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cburger · 13-02-2008, 08:16

I would like to help out a friend who is having problems with his Yanmar tranny. It is reputed to be a model YM7. My question is a two part one. First I don't think we will have any problem removing the gear from the vessel, but it sounds like the clutch and pressure plate needs replacing. Is this something simple that can be attempted on my bench or something that is best left for experts? Second the gear oil appears to have some water in it, a milky brown consistency, is this a normal look to the gear oil if it hasn't been changed in a long while or indicative of a more serious issue. We have a quote form a very reputable outfit to completely rebuild the gear for $800.00, thoughts?

**Inlet Marine Services** · 13-02-2008, 08:46

We need to know the model of the transmission, is it a straight drive? KM series or an old YM series engine? Is the motor up and down or on its side?

cburger · 13-02-2008, 09:27

It was indicated that this is a YM7 model?

**Alan Wheeler** · 13-02-2008, 10:31

The oil should be clean and clear of any water.
The box will not have a Clutch and pressure plate like a car manual transmission does if that was what you were meaning.
I don't think these little fellows will have a transmision cooling heat exchanger where water could possible enter the box. So you need to find out how water got in there in the first place. If it is just due to lack of maintenance, then he is reaping the rewards of not doing so. Regular oil changes are important.

Drumroll30 · 13-02-2008, 10:41

On a Yanmar 2GM its likely that your tranny is a KMP2. If it is this particular transmission the appropriate lube is regular motor oil, the same used in your engine. If slipping the likely culprit is glazed over clutch cones. Check Yanmar Marine Engine Help for posting Yanmar related questions, many knowledgable sailors and mechanics on there in the discussions section.

**Inlet Marine Services** · 13-02-2008, 11:02

YM7 is not a Yanmar model, there is a YSM 8 or 12, YSB 8 or 12, YSE 8 or 12. Is the motor horizontal or verticle?

cburger · 13-02-2008, 11:50

Thanks all I will have to get back with the exact mmodel number.

cburger · 13-02-2008, 13:34

Tranny model is a YP7M

cburger · 13-02-2008, 14:31

The engine is a 1976 2QM20 not a 2GM20 which was developed later. The motor is up and down, not on its side. There is no transmission label, but I was able to identify it in the yanmar service manual drawing. The distinguishing characteristic is that the shift control is a round rod rather than a flattened lever like the other hurth or KB transmissions.