Yanmar 1GM Gearbox

[Evadne]

Has anybody got any tips on removing the bell housing from the main engine? I finally got all the bolts out but the bugger won't move. I need to get the gearbox off as its leaking oil from the shaft bearing. My otherwise helpful workshop manual is as succinct as a Haynes manual on this one, "Now seperate the two", and having had experience of the fragility of Yanmar castings I'm reluctant to try the Bigger Hammer technique unless all else fails.
Thanks.

 

[cindersailor]

I have had the bell housing with gearbox attached off on my 1GM without any problem. There are no hidden attachements, just the 8 or so bolts around the outside. I suggest you try to get something (knife blade, chisel ?) in between to try to pry them apart, they are probably just held together by some corrosion/dirt. The other possibility is that the engine to gearbox splines are a tight fit - can't think of a solution to this one other than gentle and even wedging of the bell housing off the engine and a liberal spraying with WD40 with a ling tube.

 

[Evadne]

Thanks, I suspect that the splines are welded on, the rim of the bell housing prises away when I get some screwdrivers under it, then pings back when they're removed. It is at least 22 years old and never been apart, I suppose. I think I'll have to go and stock up on WD40.

 

[Birdseye]

As far as I remember, as well as the bolts there are a couple of studs which align into blind holes. So you will not be able to lever laterally - just lengthwise.

Other than that it seems likely that rust is binding the splines. Dont know what to suggest except to phone John Skewes at Cellar Marine in Porthallow Cornwall - Yanmar agents and really helpful genuine Engineers as opposed to spare parts salesmen.

 

[Rabbie]

Whilst we are on the 1GM gearbox subject. Can I ask anyone what is the correct oil for the gearbox and how much do I need. (Lost the manual!) Thanks. /forums/images/graemlins/confused.gif

 

[cindersailor]

Information on the Yanmar Web Site (sorry cannot find the url) says that the geabox oil should be SAE30 mongrade oil. Monograde oils are not easy to find, but halfords sell SAE30 for garden machienery (lawn mowers I assume) in 1 litre green bottles. This should last a while as it only takes 250 ml as far as I recall. I have used this for a full season with no problems. However, I cannot believe that a gearbox for a 6.5 hp engine is a very demanding application and 10W30 multigrade would probably be fine.

 

[ShipsWoofy]

The manual for the modern engines state exactly the same oil as the engine.

Must admit, I should really think about a drain and refill on mine, yippee, climb over the engine and working blind.

 

[Evadne]

Thanks

Thanks for the advice, there are only the 8 bolts, no lugs (it rotates) so I've chickened out and asked my local expert to have a go. He is less likely to crack the bell housing than me while getting it off, and at this time of year, time is money (his time, my money).

With the leak I've got in the gearbox I don't need the arms of an octopus, it is self-draining.

The manual says the same as the engine oil (SAE 10-40) for my old 1GM as well.

 

[steve28]

Re: Thanks

dont forget to check the oil level on the gearbox with the dipstick unscrewed, there are quite a few people i have heard off who fill it up far to much because they check the level when its screwed in.


steve

 

[Evadne]

Re: Thanks

/forums/images/graemlins/confused.gif Surely if it's screwed in you will underfill the gearbox?

 

[steve28]

Re: Thanks

the level is designed to be checked with it just resting on the threads, maybe i worded it wrong /forums/images/graemlins/smile.gif


steve

 

[Rabbie]

Woofy. I just HAVE to change mine!. You should try it in a Snappie!. Its like worming your way into a torpedo tube lined with barbed wire!.

 

[corncob]

Dave, The splines are rusted into the damper plate, WD40 is all I can suggest. You will need a new damper plate after you have finished. When eventualy removed, reinstall using teflon grease, or copper slip on the gearbox splines, it won't happen again. SAE30 specified for engine and gearbox if you can get it. use 15w40 standard diesel oil. Yanmar do thier own, if you are still having problems, the guys at Yanmar are helpfull?