Excessive Vibration MS Pilot 34

Our 2007 MS Pilot 34 suddenly developed a lot of vibration above 2000 RPM and got worse at 3000 RPM where the whole boat is vibrating. Took it to t h e marina where they hauled it and checked the running gear. Could not find excessive play in the cutlass bearing, the engine and trans seems to be okay, took off the swim ladder, and prop shaft line cutter and still vibrates. It seems to be downhill of the shaft log. They want to take the prop in but we never hit anything and it was checked and found to be in spec when we bought the boat. Will have the marina replace the cutlass bearing tomorrow. They are going thru the process of elimination. What type of shaft log do we have? 2 pieces? Any o n e have any ideas? Thanks for any recommendations!!

The Pilot 34 has a well known and discussed (on this forum) problem with prop cavitation or similar cause. On my boat it slowly increases after a bottom cleaning and is back to normal after a good cleaning.


So the first thing to ask is do you do routine bottom cleanings and did this problem occur after the boat sat for a month or two in the water (salt of course) where fouling could have bloomed suddenly.

If this is not the case then look at the common causes of prop vibration:

0. Run the engine up in neutral. Does the engine shake. Could be torsion damper is failing.

1. Tighten the coupler bolts, then put a dial indicator on your prop shaft (inside the boat) and look for run out. Should be less than .005".

2. With the boat hanging in the Travellift slings, hold a pointer at the tip of the prop and turn it. You should see very little, ie 1/16" or less variation.

3. Check to see that the prop nuts are tight, although #2 is a pretty good indication that they are and that the prop is seated on its taper.

4. Put a dial indicator where the zinc goes on the prop shaft and check for runout there.

5. Finally if all of the above checks out, pull the prop and send it to a prop shop for truing.

David

Also, check the condition of the engine mounts. They could be the cause even if they look ok. Engine to shaft alignment causes some weird vibrations that seem to come from nowhere. Do an engine alignment in the water.

ben2go said:

Also, check the condition of the engine mounts. They could be the cause even if they look ok. Engine to shaft alignment causes some weird vibrations that seem to come from nowhere. Do an engine alignment in the water.

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Check your shaft zinc. A worn zinc can cause the shaft to be unbalanced and vibrate especially at high rpm.

Wanted to share all what we did and the outcome. At first haul out, found that the shoe was a little loose and found some scraped paint on the shoe where the bottom of the rudder rubbed on the shoe when turning the rudder. They tightened the bolts on the shoe and raised the rudder at the rudder post so the rudder would clear the shoe. That didn't fix the problem. Hauled it again to change the cutlass bearing. Found the hose supplying cooling water to the cutlass bearing needed replacement, replaced the drip seal on the shaft log since it was all apart, found the bushing/ cutlass bearing on the shoe where the bottom rudder pin attaches had become elongated so was replaced, added a shim between shoe and rudder pin, balanced and tuned the prop, and repacked the rudder post. They supposedly aligned the engine and checked that the shaft was in spec but we were not present for this.

Went for the sea trial and reached 3400 RPM (if tach is accurate) at WOT. Was only out for 10 minutes and the vibration and loud growling noise were gone. Thought all is well but on our 5 mile trip back to the marina, at anything above 2000 -2200 RPM, the engine noise seemed louder than usual, and seemed to be centered above the cutlass bearing and shaft. We even commented that if we cruised at speed for any length of time that we would need ear plugs. Only had the boat out a couple of times before this happened and didn't notice excessive engine or running gear noise.

Any ideas why it is so much louder after we had all of this work done? Is it normal noise due to break in of a new cutlass bearing, or do they need to recheck the engine alignment? They did not check the torsion damper. Again, no vibration, but just pretty loud when running. Thanks to all!!

Maybe it was not so much engine as cavitation noise at that speed. I certainly experience something maybe similar (though maybe not exact) as you do at the 1800-2500 range as I am passing through on the way to getting over the hump at 2700 RPM. I seldom run the boat at less than 2800 except when warming up or cooling down in the channel in and out of my bayou when I run at 1400 or so.

So vibration is all gone, right. To be sure:

Look at the prop shaft at speed. It should run true with very little wobbling.

Put a cup of coffee, coke or whatever on the aft transmission. You should see a slight ripple across the top but nothing major.

If the above is ok, then yes you could be just hearing cavitation. Is your bottom clean? Should be if you had it out of the water for all of this work recently.

On my Pilot 34 if the bottom was a little dirty the noise would start in the mid 2,000s and increase all the way up to wot. Others have reported cavitation noise whether the bottom were clean or not. So it does sound like you solved the vibration but you are now left with cavitation. And yes a long cruise at 2,800 rpm could require ear plugs on mine.

The only solution that I have a fair confidence would work is switching to a five blade prop. You have probably spent as much already as a 5 blade prop would cost trying to solve this problem. The one downside is 5 blades is less efficient so you might lose a little speed with one. Talk to a good prop shop and see what they say.


David

I have been through these same vibration issues and have written about it in several posts. However here is my story and what I believe to be my solution.
I purchased The boat in 2016 sea trialed and it surveyed perfect. After about 9 months the vibration/cavitation began. The vibration began around 2600 rpm and progressively got more noticeable as I increased rpm’s. I then hauled the boat and proceeded to fix anything and everything that could possibly be the issue. I had the prop, rudder and shaft removed and scanned and balanced. I replaced the cutlass bearing and shaft drip less shaft seal. I changed the motor mounts and realigned the engine. The bottom was painted and the running gear was painted with a hard paint. ( by the way a new cutlass bearing should make no noise and the shaft should turn easily). I then launched and the boat ran perfectly at all speeds. She ran perfectly for about 10 months and then unbelievabley it returned. I then hauled again, but this time I just painted the bottom and replaced the zincs. After launching I took a cruise to the Keys. The boat ran perfectly at all speeds. So I now think that I probably spent a lot of money unnecessarily at first and that the solution is the the boat needs a clean bottom and intact shaft zinc. I think that a worn shaft zinc causes an imbalance in the shaft as the shaft cantilever is a the outer limit of what is required (the distance of the unsupported length of the shaft to the prop should not be more than 21/2 x the shaft diameter or 5” in my case.)

5” of shaft between the prop and the strut does seem like a lot. Can you shorten the shaft to reduce that distance?

One change that I did make was replacing my chain/line anchor rode with all chain. This weighs 190 lbs. Can't see how this makes any difference.

5” is the maximum that the shaft cantilever should be. When the shaft zinc is worn it may cause the shaft to be out of balance.
A clean bottom is also a must. In south Florida where I am a diver is necessary at least once a month.
Also the yanmar 375hp is noisy at high rpm but this is not vibration. As far as changing to a 5 blade prop the boat ran without vibration for months without vibration so I do not think the prop is an issue. My prop is 25R28

While probably not the answer to your issue, but I was experiencing a slight vibration increase on my Port engine. I popped down into the engine room under way and saw quite a bit of water dripping out of the stuffing box (I use Gore shaft packing) where there should be none or just a drip once in awhile. Next day I tightened the packing gland down a bit and the water and vibration stopped. Maybe just 3/4 turn on each nut.

Regarding the issue of vibration. I have a 2007 pilot with a single 370 yanmar. If you are experiencing ongoing vibration, I suggest that you check the alternator belt. When the belt has excessive slack it can slap against the protective shroud. This can create quite a racket and vibration noise that travels throughout the entire boat.
If this does solve your issue please let the forum know. I did this and it did solve the problem. However I did it in conjunction with having bottom painted and new zincs. So if you are in the water and experiencing vibration check the Belt tension.

Sorry for the delayed response, but to close this post, ended up with new cutlass bearing, New cooling hose for dripless shaft, replaced shim in between shoe and rudder pin, repacked top of rudder post which was leaking, and balanced prop. After a couple of hundred miles, had a different yard check and align the shaft coupling and motor mounts which were off, where they FOUND THE BELT TENSIONER WAS LOOSE where the alt belt could have easily slung off so THANKS FOR THAT SUGGESTION. The vibration is gone but after about 2400 RPM it starts getting pretty loud. If we run fast thinking of getting earplugs. Thanks to all who replied!