View Full Version : Yanmar 3gm30 rough vibration in forward gear

07-03-2008, 11:05 AM
"Our 3GM30 has recently developed a very rough "shaking" vibration when engaging forward gear in idle to moderate rpm. Applying full throttle stops the vibration, and it is absolutely smooth in reverse at any rpm. The prop (Gori 3 blade folding)and shaft are perfect. When vibrating, the engine nearly jumps out of it's mounts, and water pours out of the Volvo packing gland. The engine isolator mounts appear tight. Am very good mechanically, any ideas?"

07-03-2008, 01:37 PM
"yes, I have seen this before. I will post at length this evening after work. S."

07-03-2008, 07:59 PM
"ran into this a few years back in san diego. same symptoms as you described. yanmar even sent some engineer types to check it. no one could figure it out. turned out to be the thrust washer on the intermediate shaft. it normally sits in a little pocket in the case. it had somehow become loose and turned on the shaft. was riding against the reverse gear when in forward. it's been a number of years, but as I recall I just put it back in place and it stayed there. anyway, when disassembling the gear. look very closely for this. this gear is by the way, very easy to work on. the hardest part is taking it out of the boat. I have a copy of the parts breakdown, showing the part in question. don't think I can post it here as it is from a copywrited service manual but could send it to you via e-mail if you need."

07-16-2009, 01:50 PM
"Scott, I ignored this issue for the last season, but I now want to get it tackled. Do please email me the parts breakdown page. I was wondering whether it had to do with the transmission. I appreciate your reply."

04-22-2012, 11:37 AM
Was your problem solved? I have the same problem with my 3gm

04-22-2012, 11:43 AM
Am having same problem as pocketchange, I opened the tran. but could not find any defects. I only took out the main shaft that holds the cone clutch . Is the intermediate the one that fits into the damper plate?