1gm10 - possibly siezed gearbox ???

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zakflak1

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My gm10 is not behaving after a 2 year layup.

Thought I had a stuck valve but whipped the cylinder head off and its not that. Turning the crank I can only get the piston to travel from bottom to top of bore and then 'clonk'. In reverse direction it goes clonk when the piston is at the bottom of the bore.

The prop turns freely (apart from the cutlass bearing grabbing).

The morse control shifts fwd and reverse but not with the button in. ie with the button pushed in the lever wont shift fwd or reverse. Something in the gearbox seized ??? Any ideas welcome, really dont want to take it all out.

rgds
 
If the head is still off then try putting it into gear using the lever on the side of the gearbox (not the morse control). Then if you turn the prop the engine should turn. Note, you cant do this with the head on as you wont get over the compression.
 
gearbox

you have not said if the box is semi automatic or direct manual or any of the rest mixed........but the first thing to do is disconnect the cable from the box and try operating the box directly, you may have to use a spanner or mole grips to get it to go in and you may have to have the engine running, this will rule out the linkage, if you are lucky and it goes in the linkage will just be siezed up and will just need stripping/cleaning/lubricating.
If the box has ATF (red fluid, or maybe dirty red) try draining, flushing and a refill, it may just be that the fluid is no good after the lay up. come back and let us know how you get on.
Oh, and try the linkage when its disconnected to make sure it OK, both in neutral and in gear.
 
Thanks for the replies.

Its a manual gearbox, two direct cables from the morse. I cant run the enginge as it wont turn over fully. I had tried shifting from the gearbox lever but havnt disconnected the cable yet, I thought there was a bit of movement in the cable but will check with it disconnected tommorrow.
On a quick look in the dark it felt like the lever was moving but coming up against a hard stop in the gbox, I'm guessing the drive cone could be stuck on the shaft?

rgds
 
g/box

you need to try and isolate where the problem is, is it the linkage, or is it the box. if the box is accessable then whip it out, at least then you have the worst case and a re-build may be possable, you could try a none marine gearbox re-build, if its not too bad.......it may be something stupid when you take it out and a cheap quick fix may be poss.
you have not said what make of box it is.
 
Zakflak1,

"....with the button pushed in the lever wont shift fwd or reverse...."

With the button pushed in the lever should only operate the throttle. If the lever won't move you may also have a problem with this mechanism as well as the gearbox.
 
TNT said:
you need to try and isolate where the problem is, is it the linkage, or is it the box. if the box is accessable then whip it out, at least then you have the worst case and a re-build may be possable, you could try a none marine gearbox re-build, if its not too bad.......it may be something stupid when you take it out and a cheap quick fix may be poss.
you have not said what make of box it is.
Click to expand...

TNT -I've PM'd you with a follow-up query/question.

Thanks

Jaba
 
Well its the gearbox seized, there was not a drop of oil in it!!. Think its been leaking out the output shaft seal.

Its having a soak before I split it open. Any thought on what the chance are of repair. I'm guessing the aluminium bronze cone clutch has seized. I imagine Yanmar spares are painfully expensive?

If anyone knows of a second hand one please let me know.

rgds
 
zakflak1 said:
If anyone knows of a second hand one please let me know.

rgds
Click to expand...

The cone clutches wear so any second hand one you find on ebay is likely to be worn out. Caveat emptor.

Dont see why the box should seize when the boat was laid up and doing nothing. And dont see why this would make the cone clutch any worse than it was before lay up - assuming it was working OK then.

In fact the whole thing is puzzling. If you can operate the gear lever at the side of the box and can turn the prop shaft when the box is in neutral then I cant see the clutch being seized.

OK I've not seen the engine and am going on a very few details but I would not be surprised if the problem were the engine and the box being dry is just a coincidence. After all, the clunk comes at full movement of the piston.
 
Hi Bosun/All

Yes it was puzzling me, but now an update, right or wrong I flushed and filled the removed gearbox with diesel over night, flushed again then refilled with 10/30w, little by little its just about turning now, the output shaft turns fine, the shifter shifts although a bit stiff, the input shaft turns but is very stiff in one spot that seems to move around?

Have to go out now but I flushed and filled with diesel again and I'll have another go tommorrow.

I definately need new oil seals. Thoughts anyone?

rgds
 
zakflak1 said:
... the input shaft turns but is very stiff in one spot that seems to move around?
Click to expand...

The input shaft drives pretty much everything in the box all the time. What you describe sounds like a failed/failing bearing.

The procedure for splitting the box is in the workshop manual (available on line). I haven't studied it in detail, but at a glance it looks fairly straightforward to split the box and check the bearings without dismantling the output shaft / clutch assembly. (Input or idler shaft bearings might be favourites as the are physically the highest in the box and would have been out of oil for the longest.) If it's the bearings in the clutch assembly, then it's a bit more involved.

Andy
 
zakflak1 said:
I definately need new oil seals. Thoughts anyone?

rgds
Click to expand...

Take the box out, strip it and replace all bearings and seals. The parts will be available at sensible prices from bearing factors.

It's the only way. Even if you get the box to turn properly, you really need to check it out internally. Look for heat marks on the gears etc.
 
theoldsalt said:
Zakflak1,

"....with the button pushed in the lever wont shift fwd or reverse...."

With the button pushed in the lever should only operate the throttle. If the lever won't move you may also have a problem with this mechanism as well as the gearbox.
Click to expand...

This is what I was thinking. The button pressed in disengages the gearbox allowing you to run the engine at higher revs without going through the gearbox.
It'll be stiff (try a spanner on the prop nut, maybe), but can you turn the prop with the lever forward or aft with the button OUT? ... I'm no mechanic so could talking BS.
 
Need a new gearbox

Eventually got round to stripping it down, most of the gears have chipped teeth, the rear oil seal was badly gone, so probably ran for some time with little or no oil.

I need a new gearbox, ouch! If anyone hears of a 2:21 gearbox for sale please let me know.

Thanks for all the advice.
 
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