PDA

View Full Version : 71c "Velvet" Neutral Creep - not glazed or warped clutches


Luv2Ski
08-30-2010, 12:01 PM
I purchased a prostar 190 late last year and rebuild the transmission due to a blown reverse gear and a fountain-sized leak from the front seal. I also aligned the engine and replaced the strut bearings with the new style.

Post-rebuild, I have had the dreaded neutral creep. I read on here that creep can occur right after a rebuild as the clutches break in. However, now that I have better than 25 hours on the rebuild, I am thinking this is not going away.

If the boat is idling low (~600 rpm), the prop can easily be stopped by just a little light pressure on the shaft from a shoe or hand. It will typically start spinning again within a minute later.

If I increase the rpm, the shaft will spin faster and it is no longer easy to stop.

I am thinking I may have an internal leak on the gear selector valve that is letting pump pressure into the forward piston; therefore putting pressure on the clutches while in neutral. As the pump pressure increases with RPM, the leak becomes more pronounced and the clutches are driven together harder; which is why I can't stop the prop.


Has this happened to anybody or does it at least sound like a reasonable theory?
Any theories on what needs to be replaced?


I plan on taking the valve out (should be a 5 minute job) and just taking a look. Hoping somebody might have some insights before I start taking things apart.

CantRepeat
08-30-2010, 04:40 PM
If you have creep I believe the forward clutch pack is too tight. The ring that holds the clutch pack come in different sizes. There is a chart that tells you the clearance you must have and to use which ever ring that will allow for the stated clearance.

The clearance on a 71C should be 0.018 to 0.053 and there are 6 different size snap rings ranging from .033 to .100.

Just because you put the same number of friction discs and plates in does not mean the clearance is correct. When I did my rebuild I had to change the ring.

There are also some adjustments you can make to the selector lever.

Here is a link to the service manual that has those adjustment instructions.

http://www.mastercraft.com/teamtalk/showthread.php?t=32581

Luv2Ski
09-06-2010, 03:46 PM
I recall having the gauge out and checking those tolerances, so the shims should be correct. That said mistakes do happen so I will add this to the list of "possibilities".

Can you elaborate on the selector lever adjustments you mentioned? I just skimmed through the manual again and am not sure I found what you are referring to. The linkage to the throttle is correctly adjusted such that the selector is sitting in the neutral detent when the throttle is.

Since my original post I tried reducing the fluid level as I read slightly too much fluid can cause this, but even running it low had no impact.

I think as the next step I will pull out the valve and inspect/clean it. I am trying to avoid pulling out the trans until I am sure it is necessary - and then it will definitely be in the off-season.

Any other thoughts are certainly appreciated.

Thanks for the suggestions! sorry for the long response time, work really ramped up last week and I have not found anybody who wants to pay me for playing on the lake :)