This weekend we were finishing our sail home and when we were entering the harbor we fired up the engine. After about 20 minutes the boat shuddered like we hit a large log and we lost thrust. Quickly put it in neutral and checked the bilge, steering etc. we also looked over the stern as soon as it happened expecting to see what we hit (high tide, turbulent water lots of pots). We didn't see anything and everything looked okay below. Tried to put it in gear again, still no thrust. Put it back in neutral and went down to watch the tranny gear arm at the engine. Tried again and the Tranny engaged and worked as normal. Motored for another 40 minutes to the marina with no problems. No vibration, smooth as silk. I tested the Tranny hard right before making the entrance to make sure I had control for docking. No issues. Once tied up, I ran the engine hard to see if I could recreate the problem and I could not. Assuming I did hit something, had a diver check the bottom, drive train etc. All good. No paint missing, prop was good, CB fine.
Based on the sound I started thinking Damper Plate. Although I know this is a pretty well known issue with Universals, haven't really seen much on Yanmars. Spoke with 2 mechanics I trust to get their opinion and both said if I lost the Damper, at the very least I would have vibration and more likely wouldn't be able to put it in gear. So I'm left with trying to figure out what happened. I suppose cavitation is a possibility, but the noise seemed a bit extreme for this. Another possibility would be the cable is not putting the Tranny in full forward. Not likely since before and after the shifting is silky smooth. Here are the specifics:
Yanmar 3YM30 with 250 hours.
Trans oil changed last Fall (rechecked level once we got back)
Fixed 3 blade prop that is properly pitched and was rebalanced two seasons ago by a highly regarded prop shop (once again, thanks Maine Sail)
CB changed out 2 seasons ago and diver confirmed it was good.
Shifter is a single lever throttle/shifter-Edson. Doesn't slip and I checked the tension this Spring.
Since I hate leaving these things to an anomaly, I would appreciate any thoughts on this. I plan on freeing the cable at the engine tomorrow to verify the throw is correct, but I'm out of theories...thanks in advance...
Based on the sound I started thinking Damper Plate. Although I know this is a pretty well known issue with Universals, haven't really seen much on Yanmars. Spoke with 2 mechanics I trust to get their opinion and both said if I lost the Damper, at the very least I would have vibration and more likely wouldn't be able to put it in gear. So I'm left with trying to figure out what happened. I suppose cavitation is a possibility, but the noise seemed a bit extreme for this. Another possibility would be the cable is not putting the Tranny in full forward. Not likely since before and after the shifting is silky smooth. Here are the specifics:
Yanmar 3YM30 with 250 hours.
Trans oil changed last Fall (rechecked level once we got back)
Fixed 3 blade prop that is properly pitched and was rebalanced two seasons ago by a highly regarded prop shop (once again, thanks Maine Sail)
CB changed out 2 seasons ago and diver confirmed it was good.
Shifter is a single lever throttle/shifter-Edson. Doesn't slip and I checked the tension this Spring.
Since I hate leaving these things to an anomaly, I would appreciate any thoughts on this. I plan on freeing the cable at the engine tomorrow to verify the throw is correct, but I'm out of theories...thanks in advance...
