Yanmar Problems

[Fr J Hackett]

Has anyone had problems with the raw water pump pulley wearing away the centre locating hole and eventually spinning on the impellor shaft? It's happened twice now and I suspect a combination of poor design and underspecified thickness of the pulley centre coupled with a bit of poor machining of the shaft shoulder are the root of the problem. I am now machining a new centre to be inserted into the pulley to prevent a reoccurance.

Also has anyone replaced the oil seal behind the hand cranking plate / locator, I suspect and hope that it is a relativly simple job of prising out the old one and carefully inserting a new one. As allways comments and advice would be welcome.

 

[sailorman]

wot Yanmar??

 

[charles_reed]

The Yanmar waterpump (and the standard issue Hitachi alternators) have engineeringly inferior pressed pulleys.
I long ago replaced the alternator pulley with a solid machined one (it dramatically reduced slip and extended belt life).

I carry a spare waterpump which can be quickly changed over when impeller, waterseal or bearing goes.
The waterpump pulley goes onto a shaft with two flats on it - I've put two additional washers as well as the single spring washer on either side of the pulley and always keep the nut up really tight. Certainly on one of the pumps the pulley is so untrue that the slightest lack of tension on that main nut would result in the wear you describe.

I haven't changed the seal you describe, but would expect to have to take the front off the timing case to do so.
However I would urge you to check whether you haven't got a leak from the rocker cover, appearing to come from the starting handle dog.

 

[duncan]

so where would you get new (improved) pulleys?

 

[Porthandbuoy]

Yep. Had this happen to the impellers on both engines in my 9m Catalac. The cure was to use a different part number of impeller than that recommended by Yanmar. The problem was the thickness of the impeller. Sorry, can't remember the alternative part No. If you can get your hands on a vernier caliper check the depth of the impeller housing and the compare it with the thickness of the impeller. You could also try a thicker gasket under the housing cover.

 

[Fr J Hackett]

It's 3GM30, yes its possible to buy pulleys with a solid centre or a taper lock fit but I think it will be just as easy to modify the existing one and beef it up a bit. As you suggest a washer at the back face eliminates the poor machining and allows for a better compression and thats how I made made a temporary repair using a couple of star washers.

 

[charles_reed]

Solid pulleys

Any auto-electrician has them, as they are a LH thread with locknut to fit onto the end of an alternator shaft, they would need some pretty heavy modification to fit the Yanmar raw-water pump shaft.

However this shaft/pulley has so little load and rotates so slowly that I really find it hard to visualise the pulley socket becoming distorted UNLESS the locknut had been loose for a long period of running.

This is part of my standard checklist when I carry out the engine oil/filter change at between 100-120 hours.
There are a total of 21 items, besides the oil/filter changes which need inspecting, the 3GM has fewer because of its better balance than the 2GM.

 

[Sailfree]

Re: Solid pulleys

Any chance of you listing your standard checklist? Others experience saves me from having to re-invent the wheel!

Regards
roger