Yanmar Gearbox Intermittent Fault

[joliette]

I have a Yanmar 30GMF fitted with a KM8P gearbox, which appears to be developing a fault. When I select ahead the prop shaft doesn't always engage immediately. Sometimes there is a gap of a second, followed by a rattle before it engages. This doesn't happen when the engine is cold but has occured a few times when the engine has had a good run for at least 20 - 30 mins. It doesn't happen when I select astern. I've changed the gearbox oil and checked the selector mechanism but this has not made a difference.

Does anyone have any experience of this problem?

Is this likely to be due to some wear developing in the clutch and causing it to slip? Are these boxes fitted with a cone type clutch? Is this easy to replace, without any special tools? Where is a good source for parts and a workshop manual?

Thanks!

 

[ostra4]

We had a similar problem with our yanmar 3jh engine 2002 vintage .I am not too sure from memory which gearbox we have and boats in Greece.The engine would only go into gear after 1500 revs ish and then with a resounding clunk .After engagement all was fine .It didnt happen in reverse .We had the drive cone replaced (part was 300 odd euro). On examination the reverse side of the cone wasnt worn - as you would exspect . The guy who did the repair told me it wasnt unknown to turn the cone round and start afresh on reverse part . dont know if your box has a cone or what but it does sound a similar fault .You could try asking on yanmar help forum for your engine using google.The mechanic did need to buy two new nuts that need peening over and they were 40 euro !!!!!!!!!!!!!!!! If I ever replace this engine I would have a serious look at parts prices for other makes although I suspect they are all just as exspensive .A replacement engine mounting rubber foot for my is around 100 quid each .400 pounds plus labour if not doing it myself is bordering on robbery .Iv stopped looking at other parts prices as its too worrying .Our engine had done 1250 hours when fault started with no warning .Good luck with your box .

 

[Oldhand]

It could be just your control linkage needs adjusting, have checked the gearbox actuation lever is at full travel when you engage from the remote control?

 

[Niander]

you can get the manual on ebay

 

[Honey]

First check all the obvious as others have stated!
You say your gearbox is a KM8P but my paperwork only lists a KM3A or KM3P for this engine. Both of these have a cone clutch which has a tendancy over time to become "glazed" and may need to be roughened up. Also the KM3P has a damper disk with springs like the centre section of a standard car clutch.
Somebody may be along to tell you where to get the manual (a dutch site) but if not PM me and I will try to email it (65mb)

 

[Honey]

This site has the manual to download - 240 pages - 65mb

http://www.motoren.ath.cx/

 

[joliette]

Thank you to you all for your help. I will check the selector once more, but I don't think that's the problem. This will have to go on the winter to do list. I will take a look at the cone and either rough it up or reverse it, before I fork out for a new one!