Reply
 
Thread Tools Search this Thread Display Modes
 
Old 11-28-2022, 12:28 PM   #21
Senior Member
 
Cold Duck's Avatar
 
City: Discovery Bay
Vessel Name: Cold Duck
Vessel Model: MS 350 Trawler, 1997
Join Date: Jul 2022
Posts: 196
Quote:
Originally Posted by Cartouche View Post
The 390 has no tunnel underneath it is flat you must have been testing a 30 or 34
Agreed, single engine 350/390s have a keel.
Cold Duck is offline   Reply With Quote
Old 12-02-2022, 06:49 PM   #22
Veteran Member
 
City: Knoxville TN
Vessel Model: Mainship 390
Join Date: Feb 2008
Posts: 46
Thanks to everyone for all the excellent input.
A quick update on the situation: The sale is pending and contingent upon the vibration issue being corrected. The seller is working the problem now. The boat was hauled (again) and is now on the hard. So far we've found that there was an issue with one of the prop blades - that is being corrected. Also waiting on a new shaft to be delivered and installed.

Hoping this improves it. We'll do another sea trial after the shaft is installed. Gonna be cold out there.
Souvenir is offline   Reply With Quote
Old 12-03-2022, 12:31 PM   #23
Guru
 
Steve DAntonio's Avatar


 
City: Deltaville
Join Date: Dec 2015
Posts: 920
Anxious to know the exact cause, keep us posted.
__________________
Steve D'Antonio Marine Consulting, Inc.
https://www.stevedmarineconsulting.com
Steve DAntonio is offline   Reply With Quote
Old 12-04-2022, 06:24 AM   #24
Senior Member
 
Derek's Avatar
 
City: Fayetteville
Vessel Name: Donna Mae
Vessel Model: 2005 Mainship 430
Join Date: Nov 2016
Posts: 121
Quote:
Originally Posted by Souvenir View Post
Wondering if anyone else has seen this issue.



We had the marine survey yesterday on a 2000 MainShip 390, single Cat 3116 with around 1950 hours on it.



Last week the prop was serviced, the shaft alignment was checked, new bearings and dripless shaft seal.



During the survey, we had very smooth running up until around 1900 RPM. Significant vibration started at that point, then smoothed out again around 2400 RPM. WOT was around 2800 I think.



My first guess is that the prop was not seated properly. Next likely problem might be shaft alignment with transmission. Surveyor verified the rudder was in good shape before boat was launched. No obvious engine mount issues (per surveyor).



Otherwise, the boat is in very good shape. Hate to have this derail the purchase.



Any other ideas?



THANKS


FWIW, we were in iuka MS at Aqua Marina knocking out a list of mid-loop repairs. We were shocked to discover that one of the bolts connecting the shaft to the tranny coupling was finger loose. The tech ascribed it to whoever replaced the engine mounts which was a condition of sale. He spent 2-3 hours with feeler gauges and adjusting motor mounts to tolerances of .004” if I recall. Might be something there you can use and good luck. My new Mainship had a vibration at 1600 rpm on the SB side I gotta track down as well.
Derek is offline   Reply With Quote
Old 12-08-2022, 05:21 PM   #25
Veteran Member
 
City: Knoxville TN
Vessel Model: Mainship 390
Join Date: Feb 2008
Posts: 46
Update: The prop (28") and new shaft were installed. Vibration is still there. They temporarily put on a smaller prop (25", 3-blade) and the vibration went away. The theory is that the 28" was actually too large and too close to the hull.

Does anyone happen to know what the original Prop specs were for a 2000 MS 390? Wondering if it actually shipped with something smaller than the 28". Thanks.
Souvenir is offline   Reply With Quote
Old 12-08-2022, 07:31 PM   #26
Moderator Emeritus
 
Comodave's Avatar
 
City: Au Gres, MI
Vessel Name: Black Dog
Vessel Model: Formula 41PC
Join Date: Jul 2015
Posts: 18,033
Did you measure the gap between the blade tip and the hull? I believe it should be a minimum of 10% of the prop diameter and preferably 15%.
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you aren’t one, there is no explanation possible.
Comodave is offline   Reply With Quote
Old 12-08-2022, 07:57 PM   #27
Veteran Member
 
City: Knoxville TN
Vessel Model: Mainship 390
Join Date: Feb 2008
Posts: 46
Comodave: No - I did not know about that measurement. I'll try to find that out. Boat is back in the water now, but maybe I can get more info from the technician that's been doing the work. Hoping to find out what size prop the boat had on it when it was manufactured.

Thanks.
Souvenir is offline   Reply With Quote
Old 12-08-2022, 08:05 PM   #28
Senior Member
 
lwarden's Avatar
 
City: San Diego
Vessel Name: North Star
Vessel Model: Lindell 36
Join Date: Jun 2020
Posts: 378
I have seen where three blades can cause less vibration than 4 blades of the same size. This was due to effect of the blades going by the strut and the theory was that because the 4 bladed prop had two blades passing the strut at the same time it caused increased vibration over only one blade. This was for a Shamrock which has a distinctive keel/strut arrangement.

My point is that it if your existing prop were 4 bladed it would be interesting to try the same size in 3 blades if the tip clearance doesn't turn out to be the issue.
__________________
North Star
Lindell 36, Twin 370hp Cummins
lwarden is online now   Reply With Quote
Old 12-11-2022, 12:20 PM   #29
Senior Member
 
Cold Duck's Avatar
 
City: Discovery Bay
Vessel Name: Cold Duck
Vessel Model: MS 350 Trawler, 1997
Join Date: Jul 2022
Posts: 196
I know that in aircraft certain props (mfr) will not work with certain engines due to counterweights on crankshaft or other balancing issues. Also, the way the prop is put on in relationship to the crankshaft can cause a vibration. I don't see why this wouldn't also apply to boat engines. So, one prop will work great with a Yanmar but vibrate with a Cat. Or shaft at tranny needs to be rotated 90 degrees to align with the crankshaft. So many possibilities.
Cold Duck is offline   Reply With Quote
Old 12-11-2022, 05:53 PM   #30
Senior Member
 
DrissZougari's Avatar
 
City: (Cypress Landing) Chocowinity, NC
Vessel Name: BZ interlude
Vessel Model: MS390
Join Date: Mar 2019
Posts: 207
I had some vibration om MS390 with same engine around 2k that was traced to my strut bearing.
good luck,
DrissZougari is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Trawler Port Captains
Port Captains are TF volunteers who can serve as local guides or assist with local arrangements and information. Search below to locate Port Captains near your destination. To learn more about this program read here: TF Port Captain Program





All times are GMT -5. The time now is 10:28 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2023, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012