Slipping clutch/gear on Yanmar 1gm

[Ormenlange]

Hunter 1983 27'... with yanmar 1gm that has never been in salt water.... when you put the engine in gear it moves but slow and then after 30 seconds to a minute there is a clunk sound and it gets full 'torque'.. what is slipping and how do you fix this?

Other info... has been doing the bove for a number of years... then about a year ago the engine would stall out after putting it in gear.... I finally figured out this was a bad engine mount... shaft out of line to drive.... don't really think this had anything to do with the first 'slipping' problem.

 

[kloudie1]

Could be a badly adjusted shift cable or lever.. Try removing the cable at the transmission and shifting by hand .. if the problem disappears, shift cable needs adjusting by loosening the cover clamp and sliding it until the cable can get the lever into gear. If that isn't it the bad news is probably that the "forward" cone clutch is glazed or worn and a transmission tear-down will be required.. The oil level is correct and the correct oil type, right?
In "General Downloads" section, around page 200 of the link below, the transmission settings etc are discussed..:
https://sbo.sailboatowners.com/downloads/Hunter_gen_75448537.pdf

 

[Ormenlange]

I'm 99.9% sure it is not the cable adjustment... gear locks in nice but then the prop turns slow for the first 30 seconds or so (I've actually hung on to the rudder and watched this from under the boat) then there is a 'clunk' sound and the prop spins faster. I don't really see how the cable adjustment could cause this, but correct me if I am wrong.

 

[Whatfiero1]

90% of time it's cable stretch or a stiff cable not putting tranny into gear fully. Again do what Kloudie said and disconnect cable at tranny and manuel put in gear listen for instant clunk then replace or adjust cable. How bout reverse is that working correct

 

[njlarry]

Try the easy fix first, change the fluid. Could be the cable, could be the transmission discs but also could be worn out dirty trans fluid. I would try changing the fluid once or even twice before anything else since you are certain the trans is fully shifting to forward. There is a good chance thst is all it needs. The worst part of transmission rebuilding is getting them in and out of the bilge.

 

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[Ormenlange]

No problem with getting access to the gear box... I've pulled the engine and removed the gear box.... kloude1 has helped a lot... I downloaded the shop manual for the transmission and this is a step in the right direction... I'm thinking it is the cone clutch inside the gear box that moves from the forward gear to the reverse gear. I know it is not the oil level... I drained and replaced the oil a while ago and this did nothing.

 

[Ormenlange]

Just in case somebody comes on this years later... here is what the problem was: The shaft bearing had gone bad and this was causing the little 8hp engine to stall... I think the first problem actually was one of the engine mounts had gone bad as I mentioned... but when I finally got around to replacing this then the shaft was still real hard to turn with it not connected to the engine...