Gearbox oil change (PRM150)

[robtheplod]

Hi All

 

I changed this today since I've no record when it was last done. The old oil was grey like - very different to the engine - is this usual?

 

ta

rob

[Melita]

The PRM 150 should use the same oil as you use in the engine. Sounds like what you took out could have been in there for a very long time and had degraded.

[robtheplod]

10 minutes ago, Kendorr said:

The PRM 150 should use the same oil as you use in the engine. Sounds like what you took out could have been in there for a very long time and had degraded.

Thanks for your speedy reply... so normally it would come out same sort of colour as the engine oil?

[alan_fincher]

9 minutes ago, robtheplod said:

Thanks for your speedy reply... so normally it would come out same sort of colour as the engine oil?

No,

Normally it comes out looking much like new oil, and still golden colour.

The engine oil goes black because of combustion.  There should be no combustion in your gearbox!

Any chance it had water in it?  If you have a gearbox oil cooler that's on the engine cooling circuit, a leak of water into the gearbox oil is at least a theoretical possibility.

Edited November 17, 2019 by alan_fincher

[Graham and Jo]

7 minutes ago, robtheplod said:

Thanks for your speedy reply... so normally it would come out same sort of colour as the engine oil?

Mine comes out pretty much the colour it went in. There is no carbon muck to make it dark like used engine oil. Cheers Graham

[Tony Brooks]

Grey could be a way of describing the whitening effect of emulsification (water) but it could also be the result of  wearing clutch material. Drain, refill, run for half an hour in all gears plus neutral. drain, refill and see how it goes.

[robtheplod]

11 minutes ago, Tony Brooks said:

Grey could be a way of describing the whitening effect of emulsification (water) but it could also be the result of  wearing clutch material. Drain, refill, run for half an hour in all gears plus neutral. drain, refill and see how it goes.

Thanks, will definately do this when I get back to the boat!

[Melita]

Yep, as all have said, oil looks pretty much the same as when it went in. With my first PRM 150 I did leave the oil in too long because it 'looked okay'!! New boat, new engine and gearbox, oils changed every year.

[tizzy]

Can anyone enlighten me please. Why is it that gearbox oil needs changing. What happens in a gearbox to cause it to deteriorate. As mentioned above there is no combustion process to contaminate it so surely it should last a very long time.

[Tony Brooks]

12 hours ago, tizzy said:

Can anyone enlighten me please. Why is it that gearbox oil needs changing. What happens in a gearbox to cause it to deteriorate. As mentioned above there is no combustion process to contaminate it so surely it should last a very long time.

Contamination by clutch debris and gear tooth/bearing wear. Plus it will oxidise to as it ages. I personally think it will last far longer than a year, especially if you have a magnetic drain plug, but it is so easy to change its not worth no doing.

[tizzy]

Many thanks for the reply Tony. Very interesting.

 

I have never changed the oil in our PRM but whenever I check the dip it is clear. We have had the boat for 5 years so I guess it is worth doing. I was looking at recommendations for cars and they are usually about 60000 miles which probably equates to something like 1500 hours on a boat which for us is 4 to 5 years (leisure boaters). Plus the gearbox on a car must be working far harder than a boat where once forward gear is engaged it chugs away uninterrupted.

[robtheplod]

28 minutes ago, tizzy said:

Many thanks for the reply Tony. Very interesting.

 

I have never changed the oil in our PRM but whenever I check the dip it is clear. We have had the boat for 5 years so I guess it is worth doing. I was looking at recommendations for cars and they are usually about 60000 miles which probably equates to something like 1500 hours on a boat which for us is 4 to 5 years (leisure boaters). Plus the gearbox on a car must be working far harder than a boat where once forward gear is engaged it chugs away uninterrupted.

Interestingly when I checked the dipstick it was always clear, but not when I changed it.....

[bizzard]

1 minute ago, robtheplod said:

Interestingly when I checked the dipstick it was always clear, but not when I changed it.....

It wasn't colour fast like cheap socks and woolies.

[Sea Dog]

1 hour ago, tizzy said:

I have never changed the oil in our PRM but whenever I check the dip it is clear. We have had the boat for 5 years so I guess it is worth doing. I was looking at recommendations for cars and they are usually about 60000 miles which probably equates to something like 1500 hours on a boat which for us is 4 to 5 years (leisure boaters). Plus the gearbox on a car must be working far harder than a boat where once forward gear is engaged it chugs away uninterrupted.

Deciding when to change your gearbox oil based on a guestimate of an extrapolation from a typical car is quite a stretch.  I'd say you're way out - why not check in your engine/gearbox manual, or at least something remotely comparable?

 

If it helps, mine (Beta 43 and PRM150) tells me to change the gearbox oil when the engine oil is changed - every year or 250 running hours, whichever is first. The gearbox oil always looks clean - so much so you can hardly see it on the dipstick!

 

The oil recommendation is to use the same multigrade as for the engine. Car gearboxes don't usually use that oil, but neither do cars usually use  hydraulic gearboxes designed for a boat!

 

 Oil is much cheaper than a new gearbox -  change it as recommended.  

 

[Ex Brummie]

The dipstick oil always looks clean, but when you drain it, it is amazing how dirty the oil that doesn't touch the dipstick really gets. As Sea Dog says, oil is cheaper than gearboxes.

[robtheplod]

When filling the PRM150 with new oil, is it like the engine whereby you then run it and have to top up as oil gets taken around the system (filters etc) or is it pretty much a pool that doesn't change?

[Melita]

30 minutes ago, robtheplod said:

When filling the PRM150 with new oil, is it like the engine whereby you then run it and have to top up as oil gets taken around the system (filters etc) or is it pretty much a pool that doesn't change?

It's a pool that doesn't change.

I have made a dipstick from a piece of dowel because I find it very difficult to see the level on the metal one, so I use the piece of dowel to check the level, then screw the proper one in. I was also told that if you drop the dipstick in but don't screw it in for checking, the oil should come up to the lower point, once screwed in properly it will be at, or very close, to the upper point.