JP2 Reduction box

[monkeyhanger]

When I was out cruising this summer, I noticed that oil from within my 2:1 reduction box was being forced out of the dipstick hole. Not a great deal, but enough to cause me to have to wipe it down at the end of a days travelling. I then had to check and top up the oil regularly, which is something I normally would expect to do perhaps twice a year. In fact I had to buy a new bottle of EP80, which came as a surprise, as the previous bottle only lasted 20 years!

I came to the conclusion that the reduction box was becoming pressurised in some way, so I fitted a fuel tank breather instead of the normal filler plug, and problem solved, no more leak. Except......... I am now aware of the sounds of the reduction box as I travel along, a sort of groaning noise, which to my mind would seem to indicate wear of some sort. I rebuilt the box 20 years ago, with new bearings and gears, as I had similar symptoms, but with much louder groaning noise.

Obviously something is wrong, but what? I hope it's only a bearing or similar as my wallet still hurts from the price of the new gearset all those years ago.

Can I expect a noise from the box? If so, I can refit the filler plug and the noise will go away-- but the oil loss will probably return.

If anyone has any thoughts I'd like to hear them. Jack

[frangar]

My box has a raised filler tube with a brass nut that has a cross drilled hole in it….as per the parts list I believe. Presumably this acts as a raised vent.

 

Mine also makes a whiring noise but its not getting any worse and I had it rebuilt about 1000 hours ago by Llewelins Gears who seem to know what they are doing…at the time they replaced the bearings….i too had a gear set replaced many years previously but they were deemed ok the last time.

 

it may be that the seal is going on the shaft and its getting pressure from the reversing box/crankcase. its also possible that the gear oil is tracking back into the engine….another reason I run my box on straight SAE 50 again as per Lister Manual…so there aren't any EP additives going into the engine oil.

 

I did notice a bit of seepage this year around the base of the filler tube and dipstick but we were mainly on deep water with the engine revving harder than on canals.

 

Have you checked for any leaks either round the output shaft or drain plug?

 

Cheers

 

Gareth

[monkeyhanger]

My box has a raised filler tube with a brass nut that has a cross drilled hole in it….as per the parts list I believe. Presumably this acts as a raised vent.

 

Mine also makes a whiring noise but its not getting any worse and I had it rebuilt about 1000 hours ago by Llewelins Gears who seem to know what they are doing…at the time they replaced the bearings….i too had a gear set replaced many years previously but they were deemed ok the last time.

 

it may be that the seal is going on the shaft and its getting pressure from the reversing box/crankcase. its also possible that the gear oil is tracking back into the engine….another reason I run my box on straight SAE 50 again as per Lister Manual…so there aren't any EP additives going into the engine oil.

 

I did notice a bit of seepage this year around the base of the filler tube and dipstick but we were mainly on deep water with the engine revving harder than on canals.

 

Have you checked for any leaks either round the output shaft or drain plug?

 

Cheers

 

Gareth

Haven't noticed any leaks,other than the one at the dipstick, but I'll check again. Once I fitted the breather to the filler tube the oil level remained pretty constant. I wouldn't have thought that any pressurisation would come from the gearbox, as that is connected to the crankcase which has a breather fitted.

Maybe I need to take the reduction box apart to have a check just in case.

[frangar]

Personally I would just fit a cross drilled plug on the breather tube rather than strip the box! Its all mine has and seems to work well.

 

Is the noise better or worse in reverse?

 

Might be an idea just to check that the breather on the crankcase is clear….if its blocked it might explain it.

 

I seem to find that you can pick up on every strange noise from a JP (or indeed other vintage engines i guess!) Mine seemed to make more odd noises just as I went onto the tidal Trent!

 

Cheers

 

Gareth

[by'eck]

Personally I would just fit a cross drilled plug on the breather tube rather than strip the box! Its all mine has and seems to work well.

 

Is the noise better or worse in reverse?

 

Might be an idea just to check that the breather on the crankcase is clear….if its blocked it might explain it.

 

I seem to find that you can pick up on every strange noise from a JP (or indeed other vintage engines i guess!) Mine seemed to make more odd noises just as I went onto the tidal Trent!

 

Cheers

 

Gareth

 

Yes I've noticed that, and when entering long tunnels as well

[monkeyhanger]

Personally I would just fit a cross drilled plug on the breather tube rather than strip the box! Its all mine has and seems to work well.

 

Is the noise better or worse in reverse?

 

Might be an idea just to check that the breather on the crankcase is clear….if its blocked it might explain it.

 

I seem to find that you can pick up on every strange noise from a JP (or indeed other vintage engines i guess!) Mine seemed to make more odd noises just as I went onto the tidal Trent!

 

Cheers

 

Gareth

Fitting a drilled plug is not a bad idea. It's certainly worth a try first anyway.

I can't hear if the noise is any different when in reverse. It's a Blackstone box, so it's difficult to hear anything in reverse!

Good idea about checking the breather, too, but if I remember correctly, there's actually very little in them so I wouldn't have thought they'd clog easily.

And yes, I know what you mean about strange noises. I have a clicking from my water pump which only manifests itself when it sees fit. "Starman" had a similar problem with his JP3, and I suggested it could be his water pump. Judging by the fact that he hasn't been back on here asking about it, it must have fixed itself. Jack

Edited October 22, 2014 by monkeyhanger

[frangar]

Fitting a drilled plug is not a bad idea. It's certainly worth a try first anyway.

I can't hear if the noise is any different when in reverse. It's a Blackstone box, so it's difficult to hear anything in reverse!

Good idea about checking the breather, too, but if I remember correctly, there's actually very little in them so I wouldn't have thought they'd clog easily.

And yes, I know what you mean about strange noises. I have a clicking from my water pump which only manifests itself when it sees fit. "Starman" had a similar problem with his JP3, and I suggested it could be his water pump. Judging by the fact that he hasn't been back on here asking about it, it must have fixed itself. Jack

The breather is really simple....just a cover over a hole really!...but mine seems to collect fluff and crud that sits on the grease that falls off the grease nipple for the rocket shaft....worth a look though.

 

I agree about the noise from the box in reverse! Take heart that at least you have a proper marine JP....far superior to those with modern reversing boxes!

 

I think at worst the noise might be a bearing but it might also be a bearing on the prop shaft and the noise may be travelling up the shaft...personally I would use a drilled plug and see how that goes....just see if the noise gets worse. Also check the colour of the oil when you change it....if a bearing is wearing it will show up with "glitter" in the oil.

 

My brass plug just has one hole of about 2.5mm drilled through it.

 

Edited to add

 

I've now cleaned the breather hole in the brass nut out....whoops!

 

Here's some pics! Hopefully....

Edited October 22, 2014 by frangar

[monkeyhanger]

The breather is really simple....just a cover over a hole really!...but mine seems to collect fluff and crud that sits on the grease that falls off the grease nipple for the rocket shaft....worth a look though.

 

I agree about the noise from the box in reverse! Take heart that at least you have a proper marine JP....far superior to those with modern reversing boxes!

 

I think at worst the noise might be a bearing but it might also be a bearing on the prop shaft and the noise may be travelling up the shaft...personally I would use a drilled plug and see how that goes....just see if the noise gets worse. Also check the colour of the oil when you change it....if a bearing is wearing it will show up with "glitter" in the oil.

 

My brass plug just has one hole of about 2.5mm drilled through it.

 

Edited to add

 

I've now cleaned the breather hole in the brass nut out....whoops!

 

Here's some pics! Hopefully....

Many thanks for your help on this one! My filler plug is a low profile steel one, with no (obvious)breather hole. I'll have to have a closer look next time I'm at the boat. Interesting that you mentioned changing the oil-- you know, I can't ever remember changing the oil in my reduction box! That will have to be high on the "to do" list. How often do you change the oil in yours?

[frangar]

I tend to change mine when I service the engine...which is once a year (450 hrs according to the manual!)

 

The reduction box doesn't take much oil....it just fills the ice cream tub that fits underneath it. I find it quite easy to overfill when replacing.

 

The part no for the plug is X99/5843 If that helps....might be worth asking MPS or Sleeman & Hawkin etc.

 

Cheers

 

Gareth