J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Prop Vibration, Slipping Clutch??

Jerry, that's usually a sign that one of the blades isn't opening fully.

The best way I found to test if the vibration is from the prop or the clutch slipping, is to open the engine cover, when the problem is occurring and pressing on the shift lever. If the vibration goes away, then the clutch is the problem. I would almost guarantee that the clutch is NOT fully engaging. In my case, what I finally did was to move the shift connector to the other hole in the shift lever. This put more pressure on the shift lever and in turn, more pressure on the clutch mechanism. This is likely a temporary fix since the reason for the problem is wear on the clutch, but hopefully it will last for a while. The reason the problem can be intermitent can be explained by looking at a shop manual and the way the clutch works. In short, there needs to be constant pressure on the shift lever keep the clutch engaged. When everything is cold, it engages with less pressure, but when the gears and oil warms up it begins to slip.

[This message has been edited by alcal1750 (edited 06-29-2005).]

I had the same problem last year. It turned out to be the main pin in the prop, the one that holds the blades to the housing was bent. I called Martec they sent me a new one, I think shipping was more than the pin, and all has been well since. They said this is a typical problem when the prop needs to be reconditioned. Since I was going into the water that week she said replacing the pin with a straight one should hold me over until this winter when I can send the prop in to be reconditioned.

David

Just to add a little to this thread, my former boat, a C&C 26, had a folding prop, not Martec (Michigan?). It would not open unless I put the transmission in reverse and gave the engine a rev-up before shifting into forward. This was the case when leaving the dock, or when starting the engine at the end of a sail, while still moving at a good clip.
The other day, I experienced the vibration on my J-30 for the first time, and decided to try to same tactic -- it worked! Being an engineer, I have never been able to figure out the dynamics of how or why this works, but I pass it along as something to try before tearing into linkages, transmissions, etc.

To finish off this topic, last spring I ended up having the clutch, transmissioin, reversing gear, whatever you want to call it, rebuilt. The only parts that ended up being replaced in my unit were the drive cone and seals. Total cost $869 including shipping from Portland to Seattle and back. Shifting is now solid and smooth.