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Water in the gearbox.


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24 minutes ago, system 4-50 said:

The oil cooler on my PRM 150 failed and the oil in the gearbox turned to an emulsion.  Oil also appeared in the coolant.

I have heard of that happening. I am puzzled as to how the mix ends up in the bilge, unless the heat exchanger is leaking outwardly too perhaps?

Edited by Guest
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I daressay these boxes were designed long before sympathetic oil was introduced, so PRM stick to the oil they know and tested them with, ie mineral engine oil.  The oil pump retaining bolts can often leak oil too on these boxes. The pump is the round thing on the back of the box next to the output propshaft half coupling. A couple of the threaded bolt holes go right through into the oil space inside. They have wee copper washers under their heads as seals. These bolts often go a bit slack as the soft copper washers tend to give a bit.

Edited by bizzard
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39 minutes ago, catweasel said:

I have heard of that happening. I am puzzled as to how the mix ends up in the bilge, unless the heat exchanger is leaking outwardly too perhaps?

It was a while ago and I may not be remembering the detail correctly but I think in my case a tiny amount of emulsion appeared around the filler bolt (?) or similar - is there a breather? I don't remember anything in the bilge.

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On 27/07/2018 at 19:20, catweasel said:

Here we go:

 

http://www.prm-newage.com/help-centre-marine

 

Q: WHAT OIL DOES MY GEARBOX TAKE?

A: A mechanical gearbox (PRM 60, 80, 90, 120 or 125) must use automatic transmission fluid (ATF) Dextron II or III

All hydraulic gearboxes must use mineral 15W40 (not synthetic) (my bold and underline)

 

 


I think for the hydraulic boxes "must use 15W/40" is a bit OTT.  Not advice I have seen from them before.  If you contact them they will generally say "whatever you put in your engine - if it is OK for that it is certainly OK for our gearboxes".  So it shouldn't matter whether it is 10W/40, 15W/40, 20W/50 or straight SAE 30 - any should be OK.

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54 minutes ago, catweasel said:

I have heard of that happening. I am puzzled as to how the mix ends up in the bilge, unless the heat exchanger is leaking outwardly too perhaps?

I reckon it works both ways. Oil contaminates the coolant when the engines running because the oil pressure is higher than the coolant pressure. After a run and the engines switched off the oil pressure will fade  away quickly whilst the coolant pressure  remains and will take a while to fade, it then contaminates the oil.

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41 minutes ago, system 4-50 said:

It was a while ago and I may not be remembering the detail correctly but I think in my case a tiny amount of emulsion appeared around the filler bolt (?) or similar - is there a breather? I don't remember anything in the bilge.

That certainly makes sense.

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35 minutes ago, alan_fincher said:


I think for the hydraulic boxes "must use 15W/40" is a bit OTT.  Not advice I have seen from them before.  If you contact them they will generally say "whatever you put in your engine - if it is OK for that it is certainly OK for our gearboxes".  So it shouldn't matter whether it is 10W/40, 15W/40, 20W/50 or straight SAE 30 - any should be OK.

Strange really that they should say one thing in the manual, then say something else. I can't find the paperwork that came with mine, probably lost when we moved aboard, but I distinctly remember the "no synthetic" thing, and vaguely about different grades of oil for different operating conditions.  Mine gets Comma 15/40 mineral as per the engine. It has been in nearly two years and owing to health issues has hardly been used yet! 

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I think you will  find that all return oil from the direction valve in neutral or the system pressure relief valve when in drive passes through the cooler then back to the gearbox sump. The hydraulic pump is always adding heat to the oil so long periods of running in neutral will overheat the oil without a cooler in circuit. The clutch plates in the 150 are flat sintered metal . If you leave any moisture in the oil the bearings will be the the first to fail with a high risk of the gears failing due to miinute pockets of water not providing lubrication under load. After water ingress change the oil several times using the bottom drain plug. I know this as I had a box fail after the same problem you have had, the shaft oil seals are sometimes single lip facing the oil but not good enough to stop water ingress when submerged, also the O ring on the valve can dothe same plus the breather and filler if you had a lot of water in.

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5 minutes ago, adrianh said:

I think you will  find that all return oil from the direction valve in neutral or the system pressure relief valve when in drive passes through the cooler then back to the gearbox sump. The hydraulic pump is always adding heat to the oil so long periods of running in neutral will overheat the oil without a cooler in circuit. The clutch plates in the 150 are flat sintered metal . If you leave any moisture in the oil the bearings will be the the first to fail with a high risk of the gears failing due to miinute pockets of water not providing lubrication under load. After water ingress change the oil several times using the bottom drain plug. I know this as I had a box fail after the same problem you have had, the shaft oil seals are sometimes single lip facing the oil but not good enough to stop water ingress when submerged, also the O ring on the valve can dothe same plus the breather and filler if you had a lot of water in.

That's what I figured, the oil has to have a cooler in circuit at all times.

The breather is a small open fitting on the top of the box with a crimped on loose steel thimble cap.

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I've cleard all the contaminated oil and flushed several times with new oil. There does not appear to be any leakage of oil anywhere and no water ingress. I presume therefore that when the water got in the bilge there must be a breather but cannot find it. Anyway all seems well and I;m up and running again. Thanks for the advice and the technological explanations which were way above my head.

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