prop shaft backout

[John Boag]

When I backed out of my slip last weekend the prop shaft dis-engaged from the transmission cupling. This left me with no forward or reverse speeds. I got it back together but determined that I don't want that to happen again. My question is, on the A4 all that is holding the shaft in place is a bolt through the cupling with a keeper wire to keep the bolt from backing out. Has anyone drilled into the shaft to created a dimple or drilled through the shaft and added a pin. If so, what size pin did you use. Thanks.

 

[Tom Soko]

Dimple

On my C30 with an A4 I had tightened the keeper bolt to mark the spot, took the flange off the shaft, and drilled a small dimple into the shaft. Replace the flange, tighten the keeper bolt, and wire the bolt in place. You should have no problems after that. I'd be hesitant to weaken the shaft by drilling through it for a pin.Tom.

 

[Briann Smith]

Fix the problem

I have had a similar problem except that I didn't know it until after I dropped the lines from the mooring ball and found myself adrift in a mooring field heading toward shore.When we confirmed the problem I attended at the local dealer for Yanmar engines. Perhaps because I'm a woman I was given great service or maybe it was because I'm a sailor.When the shaft is out of the coupling housing and the bolts holding the housing together are removed it can be seen that the shaft has 2 flat spots on it. This is designed to accept the seating of the two bolts which hold the shaft in place. I understand that the alignment is critical and can cause a vibration if not properly alligned. There are also torque ratings for the tightness of the bolts. You should check with you local dealer.When this happened I contacted the person from whom I purchased the boat and he confirmed that this had happened to him approximately 5 years ago. I am treating this incident as the need to have a twice a season inspection done just to ensure that this doesn't happen again. If you need any further information please email me at mbx@istar.ca Good luck.