Unpleasant discovery changing gearbox oil

[Ruffles]

MD2030B with MS2A-D gearbox to shaft.
Gearbox oil was decidedly grey. In the past the oil has come out as new so clearly there's a major issue. Horrible.
Presumably this is linked to the nasty rumbling noise we've been getting at low revs.
Is this the gearbox cooler leaking? Have left a sample to settle overnight.
It went off to a dealer to fix the rumble. They replaced bits for £££. No change.
Time to replace the engine? < 900 hours but 20+ years old.

 

[Boater Sam]

MD2030B with MS2A-D gearbox to shaft.

Is this the gearbox cooler leaking?

Almost certainly unless it has been under water.

 

[Refueler]

Gearbox oil can become grey to white - depending on how much water gets in ... the oil emulsifies ... and the water will not drop out ...

The harsh sound .. know it well ... I had similar when my oil cooler tubes gave out on mine ... different box on a Perkins - PRM - but same result.

I Pela'd out what I could ... looked like yoghurt .... removed oil cooler - gave it to a pal ... who rebuilt it. He remarked that the original was in his opinion not very good ... he revised the tube diameters and number of them ... I fitted this ... then put in very light oil - ran it for a bit to flush round ... Pela'd out this ... another fill of light oil and flush ... Pela'd out and then filled with usual oil.
That box is still going good 14yrs later ....

The box and engine ? Antique !!

 

[Refueler]

Why do you think to replace engine ? 900 hrs ?? 20yrs old ? Engine's barely run in !!

If its starting and running well ... why ??

 

[Boater Sam]

Fix/replace the heat exchanger.
Wash the box out twice with diesel, running it for 2 minutes only at tick-over on each fill. Let it drain out completely through the drain plug.
Fill with fresh oil and do an oil change after 10 to 30 hours and the box will be fine for years.

 

[Refueler]

Fix/replace the heat exchanger.
Wash the box out twice with diesel, running it for 2 minutes only at tick-over on each fill. Let it drain out completely through the drain plug.
Fill with fresh oil and do an oil change after 10 to 30 hours and the box will be fine for years.

You can use the cheapest supermarket thinnest oil you can find ...

Using Diesel fuel is OK - if you want to clean stuff .. but its what we term a 'Dry' product ... in that it has extremely limited lubrication qualities and if not flushed out - lead to 'initial dry' running.
I do suggest cheapest crap oil you can find ...

 

[ducked]

MD2030B with MS2A-D gearbox to shaft.
Gearbox oil was decidedly grey. In the past the oil has come out as new so clearly there's a major issue. Horrible.

Gearbox oil from my 1800 Marina settled out (in a coke bottle) as alternate bands of copper and black iron, and I THINK it had the same number of bands as it had synchromesh rings.

Of course AFAICT this cannot make any sense other than as an odd coincidence, and has no marine relevance, but I thought it was perhaps peculiar enough to be worth a mention.

Changed gear smoothly, and continued to do so for a few years, until a spring hangar broke and I sold it.

 

[Ruffles]

Thanks all.
I have flushed with a thinner oil. This came out much the same.
Left it to settle out in a jug overnight but, though still opaque, no water in the bottom.
It does sound different after the oil change so I'm sure the gearbox is the source of the noise.
It's a question of confidence really. I need to know what is up with it.
Boat is in Haslar for the Winter. Any recommendations for someone to check it out?
Would rather not use the VP people I sent it to. Am sure they replaced bits that needed replacing. But they did visit the boat to diagnose and what they replaced did not sort it out.

 

[Refueler]

If you are getting discoloured oil after only a shortish run - then suspect the oil cooler - which is water cooled ...

I would be inclined to remove the Oil Cooler and then pressure test the tubes ..... (no need to pressure test general casing - as that would be evident when used on the box).