MD2B gearbox seized: overheated?

UserError
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MD2B gearbox seized: overheated?

Post by UserError » Thu Apr 05, 2018 4:26 pm

Hello,
Following my overheating escapade (forgetting to open the water inlet cock), I'm on the boat & have checked for fuel delivery & the impeller is ok for now. Engine started easily.

However, I can't get it in gear. It was ok (was very stiff when I got onto it two weeks ago) but had freed off nicely. It has now had nearly two weeks idleness and I can't get it into gear. I can see the prop shaft taking up the drive when I push the gear button in, but I don't want to push the lever too hard.

Next thing is to lever the gearbox arm. Edit. Couldn't get a purchase on it. Hmm.

What damage can overheating do to the gearbox?
Thanks
Jonathan
Centaur Polly B
Littlehampton

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Re: MD2B gearbox seized: overheated?

Post by BrightStar » Thu Apr 05, 2018 8:40 pm

I would be surprised if the gearbox is damaged by running for a restricted time without cooling.

Are you saying it wad stiff before?

Check the oil level - often missed and allowed to get dry.

The overheating could have damaged the cable, easy to check, disconnect it from the selector arm n top of the gear box, it ishould then move in and out of gear easily. This would point to a problem with the cable or control lever.

Can you turn the propshaft easily? That rotates the gear box output drive.

When you ran the engine, did it rev up OK, these are robust units with a bit of TLC
Brightstar
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Re: MD2B gearbox seized: overheated?

Post by UserError » Thu Apr 05, 2018 11:30 pm

Brightstar,
Thank you for this. We probably had 20-30 minutes before the engine stopped due to no water. We were going fairly slowly with the tide so it wasn't working hard, but that is not the tlc that the engine needs...

Some hours after the engine had stopped & I had patched the melted exhaust, I tried the engine again (with water this time) & it ran. Is there any water seal in the gearbox that could have been damaged by dry running, then let water in when I tried again later? I will check the oil for water contamination.

When I first started the engine (after maybe 2 years on non-use), I couldn't get it into gear although then I also didn't know how the system worked. I sprayed the throttle lever & knob actuators in the engine compartment with WD-40 and rotated the gearbox actuator arm with a spanner in the securing bolt - didn't need a great deal of force. After that it was fine.

I checked the oil level today & it was low. I think it was just on the dipstick. I topped it up & it is now between the marks.

The cable looks like it wants to move - there is a bit of movement in the slack in arm/cable joint.

The cables look newish -in pretty good condition with bright steel parts.

I had a go at removing the split pin that holds the gear cable clamp onto the actuator arm, but I knew that the pin would disappear into the bilge (even though it was then dry, having lost a water pump screw in there earlier). I decided against that course of action.

I removed the cable restraining bracket to improve access but didn't think to check cable operation.

The engine revved ok - off the tacho, the rev range is less than the arc of the throttle lever, it was at full revs before the lever was fully over. It was sensitive to gentle throttle movements, idled at about 1000 and could be controlled to any rpm. And sounded well, no wheezing or noises.

Before I topped up the gearbox oil, on pushing the gear knob in to engage drive I could see the prop shaft nearly creeping round. However, after topping up, it didn't appear to do this, but I still couldn't get it into gear F or R.

I didn't try turning the prop shaft. Should I be able to do this by hand on the visible section between the stern gland & gearbox?

I will try and remove either end of the gear cable to check that it slides freely. I was also contemplating giving the gearbox actuator arm a modest tap with a hammer in case it had seized. Is that a really bad idea?
Many thanks
Jonathan
Centaur Polly B
Littlehampton

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Re: MD2B gearbox seized: overheated?

Post by TyroSailor » Sat Apr 07, 2018 3:58 pm

One of the major problems that prompted the replacement of my MD2b was the gearbox creeping - it would turn the prop slowly without either gear being engaged, and when I did try and engage there was a horrible crashing sound and the whole engine shook. On inspection (eventually - long story) there proved to be no oil in the gearbox, despite a recent service (and the protestations of the engineer whod carried it out).

It did work after that though: once I was able to get the gearbox filler nut off I flushed it out with oil several times, until particles of metal stopped coming out, and refilled it. So that should be possible, if necessary.
Experience: That which would have been most useful five minutes before you acquired it.

Steve
Tyro (Centaur 1361)
at Southampton

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Re: MD2B gearbox seized: overheated?

Post by UserError » Sat Apr 07, 2018 5:39 pm

Tyro,
The creeping such as it was, stopped when I topped the oil up. It didn't turn the prop, just a bit of clutch drag or similar..

How did you flush it? By sucking it out or is there a drain plug?

FWIW, I can easily turn the shaft by hand.
Cheers
Centaur Polly B
Littlehampton

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Re: MD2B gearbox seized: overheated?

Post by UserError » Sat Apr 07, 2018 6:28 pm

I've just sucked the oil out & put fresh in.
This is what came out- it looks to me as if it has water in it as it is a greyish opaque colour, but not like the mayonnaise you get in a car with water in the oil.
Thoughts?
Many thanks
IMG_20180407_182224145.jpg
IMG_20180407_182224145.jpg (36.07 KiB) Viewed 1317 times
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Re: MD2B gearbox seized: overheated?

Post by BrightStar » Sat Apr 07, 2018 10:53 pm

I dont think there are any seals on the cooling coil, so nothing there to get damaged, did you say you could move the selector arm using a spanner without force, if that is still the case then the problem is likely to be the cable or the throttle lever linkage.

I suggest that you disconnect the cable from the actuator and see if both the cable and the gear box actuator move freely. If the actuator moves, put it into neutral, start the engine and then select F and A by moving the actuator - this will prove the gearbox is ok.

That there was some oil in the gearbox means it probably hasnt suffered from lack of oil.
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Re: MD2B gearbox seized: overheated?

Post by UserError » Sun Apr 08, 2018 3:17 pm

Brightstar,
Many thanks.
Encouraging re the oil being present.
Two weeks ago I used a ring spanner on the actuator arm with moderate to low effort & that freed it & it was OK thereafter. Until now, now I can only move it by tapping it with a hammer.

Yesterday I looked closely at the cable & attachment. The (small) split pins are on the side away from the viewer & not easy to access with limited space. I WILL drop these onto or under the engine and there is an area under the engine which I cannot reach, so I want to be really convinced that the cable is at fault before going through that pain. Both throttle & gear cables look to have been renewed at the same time and look good as shown below. Both cables ran freely. The throttle cable still does: IF the overheating had caused the grease to run out of the cable or some other trauma, surely both would have been affected as they are in the same space? What could have caused only the gear cable to seize?

I ran out of time yesterday but was wanting to remove the actuator arm (circled parts 50 and/or 56) - that would then allow the cable to move or otherwise. Is this a straightforward remove/replace operation?

I will have a fresh go at undoing the cable next time, just to rule it out.
MS gearbox exploded diagActuator.jpg
MS gearbox exploded diagActuator.jpg (141.01 KiB) Viewed 1294 times
Gear cables Lite.jpg
Gear cables Lite.jpg (381.25 KiB) Viewed 1294 times
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Re: MD2B gearbox seized: overheated?

Post by BrightStar » Sun Apr 08, 2018 8:33 pm

If you can only move the gear lever by hammering it, you clearly have a problem and need to isolate the problem to either the cable or the gearbox, it should move freely with almost no resistance.

I cant believe the engine space got hot enough to damage either the cable or the gear box.

Does it make a difference if the engine is runnng?

Alan
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Re: MD2B gearbox seized: overheated?

Post by UserError » Sun Apr 08, 2018 10:06 pm

Alan,
Many thanks.

I will get the cable off to confirm.

Re heat: I'm increasingly of the opinion that it is somewhat or entirely coincidental. The only other thing that occurred - it was dead calm with no seas to speak of all day - was that we were towed at 6 knots by the lifeboat* Could the prop rotating in reverse at speed for 2 hours done anything? Clutching at straws looking for a cause!

I tapped it round on the offchance it would free off.

Re engine running. Unfortunately no difference, and not even with fresh oil in. I will also try getting it into gear & starting the engine - maybe some grot has got into a sliding part & is preventing it from moving & being rotated will eject it. I've got nothing to lose.

Cheers
Jonathan
*no engine and wind completely died to a glassy sea. Tide was changing & would have carried us onto the rocks of Selsey and my daughter had got wet in the morning & couldn't warm up all day and we were beginning to get concerned for her.
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Re: MD2B gearbox seized: overheated?

Post by Jolly Roger » Sun Apr 08, 2018 11:04 pm

Jonathon

Looking at the latest photograph, the lever on the gear box looks quite rusted. I wonder if this has increased the friction and is stopping it from moving. Worth checking out as that would be a simple fix.
Roger
Concerto Fulmar FR38
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Re: MD2B gearbox seized: overheated?

Post by UserError » Mon Apr 09, 2018 7:18 am

Roger,
I've found the service manual for this. (here if anyone else is after it: http://boatinfo.no/lib/volvo/manuals/ms-msb.html#/0)

Next opportunity I'm going to take the actuator assembly off & have a look. Given the nonsensical cost/lack of availability of parts, I'm not sure if there is any value in digging deeper.

Regards
Jonathan
Centaur Polly B
Littlehampton

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Re: MD2B gearbox seized: overheated?

Post by BrightStar » Mon Apr 09, 2018 10:34 am

As Roger said may be worth soaking the mechanism in penetrating oil or diesel to ease the selector shaft throgh the top cover, could be seized there, also a good wire brushing around the shaft may help
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Re: MD2B gearbox seized: overheated?

Post by UserError » Mon Apr 09, 2018 10:53 am

Thanks,
All good info.
Much appreciated.
Jonathan
Centaur Polly B
Littlehampton

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Re: MD2B gearbox seized: overheated?

Post by TyroSailor » Wed Apr 11, 2018 2:26 pm

I got the oil out by sucking with an oil pump. It didn't remove all the oil, but I did it several times, refilling with filtered oil in between, so it was effectively all done. Lots of little bits of metal came out!

There is a drain plug on the bottom, which is almost impossible to get at and probably seized on so tightly that it wouldn't come undone anyway. There's also the drain plug for the coolant pipe that runs through the gearbox - that was almost as hard to get at and undo.
Experience: That which would have been most useful five minutes before you acquired it.

Steve
Tyro (Centaur 1361)
at Southampton

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