Discussion in 'General Downeast Dayboat Discussion' started by Ayonak, May 11, 2019.
Has anyone solved a vibration problem on a Mainship 34 Pilot at planing speeds?
Is your running gear all in good condition and your bottom clean?
Check all of the following;
Check the transmission coupler for looseness, made sure all nuts, bolts , set screws are tight.
Check the stuffing box , shaft seal, for any play also for loose set screws and fasteners.
Check the shaft / struts for and play around the cutlass bearings .
Make sure the prop nuts are tight and there is no movement or play in the prop with the shaft.
Check the prop for dings and bends in the blades.
Check the shaft for straightness , or dings . Most likely the shaft is fine.
And last check you engine motor mounts made sure they are snug .
Also check the rudder and post for looseness and any wiggle .
One or more of those things is causing your vibration I would say.
This is a boat I would like to buy, I do not own it yet. From the forums it appears this is a problem on many Mainship 34 Pilots. I have not seen a post from anyone who has actually fixed this problem telling what works. Most of the posts are opinions and not reports. If there exists a 90% fix for this I would like to buy the boat. I am wondering if a five bladed prop of smaller diameter would fix the vibration? Has anyone tried something like this?
Does the boat have prop pockets - that may be your source of vibration if vibration is persistent over a wide range of similar boats
Single or twin? Most 34 Pilots are single but if twin run up each by itself with the other in neutral and isolate to see if it's one side or the other or if it's both sides.
There's a possibility if it's a complaint across many of that model, some designs just don't like to run at certain RPM's without some vibration. You would need to avoid setting throttle there.
Other than internal engine trouble, you're looking at running gear. Start at the prop and work forward or start at the engine mounts and work backwards. On some boats vibration issues can be improved but not cured.
If it's a problem across the entire line, it is most likely improper propeller blade tip clearance. Another builder had this problem, and they would cavitate like crazy if you tried to get on plane too quickly.
Yes from what I saw on line about 34' Mainship Pilot it would appear to be prop tip clearance cavitation more so than vibration.
A smaller diameter prop would probably have a good effect on reducing vibration if it can still get the boat up on plane.
If I remember correctly, when the first Alura 30s were delivered, they had wheel vibrations.
The keel need re-shaping (aft end tapered) and the wheel was positioned a couple of inches farther from the keel, then problems went away.
Just not enough water was getting to the whole wheel correctly.
Prop pockets are a know culprit for many of these problems discussed. Doe the boat have them?
Thanks for the answers.
I do not know what prop pockets are but I doubt if these have them as the engine is a single with the prop behind a significant keel. It may be that the back of the keel could be tapered in front of the prop at some cost? I have been told the prop is a 25x28 with 2" shaft but have no way to confirm this as the boat is in the water and a 3 1/2 hour drive from me. Another post suggested these prop blade tips are 2" or a little more distance from the hull fiberglass above. a 22 inch or 23 inch should increase this clearance to 15% to 20% of the prop diameter. I understand the recommendation is 15% minimum clearance. To buy the prop, haul the boat and install a new prop is in the $3,000 to $4,000 range. This is certainly can be done but I do not want to buy the boat and then spent 4 boat bucks without knowing that this has actually worked for someone else. I am wondering if the prop diameter is reduced to increase blade tip clearance, should the pitch be increased? All this with a five blade prop replacing the existing four blade prop. Do you know anyone, owner or mechanic who has dealt with this vibration issue on a Mainship 34 Pilot? All help is welcome.
Is there any factory support left?
Marlow took over the Mainship Pilot line.
No factory support that I know of.
Did they took over the Hunter & Lurhs also (Gainesvile & St Aug)?
Worth a call to Marlo at least.
Your going to pull for surveys (we hope) and have a engine tech there also, you can get a better look at all and still decide on what you see.
If I offer on the boat it will stipulate a full survey and an engine inspection from a Yanmar mechanic plus a sea trial.
Hunter yes. I'm not sure what happened to Luhrs.