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Clunk when I shift into Gear

Nov 26, 2012
1,167
Hunter 34 Berkeley
I have been posting on my transmission issues for awhile now. Still not quite there. I have a Yanmar 3GM30F with a Kanzaki KM3A (1984). I actually recently replaced the transmission with a used rebuilt one from EBAY so who knows what I got. Anyway, after it has warmed up a but it clunks when going into gear. It happens in both reverse and forward and it is a bit of a heavy clunk. I do have a Martec folding prop that I had reconditioned by a local boatyard recently so I will assume that it is not the prop for now but I am not eliminating the possibility completely. Anyone else out there deal with this issue? What have you found?
 
Jan 11, 2014
4,644
Sabre 362 113 Fair Haven, NY
The Martec will make a clunk when it opens up, especially when it opened quickly by giving it some throttle.

What did the yard do when they reconditioned it? Why did you have it reconditioned? Martec also provides this service.
 
Nov 26, 2012
1,167
Hunter 34 Berkeley
I had it reconditioned as a way of eliminating it as a possibility with a vibration issue with the previous transmission. It did not really need it. The clunk comes when shifting into gear even at idle. This is new. I have heard that it may be a symptom of an out of adjustment shifter but it is difficult to chase down any solid info on this. Seems that forums are really the only source.
 
Jan 11, 2014
4,644
Sabre 362 113 Fair Haven, NY
According to Martec the test to see if the prop needs reconditioning is close the prop and measure the distance between the blades. If the blades touch then the prop needs reconditioning. The blades should be between a ¼" and ⅜" apart when closed. It is this gap that helps the blades open in reverse.

It has been about 7 years since I had a boat with a Martec, and I do recall the clunking when shifting into gear.
 
May 17, 2004
2,176
Beneteau Oceanis 37 LE Havre de Grace
Is it possible that the clunking is the sound of a healthy Martec unfolding, and reconditioning restored the prop well enough to cause it? I don’t know exactly how a Martec works, but it seems like a worn/unlubricated prop might unfold slowly, whereas a clean fresh one might quickly pop open with a clunk? Although you seemed to say it happens when the engine is warm, and if it were the prop I can’t imagine why it would be different warm vs cold.