Shaft turning in neutral

[WAC]

Hey guys after a long 10 months of labor I finally got The Old Broad in fighting shape for the season. While out fishing the other day I noticed the starboard prop shaft slowly turning while in neutral drifting a spot. Enough to push the boat into doing slow circles while drifting. If you rev the engine it is fine and in neutral but it still lopes along with a slow turn. It is like there is enough friction or drag somewhere to cause it to turn. This is my first inboard boat so this is a new issue to me. Any suggestions on what could cause this? Currently have to shut down the starboard engine to carry out a short spot drift. Thanks.

[Charlie J]

tranny need to be rebuilt

[Bill Fuller]

WAC
Assuming you have a Borg-Warner velvet drive tranny, I would guess that the tranny has actually been rebuilt and the forward clutch pack was set too tight.
I have seen this symptom numerous times and had the same problem the first time I rebuilt one. I have subsequently re-adjusted the clutch pack on several trannys that had this problem.
The problem is that the recommended clearance of 0.035"-0.055", for the bronze clutch pack, is too tight on the tight side of the spec. It seems that most people set the clearance on the tight side of the spec, maybe in the range 0f 0.037"-0.040", I know I did the first time. And the result is a tranny that drags in neutral. I ran my own boat for 2 years before I figured out that it was not going to loosen up with time and wear, and pulled it out and set the clearance on the top end of the spec. I suspect you need to, or have someone, pull the tranny, open it up and change the snap ring holding forward clutch pack to obtain the looser clearance, close to 0.050"
Good luck
Bill

[Carl]

Clutch plates warped and rubbing enough to keep shaft turning.


Or your gear linkage has tranny hanging in gear a bit. Remove linkage to verify she's in neutral manually. If a bit out adjust so neutral at shifter is neutral at the tranny.


If warped plates, a rebuild is in need. If adjustment is off, remedy OR it won't be long before a rebuild is in need.

FYI- Tranny can run a long time with warped Plates...down side is boats always in gear when running and that can create some unsafe condition, aside from turning in circles,

[Harry Babb]

I have had the same problem with Velvet Drive Tranny's.

In my experience the problem is the "Bellville Spring" that releases the forward clutch when transmission is in neutral......has lost some of its shape.

It seems that most rebuilds consist of seals, seal rings, gaskets and clutch packs. I think these parts came in a "Kit". The spring that I am talking about did not come in a kit....had to be purchased separately.

The first one I ever rebuilt was because it was Draggin....new clutches and seals.....did not correct the problem....took it back apart and replaced the Belleville spring and walla! ! Problem solved...

hb

[aussierob]

Some good advice here based on my understanding.

I know my velvet drives turn at idle when in neutral, which i don't think is uncommom (especially in Winter here when the transmission fluid would be quite cold), however that's out of the boat with no props attached, and only because there's nothing really stopping it. You can easily stop it by hand - certainly not enough friction there to turn the output coupling when disconnected from the shaft.

I never saw the shaft turn when in the boat at idle / neutral.

They're the most amazing transmissions, but do seem to either slip or bind if not precisely in the sweet spot. I'm overhauling mine while repowering, and will be making sure everything is working as much as possible before putting them back in the boat (will probably run them for an hour or so assembled with their respective new engine, so i can check for noise / temp / oil levels etc - i'll be doing carb tuning / oil leak checks anyway).

Rob

[WAC]

Hey guys yes they are velvet drives. That is some good information. I was going to try the linkage first to see if it is creating some sort of drag. So I will try that this weekend. If it continues I think I will deal with it for the summer then pull it over the winter and have a look.
With just finishing a complete rewire, new gauges, floscans, new pumps, plumbing, refinishing 50% of the teak, LED lighting, new heat exchangers, new exhausts, and rebuilding both alternators, funds are thin. She is running great but not sitting still, is bothersome.
Thanks for the suggestions. I will post when I figure it out.
Hoping for a linkage issue or the simple fix. But I'm usually not that lucky.