Mainship Pilot 34 Vibration Problem

I am interested in purchasing a 2001 Mainship Pilot 34 with a single Yanmar 6LYA-STE 350HP turbo diesel engine. Today, while doing the sea trial I noticed an in and out vibration that began around 2200 RPM's and worsened when the RPM's were increased. The engine maxed out WOT at 3550 RPM's. The owner (the 2nd owner and has had the boat for 3 years) said he had the prop checked 3 months ago, when it was gauged, balanced and repainted. The shaft is true and there was no wear on the cutlass bearing. And yes, I have heard rumors this is a known problem with the Pilot 34!
When the boat was short hauled for survey, the prop (clean w/o any damage) was ID'd as a 25x28 w/4 blades. The clearance from the prop tips to the tunnel was slightly over 2" and there was some paint wearing in the tunnel over the props. My thought is the prop is over sized, but I would welcome any feedback from anyone who may have knowledge of this issue . . . Better yet, a solution would be MOST WELCOME!

Welcome to the forum. There are others more familiar with the specific history of this problem, as it was more or less pronounced from year to year, so I will answer in general

The concept of reduced tip clearance is to increase thrust and speed, sometimes at the cost of added vibration. The standard "rule of thumb" for tip clearance is minimum 15% of prop diameter.

What you describe with the missing paint is called "tunnel burn," and is typically considered evidence of insufficient tip clearance.

On some Mainship models there was a factory warranty fix to correct this issue. I believe it was a propeller change to 5 blade with less diameter.

This is about the Pilot 30, but the same issue is well known in some 34 models:

BoatUS - Boat Reviews - Mainship Pilot™ 30

This is a thread about same in a P30

http://www.trawlerforum.com/forums/s3/vibration-high-rpm-35073.html

I expect some P34 Peeps to chime in, but this is a start.

If the P34 fits your Bill for what you are looking for in a boat, if it was my decision I would not let this be a deal breaker as its "fixable." The Pilot 34 is a great value and IMHO for what its designed to do a great boat.

Keuka said:

And yes, I have heard rumors this is a known problem with the Pilot 34!
The clearance from the prop tips to the tunnel was slightly over 2" and there was some paint wearing in the tunnel over the props. My thought is the prop is over sized,

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My 2003 Pilot 34 has a little of this problem. It is unnoticeable if the bottom is clean but worsens with a dirty bottom.

I would check the normal prop vibration issues:

1. Prop trueness- your surveyor should have held a straight edge in place and rotated the prop to see any lack of true.
2. Prop shaft straight- rotate with a dial indicator at several points along the shaft
3. Prop seated properly on taper- would have to pull prop to do
4. Coupling square to shaft- check as part of 5. Open the coupling and rotate tanny and prop shaft with a dial indicator on the faces.
5. Engine alignment

One or more of these could be causing your vibration. If all are good then this boat may be more prone to the hydraulic/dynamic vibration problem. Some report success with fairing deadwood. It didn't make any difference on mine.

Good luck.

David

Might worn engine mounts also be an issue?

I have dealt with mystery vibration problems that proved to be bent coupling faces, especially on the transmission side after Having work done off the vessel.
The coupling half is often the lowest point on a drop output transmission, so consequently hits the ground first when mishandled.
I would inspect the entire power train very carefully before investing in a new prop.

How do I access the fuel tank in the Mainship 34 in order to polish the fuel?

34' Mainship single diesel - vibration problem

I have a 34' Mainship with single Yanmar 370hp engine. Vibrates badly from about 2200 rpm to wide open 3300 rpms. Has anyone put a 5 blade prop on to fix this? If so, what is shaft size and prop size. Thanks

I have a Pilot 34 with same prop (newly replaced in 2022, same as original) and have the same vibration issue. This new prop was dynamically balanced. I had a 24" (same pitch) prop in for 2nd 1/2 of the season in 2021 and found I still had significant vibration at high RPM. I have been attributing the vibration to cavitation at high RPM.

Greetings,
Welcome aboard. As you're aware unwanted vibration IS a known problem with some Mainship Pilots. We were interested on one a while back and the owner was totally upfront about the vibration. He had attempted to ameliorate the problem by switching to a 5 blade prop. Evidently the vibration DID lessen somewhat but was still there. I know this doesn't help much but...

A 25” diameter prop should have, at a minimum, 2.5” tip clearance (10%). But 15% is better, so it really should be 3.75”. That is where I would start looking for the vibration. That is easy to do. Then get into the hard stuff if that doesn’t fix it. As said these boats apparently have this as a known issue.

Pilot 34 vibration issues
I think there may be a simple solution to the vibration issues
However in order to clarify and narrow down the source
Please respond the the following survey

1 model year
2 single or twin
3 bow thruster
4 bow and stern thrusters
5 location of boat
6 bottom paint used
7 shaft zinc type

Please answer all in order
I hope it will help to confirm my theory of vibration cause?

Greetings,
Mr. o. VERY interested in your theory. Personally I can't see where anything other than zinc type would have any effect. As I mentioned, unwanted vibration is a known issue with some MS's and from what little I understand, it seems to be individual boat dependent. One would think if rectification was simple it would have been addressed and common knowledge.

See answer below:

oak said:

Pilot 34 vibration issues
I think there may be a simple solution to the vibration issues
However in order to clarify and narrow down the source
Please respond the the following survey

1 model year 2003
2 single or twin single
3 bow thruster yes
4 bow and stern thrusters no
5 location of boat NC and Ct
6 bottom paint used Pettit
7 shaft zinc type Collar on shaft and circular one on rudder. Made no difference in vibration whether rudder zinc was new or completely gone.

Faired the deadwood, but no difference. The only thing that made any difference was bottom condition. A clean bottom produced no vibration. Once it got a little dirty, vibration would kick in but never below 2,900 rpm.

Please answer all in order
I hope it will help to confirm my theory of vibration cause?View attachment 134819View attachment 134819

Click to expand...

RT Firefly said:

Greetings,
Mr. o. VERY interested in your theory. Personally I can't see where anything other than zinc type would have any effect. As I mentioned, unwanted vibration is a known issue with some MS's and from what little I understand, it seems to be individual boat dependent. One would think if rectification was simple it would have been addressed and common knowledge.

Click to expand...

I understand it a known issue and greatly discussed. I have been part of that discussion. I have also spent more than 15k trying to solve the issues. I replaced the cutlass bearing, removed prop and shaft tuned balanced and finished with prop speed. I also removed the rudder and had it checked
I replaced the motor mounts and had the engine re aligned. I replaced all zincs and had bottom painted.
All work was done by a certified diesel mechanic who I requested to fix anything that may be related to vibration issues. After all of this the vibration returned several months later.
On my last haul out to paint bottom and wax I made an observation that may solve the issue.
The survey would help verify
So not sure why anyone with this issue would not answer the simple survey??

.

Oak, your list of interventions performed to Miri is beyond comprehensive, which makes your "observation that may solve the issue" remark seem calculated to drag out the suspense. Would disclosing your observation to those of us who are sufficiently concerned to be reading along somehow pollute the results of your survey?

I am unable to respond to all your data points, however I experienced this annoying vibration in an immaculate, well-sorted MS 30' Pilot II, 315 hp Yanmar w/ 4-bladed prop in tunnel. My strong suspicion then and continues to be the motor mounts, but I was never able to test that all the way to proof, so I am following this with interest.

I agree that more disclosure by the OP might net better discussion. It's hard to comment on something as broad as "vibration". All boats have some, how do you know what's normal vs. a fixable issue? Sounds like yours was fixed for a few months then returned? During my sea trial a few years back, some noise and vibration was noted at full throttle and full port rudder. It was first thought to be an issue with the newly added zincs but they were re-checked and everything looked fine. The conclusion was that it was normal turbulence of the prop in the tunnel under those conditions.

backinblue said:

I agree that more disclosure by the OP might net better discussion. It's hard to comment on something as broad as "vibration". All boats have some, how do you know what's normal vs. a fixable issue? Sounds like yours was fixed for a few months then returned? During my sea trial a few years back, some noise and vibration was noted at full throttle and full port rudder. It was first thought to be an issue with the newly added zincs but they were re-checked and everything looked fine. The conclusion was that it was normal turbulence of the prop in the tunnel under those conditions.

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Correction. These comments were directed at OAK, not the OP. Seems as though he will not reveal his secrets anyway.

backinblue said:

Correction. These comments were directed at OAK, not the OP. Seems as though he will not reveal his secrets anyway.

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As there have been only one response to my survey
And it doesn’t conform to my theory
I will clarify what I found
After doing all the work I indicated to alleviate the vibration and then had it return I was baffled to say the least
Well on my last haul out I discovered that the stern thruster shroudes were loose and installed with acorn nuts and two were actually missing. The shrouds were free to vibrate against the thruster tunnel. I replaced all the fasteners with aviation nuts and loctite.
So far no vibration at any rpm.
I was to see if others had a stern thruster and the same issues.
However the only response was a MS 34 with out a stern thruster. So seems to have solved my problem so far, but maybe not the universal solution I was hoping for.

oak said:

As there have been only one response to my survey
And it doesn’t conform to my theory
I will clarify what I found
After doing all the work I indicated to alleviate the vibration and then had it return I was baffled to say the least
Well on my last haul out I discovered that the stern thruster shroudes were loose and installed with acorn nuts and two were actually missing. The shrouds were free to vibrate against the thruster tunnel. I replaced all the fasteners with aviation nuts and loctite.
So far no vibration at any rpm.
I was to see if others had a stern thruster and the same issues.
However the only response was a MS 34 with out a stern thruster. So seems to have solved my problem so far, but maybe not the universal solution I was hoping for.

Click to expand...

Thanks for the revelation. For what it's worth, I have bow & stern thrusters but I removed the shrouds from my stern thruster a couple years ago. Not because of vibration, but they do detract somewhat from the sideways thrust as a % of the thrust is directed downward. My theroy is that the stern thruster was sufficiently submerged not to need them. I think the shrouds are installed by default but at least on my boat the bow and stern thurster are at about the same depth. Unless yours is just barley beneath the surface you might want to try running your w/o them. Mine seems fine. They can always be easily re-attached if wanted by the next owner. So the result in my mind is that I probably get a little more thrust and it's a little less apparatus attached underwater to the stern of my boat so maybe tiny bit less drag or potential for vibration or other issues.

I have owned a 2007 34 Pilot since 2020. It is located on Lake Erie with a bow thruster, no stearn thruster. It is probably ready for a new coat of ablative paint. We never had vibration untill late July of 2022. Vibration started at about 2200 rpm. When we pulled the boat for winter storage, the bottom was much dirtier than usual, mostly on the side facing the setting sun. In previous years, we had a large boat next to us blocking the sun. Last year a pontoon boat replaced the larger boat, much more sun. Hoping the dirty bottom was the culprit. Will report back later. Nick

I had the same experience with my 2003 Pilot 34. A dirty bottom led to vibration and a clean bottom did not vibrate. The clean bottom picked up a few kts at wot.

Something related to more prop slip with a dirty bottom, I suspect.

David

Question:
Did any Trim Tabs adjustment have any effect on the intensity of vibration on your boats?

It seems to be a feature of the MS 34s

NIKBRUSH said:

I have owned a 2007 34 Pilot since 2020. It is located on Lake Erie with a bow thruster, no stearn thruster. It is probably ready for a new coat of ablative paint. We never had vibration untill late July of 2022. Vibration started at about 2200 rpm. When we pulled the boat for winter storage, the bottom was much dirtier than usual, mostly on the side facing the setting sun. In previous years, we had a large boat next to us blocking the sun. Last year a pontoon boat replaced the larger boat, much more sun. Hoping the dirty bottom was the culprit. Will report back later. Nick

Click to expand...

Take a look at your cutless bearing and shaft alignment. That seems to be an issue on some Pilots.

backinblue said:

Take a look at your cutless bearing and shaft alignment. That seems to be an issue on some Pilots.

Click to expand...

I just have heard from a fellow 30 Pilot II owner who has been working to resolve a nuisance amount of noise, vibration, and harshness (NVH), and he has discovered upon removal of the strut that it was mounted to the hull with 5200 or the like used as filler rather than having its whole mounting surface solidly mounted to the hull. He is a professional in the field and considers this a factory error. He has not yet reported the efficacy of his fix.

I experienced a notable vibration in my 30 P II in the 2000 RPM range but once over the hump, it was not present. Found out that one of the five blades of my 22X24 prop was almost an inch out of true. Reduced pitch to 22 to regain some lost WOT RPM and trued up the prop, and a mechanic riding the boat for another reason noted the smoothness of the ride throughout the RPM range. Apparently my strut got mounted correctly.

Thanks Rich. When the yard replaced my cutless this spring they could not get the shaft aligned so they removed the skeg/strut and made a molded "shim" between the skeg and the hull to fix it. Probably also a factory error or maybe from hitting something, I don't know for certain. Regardless, I believe it is nor correct and I also had the prop trued up the same time. Seems smotther and quieter but that could also just be my imagination because I know it better than it was.

2005 Pilot 34 Experience

Just to add to the confusion, I just picked up my (new to me) Mainship Pilot 34 with a single Yanmar 370hp engine on Lake Oneida and am heading east on the Erie Canal as I write this.

When I had the boat surveyed last Fall (I could not be present) the surveyor noted severe vibration above 2200 rpm that got progressively worse as rpm climbed. He noted this as being so severe that he felt the engine might be loose on it's mountings (it is not). In his survey report he indicated that this needed to be rectified immediately.

I fretted over this all winter in Maine awaiting my planned pickup of the vessel in the Spring. I read all the posts and threads with increasing trepidation in that no one seemed to have found a consistent solution to the vibration and harshness issue.

So, at the first opportunity upon picking up the boat this week, I opened the throttle progressively to WOT and thankfully did not detect anything I would consider abnormal other than a lot of engine noise and relatively normal engine vibration. There was no disturbing shaking, cavitation, or other objectionable behavior.

What could possibly have changed since the sea trial by the surveyor in September and my first running this week? The boat was stored indoors for the winter and the only thing I did was change the zincs (aha!?) and paint the bottom. So was the bottom dirty last Fall? Was the shaft zinc at fault? I painted the bottom this Spring and replaced all the zincs. That's it. So I will be interested to see if vibration creeps in as time goes by and the zinc wears or the bottom becomes fouled.

One other thing to contribute to the prop size, clearance, and condition discussions. The prop on my boat is 25 inches in diameter but I don't know the pitch. I did check to make sure that it rotated true on the leading and after edges and it was within a 16th to 8th of an inch or so. One thing I did note though was that the clearance between the prop tips and tunnel was more like five inches, not the smaller values mentioned elsewhere. That seems ample given the prop diameter and exceeds the oft stated 15% of diameter rule.

So there are some useless data points to add to the conversation. I did not notice vibration at speed when I personally sea trialed the boat last August when contemplating its purchase. The surveyor then said the boat was shaking itself to pieces in September. It seems to be fine now. Who knows???

I will give feedback as time goes by if I begin to notice any change. For now, I can run up to 16.5 knots with the 370hp single Yanmar with no issues. Fingers crossed.

Doug

My guess would be that there was a dislodged or partial shaft zinc that was causing an imbalance, line or other debris wrapped on the prop, or sea growth. Few problems resolve themselves, so congratulations on winning the lottery[emoji106][emoji3]

This is a follow up to my post no. 20. The boat went in the water on 6/8/23. The bottom had been power washed prior to winter storage. This year, no vibration at any speed. I ran it about 6 hours. Thanks, DavidM, perhaps
a dirty bottom does causes prop slip and vibration.

The boat is a soft top with the original propeller 25 x 28 Long Tip. I measured the distance from the tip of propeller to the top of the tunnel at 5". The ablative paint in the tunnel was fine (no tunnel burn).

Nick