Damper Plate or normal gear noise?

Roy

Well-Known Member
Feb 1, 2003
139
0
Lenox,MA
When I first got my Shamrock years ago I came back to the marina dock and the damper plate or something in there was clanking away. I left it there with a couple of mechanics because it was under warranty. After messing with it they realized it was clanking and the rpms were going up and down. They were puzzled for a little bit but then figured out there was water in the gas and fuel filter. Dumped out the gas and she was back to being quiet. Just another thing to check on the easy side.
 

Sham246

Member
Nov 17, 2022
9
0
Central Florida
First thing I would do is check and change the transmission fluid. Always start with the easiest and check them off the list as you go. Also, look at the shaft coupler, and loose bolts or wear/slop? Then confirm alignment is good, after that I'd consider opening it up to check the damper plate. Chances are it could be that for sure, but why not start on the easy and cheap stuff before pulling the tranny!
I did that, came out clean and looked like it was probably replaced when the engine was. I have a transmission fluid filter on order just because I don't know how old it is. Taking the idle speed to a tad over 600 rpm it goes away completely.
 

idigit

Member
Mar 28, 2022
5
0
Thanks, I saw your post on the facebook group. Did your noise go away with some throttle?
Well, it went away, but the sound was not the familiar purr of the motor & drive line... there was certainly a strange and different sound, so what I did was cut the motor, called the tow boat & took her home.
 

Sham246

Member
Nov 17, 2022
9
0
Central Florida
When I first got my Shamrock years ago I came back to the marina dock and the damper plate or something in there was clanking away. I left it there with a couple of mechanics because it was under warranty. After messing with it they realized it was clanking and the rpms were going up and down. They were puzzled for a little bit but then figured out there was water in the gas and fuel filter. Dumped out the gas and she was back to being quiet. Just another thing to check on the easy side.
That is also on the list. I'm going to pull and check the spark plugs as well.
 

Sham246

Member
Nov 17, 2022
9
0
Central Florida
Well, it went away, but the sound was not the familiar purr of the motor & drive line... there was certainly a strange and different sound, so what I did was cut the motor, called the tow boat & took her home.
Once I throttle up even a hair it goes away and sounds fine and runs all the way to 5K+ rpm no issues. Mostly cruise her around 3400 rpm, very rarely over 4K. You are in Tampa Bay correct?
 

Don L.

New Member
Jan 21, 2022
4
0
My 260 Mackinaw with 230hp Yanmar has the same issue. I replaced the plate with absolutely no change. A mechanic came down and cracked my injectors (at an idle) one at a time. One made a lot of difference, two made a slight difference and one made hardly any difference at all. He told to have the injectors rebuilt cause this could very well be the problem. I’ll post my finding in the next few months. Winter projects do happen here in the Pacific Northwest 😉
 

idigit

Member
Mar 28, 2022
5
0
Once I throttle up even a hair it goes away and sounds fine and runs all the way to 5K+ rpm no issues. Mostly cruise her around 3400 rpm, very rarely over 4K. You are in Tampa Bay correct?
Well, you may be inclined to hire a mechanic, b/c it may not be the damper plate after all.
 

Sham246

Member
Nov 17, 2022
9
0
Central Florida
My 260 Mackinaw with 230hp Yanmar has the same issue. I replaced the plate with absolutely no change. A mechanic came down and cracked my injectors (at an idle) one at a time. One made a lot of difference, two made a slight difference and one made hardly any difference at all. He told to have the injectors rebuilt cause this could very well be the problem. I’ll post my finding in the next few months. Winter projects do happen here in the Pacific Northwest 😉
I don't know much about diesels either, but I watched this video and made me think i was something other than the plate.
 


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