Gearbox blues. ( j2 )

[darren620]

i thought i would start a new thread about the gearbox following on from the advise and progress in the last thread. 

 

i can only apologise for its colour. lol. 

 

so. 

 

in the morning after the posts of help and advice. i sussed there was an almost full SAE30's 5l tub of oil and brimmed with a confidence thats perhaps proven to be premature. i decided. ide remove both caps. empty out the oil and establish just how much there actually was in there and, having everything i needed. replace what i found with the correct amount.......

 

what i found can only be described as sludge. the small dribble of oil was easily contained and rubbing my finger around the lower hole the thought went through my head thus:

 

thats the friction plates right there, in that sludge...........

 

and so.....

 

Q1 how who and where do we start to look for new friction plates. 

 

Q2 how hard is replacing them

 

Q3 going between the gears is still really a two handed job on the levers on the wheels. is it possible somethin inside ( presuming i do get in there ) is bent, deformed or just generally worn out????

 

picture for additional dramatic effect.  and yes. thats all that came out. 

 

 

 

 

[MtB]

Ah, on my J gearbox which leaked a little, when the oil level needed topping up and I hadn't noticed, it reminded me by tending to stick in gear. And then it needed two hands and a bit of violence the get it out of gear. Adding oil made this go away.

 

Try just filling yours up with the right quantity of oil and see what happens.

 

 

[darren620]

1 minute ago, MtB said:

Ah, on my J gearbox which leaked a little, when the oil level needed topping up and I hadn't noticed, it reminded me by tending to stick in gear. And then it needed two hands and a bit of violence the get it out of gear. Adding oil made this go away.

 

Try just filling yours up with the right quantity of oil and see what happens.

 

 

hi mate. it got the 750ml that the advice said it should have. its still very difficult to go through forwards to backwards and back again

[BEngo]

Can you easily disconnect the prop shaft from the gearbox?  If so do, and then try a gear change. 

 

The whole prop shaft should slide back and forward  as the gear is changed. Disconnecting it will tell you whether it is the box, or the shaft that is not moving freely.

 

If the box is free investigate the shaft.  It may have a plummer block that wants greasing and/or the stern tube and gland need an investigate.

 

Also check the alignment. It needs to be accurate or the prop thrust will shove the box shaft off-centre.

 

I would incline toward it being a shaft problem, because the box is designed so that the prop thrust pushes it into ahead, or pulls it into astern. With it properly set up and new clutch linings in metric thicknesses the gap between ahead and astern is minimal. The slightest gearwheel movement will cause the whole thing to wind itself into gear without any input.

 

If the gear box is hard to move with the propshaft disconnected then the box will need dismantling to get at the bottom shaft bearing and .  It is not a difficult job and is described in the manual.  The bottom half of the box is quite heavy so have an extra Weetabix before starting.   Once off you can dismantle the back end to get at the shaft bearing and the rear thrust bearing, behind the astern cone.

 

Note that there are some boxes with no linings to the cones, but for now assume there are unless it is a very early engine.  There are various people who can reline the clutches, I last used Bremskerl  In Bath but also in other places. Or look in a vintage motor cycle mag for clutch recliners.  The original linings contained asbestos so some places will want any linings removed ( drill the rivets out)   before they will touch them. Remind whoever you pick  these are oil wet cones, not dry ones.

N

 

[darren620]

10 minutes ago, BEngo said:

Can you easily disconnect the prop shaft from the gearbox?  If so do, and then try a gear change. 

 

The whole prop shaft should slide back and forward  as the gear is changed. Disconnecting it will tell you whether it is the box, or the shaft that is not moving freely.

 

If the box is free investigate the shaft.  It may have a plummer block that wants greasing and/or the stern tube and gland need an investigate.

 

Also check the alignment. It needs to be accurate or the prop thrust will shove the box shaft off-centre.

 

I would incline toward it being a shaft problem, because the box is designed so that the prop thrust pushes it into ahead, or pulls it into astern. With it properly set up and new clutch linings in metric thicknesses the gap between ahead and astern is minimal. The slightest gearwheel movement will cause the whole thing to wind itself into gear without any input.

 

If the gear box is hard to move with the propshaft disconnected then the box will need dismantling to get at the bottom shaft bearing and .  It is not a difficult job and is described in the manual.  The bottom half of the box is quite heavy so have an extra Weetabix before starting.   Once off you can dismantle the back end to get at the shaft bearing and the rear thrust bearing, behind the astern cone.

 

Note that there are some boxes with no linings to the cones, but for now assume there are unless it is a very early engine.  There are various people who can reline the clutches, I last used Bremskerl  In Bath but also in other places. Or look in a vintage motor cycle mag for clutch recliners.  The original linings contained asbestos so some places will want any linings removed ( drill the rivets out)   before they will touch them. Remind whoever you pick  these are oil wet cones, not dry ones.

N

 

many thanks for all this info. 

 

reading through though. are you saying you think i should replace the clutch plates ( mostly because no oil/oil change for 10-15 years we can be certain they are toast ) and then the difficulty in moving between gears and neutral is likely an alignment problem. 

 

ive taken a picture of whats behind the box and then to the shafts heading back. is the plummer block the one to the right? thats definately had grease in its nipple. far too much. ( my fault ) the excess being ejected slowly. and being wiped up. 

 

i'm guessing the part to the right is a clamp i can undo and then remove in order to check how the gears will select in and out. if I miracle of miracles ) it does get easier i guess i am lifting floorboards and looking for bearing blocks to loosen and adjust?

 

thanks again. 

 

 

[Eeyore]

The brassy coloured lump to the right appears to be the freewheel for the hand start chain?

The bit in the middle of the picture is new to me.

Any plumber block (shaft bearing) is out of shot to the left.

Edited August 26, 2023 by Eeyore

[MtB]

24 minutes ago, Eeyore said:

The brassy coloured lump to the right appears to be the freewheel for the hand start chain?

 

 

 

That's the gear change linkage. There is no hand start chain, the hand start is the handle on the back of the gearbox. Visible in the same photo! 

 

 

[Bee]

Personally I would check that as Bengo says the whole shaft is free to slide forwards and backwards . You never know but some bright spark might have tightened a grub screw somewhere and the shaft is now fixed or nearly so......

[magnetman]

Yes because it has cone clutches. 

 

I once had a go on a narrow boat with a J2 and it had a tendency to pull itself out of gear when in ahead. I think it is to do with prop size and excessively free movement of the prop shaft. The owner had a weight hung on the gearchange wheel to discourage the effect. 

 

Yours sounds like the opposite problem Either an overtightened gland or possibly a bearing with grub screw as suggested already. 

 

Hopefully it is one of these and you can sort it out. 

 

 

 

[Tony Brooks]

35 minutes ago, magnetman said:

Yes because it has cone clutches. 

 

I once had a go on a narrow boat with a J2 and it had a tendency to pull itself out of gear when in ahead. I think it is to do with prop size and excessively free movement of the prop shaft. The owner had a weight hung on the gearchange wheel to discourage the effect. 

 

Yours sounds like the opposite problem Either an overtightened gland or possibly a bearing with grub screw as suggested already. 

 

Hopefully it is one of these and you can sort it out. 

 

 

Possibly even a badly worn shaft under the gland so the packing is restricting its movement.

[magnetman]

Yes maybe the shaft or stern tube liner is worn and someone at some point thought a good way to stop the water getting in was to tighten up the gland. 

 

I suppose the question 'is there a drip from the stern tube?' is worth asking. 

 

 

Also has the boat been moored and unused for a long time. 

 

I have tightened the stern tube gland right up on one of my boats which does not have the engine running much at all lately. It stops the water coming in and as it is on the River it also stops the prop freewheeling when the flow speeds up. I had it here all last winter and the prop didn't move. 

 

Of course when I start using the engine again I will loosen it orf.

 

 

 

 

[BEngo]

The bronze object with the  chain is called  the clutch thrust box.  Inside it is a ball bearing and a  fearsomely coarse square thread.  The grease nipple lubricates that, and the grease also acts as an oil seal.  As it is rotated by the chain and gear change  wheel it moves along the square thread, dragging the internal double male  cone clutch backwards or forwards, so changing gear. 

 

The piece behind it is a coupling connecting the gearbox output shaft to the intermediate shaft. It is not like anything I have seen before but appears to be held by the bolts, so I would undo them and see what happens.  It may be some sort of taper lock device.  It is certainly not a standard Kelvin muff coupling.  The gearbox output shaft is round.  No splines, no key ways.

 

As far as the clutch linings go I would leave well alone until either:

 

You have to take the box apart to see why it is still stiff, or for some other reason, or

The clutch slips while in ahead or astern,or

You cannot get it out of gear.

 

The rest of the info was simply a reply to your questions about where to go to get the clutches re-lined. I rather doubt the linings ( if there are any) are toast. 

 

In the pic, There are two pipes that are close to the coupling, between the flanges.  One goes down from an elbow on the port side and the other is a Tee-piece  going under from the stbd side.  Are these two pipes clear of the coupling at all times?  If they rub anywhere they will hinder the gear change.

 

[Tracy D'arth]

There was oil, albeit dirty, so it was not devoid of lubrication. I have seen worse on boxes that still work fine.

I would not worry about the cone clutch linings ( if indeed it has linings ) and look elsewhere for the problem, i.e. the shaft movement.

[Bod]

Question more for the experts.

Seeing the quantity of sludge, will the new oil soften the remaining sludge?

To the point of frequent changes, cleaning the internals of the box?

 

Bod.

[Eeyore]

3 hours ago, MtB said:

 

 

That's the gear change linkage. There is no hand start chain, the hand start is the handle on the back of the gearbox. Visible in the same photo! 

 

 

School day.

[BEngo]

1 hour ago, Bod said:

Question more for the experts.

Seeing the quantity of sludge, will the new oil soften the remaining sludge?

To the point of frequent changes, cleaning the internals of the box?

 

Bod.

Once we have got to the cause of the stiffness and if the box has not needed to be dismantled  it will probably be time to fill the box with paraffin and leave it standing for a while then drain well and refill with fresh oil.

Until then it wont come to any harm with clean oil in there.

[darren620]

MANY thanks to all for your input. 

i'll try to answer points here. 

 

no-one has been near this boat/engine with a set of spanners in the last 10-15 years. i'm the first and its a steep learning curve

 

i dont think the WHOLE shaft moves left/right. but i will check. i will lift back cabin boards and check for bearing blocks and grease nipples. 

 

the stern gland drips like a sieve. repacking is on my list

 

the idea for parrafin in the box is definately going on the list. a very similar tale became the injection regulator. ( and whaddya know it now ticks over sweet )

 

all the questions and points about things fouling the movement. ----- nothing has changed on this boat for 15 years + it used to be 100% a dream to pilot. in and out of gears like a dream. slowly over the last 15 ish. the only time its moved is once or twice a year. with a long slow decline in ease of use. its main problem in my humble opinion is a complete lack of basic maintenance.  

THANKYOU again all for your time and pointers. 

 

 

15 hours ago, BEngo said:

The bronze object with the  chain is called  the clutch thrust box.  Inside it is a ball bearing and a  fearsomely coarse square thread.  The grease nipple lubricates that, and the grease also acts as an oil seal.  As it is rotated by the chain and gear change  wheel it moves along the square thread, dragging the internal double male  cone clutch backwards or forwards, so changing gear. 

 

The piece behind it is a coupling connecting the gearbox output shaft to the intermediate shaft. It is not like anything I have seen before but appears to be held by the bolts, so I would undo them and see what happens.  It may be some sort of taper lock device.  It is certainly not a standard Kelvin muff coupling.  The gearbox output shaft is round.  No splines, no key ways.

 

i'll see about taking that "odd" coupling off once i have lifted the rear cabin board and checked for how it all works

 

15 hours ago, BEngo said:

As far as the clutch linings go I would leave well alone until either:

 

You have to take the box apart to see why it is still stiff, or for some other reason, or

The clutch slips while in ahead or astern,or

You cannot get it out of gear.

 

ok. i'll leave well alone and concentrate on checking the movement of the shaft. do you think it should all move? i'm not on the boat right now but i will check all that. 

 

 

15 hours ago, BEngo said:

 

The rest of the info was simply a reply to your questions about where to go to get the clutches re-lined. I rather doubt the linings ( if there are any) are toast. 

 

yes they are definately clear. all part of the cooling system ( i think ) 

15 hours ago, BEngo said:

 

In the pic, There are two pipes that are close to the coupling, between the flanges.  One goes down from an elbow on the port side and the other is a Tee-piece  going under from the stbd side.  Are these two pipes clear of the coupling at all times?  If they rub anywhere they will hinder the gear change.

 

 

[MtB]

10 minutes ago, darren620 said:

i dont think the WHOLE shaft moves left/right.

 

That's the problem then. The propshaft being free to slide back and forth through the stern gland is fundamental to the design of the gearbox.

 

I think mine used to move about an inch back and forth between ahead and astern, but I can't clearly remember. 

 

 

[darren620]

7 minutes ago, MtB said:

 

That's the problem then. The propshaft being free to slide back and forth through the stern gland is fundamental to the design of the gearbox.

 

 

ok, thanks. thats given me a complete direction and path to go down. rear cabin floor boards coming up soon. it seems i'm gonna find some proper gunged up bearring blocks and utterly empty grease niples. 

 

i think i should have mentioned also. 

 

on the trip back after i swaped the 30ml of sludge for 750ml of oil. there was a tendancy for the boat to not hold in forward gear.  ( i saw previous note about a weight on the gear wheel )

do we think this also likely related ?

[dave moore]

The prop shaft on our J3 used to move 3/4” when going from forward to reverse. We had to experiment with sprockets to achieve an easy change, about 4 turns from ahead to astern.

[BEngo]

1 hour ago, darren620 said:

 

on the trip back after i swaped the 30ml of sludge for 750ml of oil. there was a tendancy for the boat to not hold in forward gear.  ( i saw previous note about a weight on the gear wheel )

The gearbox is designed to accept the propellor thrust.  That is how it is meant to be held in gear. At the very front of the gearbox is a BIG deep groove ball bearing about 5 inches in diameter. The one I bought last year was over £300. ( Its Imperial,  top quality and was shipped from Germany.) There is another one at the back of the box.  The thrust comes along  the prop  shaft, into the ahead or astern cone  hrough the ball bearing, through the engine mounts  and pushes the boat along. If your shaft is set up properly it will not come out of gear. It is perfectly normal for the gear wheel to rotate about a quarter turn back all by itself, once the box has been wound into gear.  This takes  the clutch thrust box bearing load off.

 

Hanging a weight on the gear wheel is but a bodge.  It does not do the clutch thrust box, or its internal bearing any good.

 

The gearbox has evidently been neglected.  What is the state of the engine oil and crankcase?  If you have not looked inside  recently I suggest you take off a convenient side door and have a good look. You can take the doors off without difficulty and the oil level is below the bottom edge.

1 hour ago, dave moore said:

The prop shaft on our J3 used to move 3/4” when going from forward to reverse. We had to experiment with sprockets to achieve an easy change, about 4 turns from ahead to astern.

That is about typical for fairly new linings. It depends on the thickness of the gasket at the front of the gearbox and on the thickness of the linings. It  gets larger as the linings wear.

 

The clutch thrust box thread is 2 tpi IIRC so a new box will be a little less than half a turn each way on the  big bronze  wheel that is on the box.

 

I tried a direct drive from the gear wheel to the thrust box, but a 4 inch gear wheel wasn't man enough  so we now have about a 3:1 reduction and an  ahead-to-astern range of about 2 turns

 

N

[darren620]

8 hours ago, BEngo said:

The gearbox has evidently been neglected.  What is the state of the engine oil and crankcase?  If you have not looked inside  recently I suggest you take off a convenient side door and have a good look. You can take the doors off without difficulty and the oil level is below the bottom edge.

 

indeed. i thought this as soon as i was reading the comments you made about the lozenge shaped plates. the paint on those made it abundantly clear no-one had been in there in a long time. and of course the evidence was clear. i'll get that flushed soon with parafin or diesel. and get the level sorted with the proper oil again. the boat isnt moving again this year at least. so i'll start with the tasks. 

 

seemingly the primary task is to get the rear boards up and look for bearing blocks and grease points that probably havnt even seen light in years nevermind grease. 

 

the engine oil was changed within a year or few. there is a dipstick and the oil on it looks surprisingly clean. not at all black. and slightly above the top level ( i attributed the exhaust smoke could be partly to blame. the extraction pump on the other side is all painted and never used. the last oil change seemingly used a vacuum pump down the dipstick. the rocker cover oilers had never failed to be used so the extra oil in the sump would most likely ( i thought ) been the gathering of that. an oil change is on the winter list. 

[Tracy D'arth]

A few years ago I serviced the engine in an old boat from the '70s.

The engine oil was black and sticky. The PRM gearbox was the old hydraulic, can't remember the number, with an oil filter on top.

The filter was very rusty all over and very firmly stuck, it had to be ripped off with a Stillson wrench.

The oil would not come out with the Pela pump no matter how hard I pumped it up.

The drain plug was incredibly tight but eventually it came out and a blob of filthy oil oozed out. #

Inspecting the magnetic plug revealed a lot of fine metal particles and unmarked flats and corners. The suspicion was that it had never been out from new, in fact, that the gearbox oil and filter had probably never been changed.

The gearbox and cooler were washed out with diesel and refilled with oil.

PRM now do not advise using an oil filter and used to market  a kit to blank it off. I fitted a new filter as the kit was not available.

The gearbox worked just fine and as far as I know is still OK. A testament to PRM's engineering.

 

[BEngo]

I find the Kelvin sump emptying pump is more of a device for spreading oil around the engine ole than anything else. It certainly doesn't get all the oil out so a Pela or similar down the dipstick tube will be just as effective. Then follow up with an old  tablespoon through a handy door to get the last bit, and the  sludge.

 

N

[MtB]

1 hour ago, BEngo said:

I find the Kelvin sump emptying pump is more of a device for spreading oil around the engine ole than anything else. It certainly doesn't get all the oil out so a Pela or similar down the dipstick tube will be just as effective. Then follow up with an old  tablespoon through a handy door to get the last bit, and the  sludge.

 

Given one always ends up taking a door off anyway, I just short-cut to bailing it out with a cup, then loads of Blitz kitchen roll to get the last half an inch (and any sludge) out. 

P.S. I keep meaning to try using my big silver plated soup ladle!