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Tranny noise |
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FUN-9C1 
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Joined: January-29-2004 Location: Lakes Region NH Status: Offline Points: 206 |
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 Topic: Tranny noisePosted: April-11-2017 at 2:42pm |
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HI all, Been a while since I've posted here. I noticed last fall and again today after "summarizing" the boat that the transmission has a sort of rhythmic clunking sound while the motor is running, and the prop spins a little in a jerking motion. It would probably take like a full minute or two to make one revolution but it does move. It was rebuilt about 5 years ago or so by a reputable shop I think this site referred me to him. Eric was his name. Maybe he's still here? Does what I describe mean anything bad? Fluid is good and it seems to work fine.
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'86 2001
'50 Century Imperial Sportsman |
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KENO
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Joined: June-06-2004 Location: United States Status: Offline Points: 10648 |
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Posted: April-12-2017 at 1:30pm |
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I think that without hearing the noise it could be tough to say for sure but I think it's not a problem.
Cold transmission fluid, no load on the prop and the clutch plates can grab ever so slightly and you'll hear some noises and the shaft can creep. Fluid warms up and the creep stops. With 5 years on the rebuild, you shouldn't be having problems like a dirty neutral and with your description of 1 revolution in a minute that's nothing to worry about. Or it could be your damper plate making the noise if your idle speed is real low. The male splines on the transmission input shaft rattling against the female splines on the damper for lack of any better way to describe it. That's without hearing the noise, but those are my thoughts |
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FUN-9C1
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Joined: January-29-2004 Location: Lakes Region NH Status: Offline Points: 206 |
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Posted: April-12-2017 at 2:43pm |
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That's good to hear. All conditions were as you describe. Basically cold, no load, low idle speed. I do believe if I remember correctly from last fall, there was no noise in gear and it worked fine. Looking forward to checking out under different conditions, but still ice on the lakes here. Thanks for the reply!
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'86 2001
'50 Century Imperial Sportsman |
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SNobsessed
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Joined: October-21-2007 Location: IA Status: Offline Points: 7102 |
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Posted: April-12-2017 at 8:07pm |
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Damper plate.
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“Beer is proof that God loves us and wants us to be happy.”
Ben Franklin |
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FUN-9C1
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Joined: January-29-2004 Location: Lakes Region NH Status: Offline Points: 206 |
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Posted: April-12-2017 at 11:37pm |
Thanks for the reply. Would you mind expanding on that a little? |
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'86 2001
'50 Century Imperial Sportsman |
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Dreaming
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Joined: May-21-2010 Location: Tacoma, WA Status: Offline Points: 1870 |
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Posted: April-13-2017 at 2:01pm |
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Chris is saying that the damper plate (like the flex plate in your automatic transmission car) is causing the noise/problem, the flex plate absorbs the vibration and torque difference between your engine and transmission input shaft. when they get old, the springs weaken and they can chatter. This usually happens at idle since engine operation gets smoother at higher rpm.
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KENO
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Posted: April-13-2017 at 2:56pm |
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Here's an old thread on damper plates complete with pictures.
Maybe you replaced yours when the transmission was rebuilt, maybe you didn't I wouldn't go jumping to any conclusions though till you have it in the water and see how it behaves and make sure your idle speed isn't too low. and the engine idles smoothly otherwise a perfectly good damper and bad running engine can make some hellacious noises old thread And if you tear up the damper by spinning the hub and destroying the springs, the noise is really impressive. |
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8122pbrainard
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Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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Posted: April-13-2017 at 6:23pm |
Been there and done that!!  If I remember correctly, I probably said something like WTF is that noise!! It blew at the end of the season and my next trip up was New Years. I ended up R&R'ing the damper in the boathouse under a tarp with an electric heater going. It was -15 the previous night and that block, trans and bell housing never warmed up. 
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RammerJammer
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Joined: June-02-2015 Location: VA Status: Offline Points: 73 |
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Posted: May-30-2017 at 10:31pm |
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I hope this isn't too much of a threadjack, but does a perfectly good damper plate always chatter when in gear at low (<500) rpm? When I first crank my Excel it takes a few minutes to warm up the rpms to the 600-700 range. Until then, if I move forward or aft the damper plate chatters. Once the rpms are normal, and for the rest of the outing there is no chatter whatsoever and the trans is perfectly smooth.
I hope to make it through the season before I have to change the damper plate. With a v-drive I assume the easiest way to replace is to move the engine, leaving trans and v-drive in place? |
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1991 Nautique Excel, PCM 351, Pro-Tec ignition
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KENO
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Posted: May-30-2017 at 11:09pm |
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In your case I'd be tempted to say something like "tune up the engine so it idles better and don't worry about the damper plate"
Oh wait, I just said it  Or let it warm up so it idles normally before putting it in gear At your less than 500 rpm speed I think the noise is pretty much expected. |
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8122pbrainard
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Posted: May-30-2017 at 11:40pm |
It's not the damper that chatters. It's the planetary gear set in the trans making the noise due to vibrations from the low RPM.A brand new damper will do it. As ken mentioned, get the turn up! 
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SNobsessed wrote: