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Skipper
06-25-2008, 07:54 AM
The issue:
In neutral, at idle, the transmission produces some clunking noises and the shaft spins very slowly. No problem shifting, accelerating, holding speed, or decelerating.

The boat:
1995 Prostar 197, standard EFI engine, 1:1 transmission, 520 hrs.

I suspect I am in need of a rebuild. My previous experience is limited to Velvet Drive transmissions. Any ideas?

trickskier
06-25-2008, 08:40 AM
Does your shaft have a keyway in it?

Skipper
06-25-2008, 09:40 AM
Does your shaft have a keyway in it?


Yes, no issues with the driveshaft from prop to coupling.

Hunterb
06-25-2008, 02:48 PM
The slow spinning shaft is fairly common and not necessarily a sign of a transmission problem. The clunking may be your damper plate. It's the thing that goes between the flywheel and the transmission and it has a number of springs etc. in it. They are inclined to make funny noises at idle sometimes. Unfortunately you have to remove the tranny to check it. I would look very closely at that before I had the tranny re-built.

Bruce

kawagaskier
06-25-2008, 03:15 PM
It only does this in neutral? I had a similar problem with my 85 S&S, but in gear at idle. Turned out my idle speed was a little low. I adjusted the idle up to about 750rpm and the clunk was gone.

Much2do
06-25-2008, 03:52 PM
Is the clunk heard when you shift into gear or while you at idle idle out of gear?

If it's simply an excessive clunk shifting into gear then replacing your transmission fluid may solve it.

trickskier
06-25-2008, 03:56 PM
Yes, no issues with the driveshaft from prop to coupling.

If it's making a ticking noise, then the keyway is going bad. My 82' had this same problem and the driveshaft finally came out hitting the rudder and damaging the prop........I had to replace the shaft & the prop.

Pull the shaft and inspect the keyway area.

Skipper
06-26-2008, 05:28 AM
It only does this in neutral? I had a similar problem with my 85 S&S, but in gear at idle. Turned out my idle speed was a little low. I adjusted the idle up to about 750rpm and the clunk was gone.


Not an idle issue, in fact the idle is a little high.

Skipper
06-26-2008, 05:29 AM
Is the clunk heard when you shift into gear or while you at idle idle out of gear?

If it's simply an excessive clunk shifting into gear then replacing your transmission fluid may solve it.

Not really making a clunk when I shift. The shift is just fine. It is just that when the engine is idling there is excessive clunking or rattling noise coming from the transmission. I change the engine oil and transmission fluid every 25 hrs.

Skipper
06-26-2008, 05:31 AM
If it's making a ticking noise, then the keyway is going bad. My 82' had this same problem and the driveshaft finally came out hitting the rudder and damaging the prop........I had to replace the shaft & the prop.

Pull the shaft and inspect the keyway area.

Not really a ticking noise.

Skipper
06-26-2008, 05:32 AM
All good suggestions. I will continue to troubleshoot and look at the things you have all mentioned.

trickskier
06-26-2008, 06:24 AM
Not really a ticking noise.

I would inspect the keyway anyway. If it's not that, it's certainly internal and needs attention.

Skipper
06-26-2008, 10:37 AM
I would inspect the keyway anyway. If it's not that, it's certainly internal and needs attention.

I will. I certainly don't want to lose the driveshaft at speed. (or at all, really)

trickskier
06-26-2008, 10:52 AM
Mine came out when I backed off the throttle.

gigem75
06-26-2008, 03:12 PM
Try taking a cut off broom handle about 3 feet long and put it on different parts of the engine, trans, and bell housing and the other end up to your ear to isolate where the noise is coming from. If it's loudest at the bell hounsing I'd go with damper plate.