Similar basic test was done for the shaft, where a pointy object would be pointing right next to the center of the shaft and when the prop is turned you can see if the center is off or stays dead on. Based on test #1 we could see that one blade was slightly off. This was enough to create slightly noticeble vibration. Obviously, when I took the props to the shop one needed to be staightened and tuned. When it was reinstalled the vibration was gone.

From that experience I developed a pretty good feeling regarding vibration and basic steps to determine the cause.

Hope that all you have is slightly bent blade.

This is pretty much exactly what we do.