PRM 120 gearbox oil change

[RLWP]

1 hour ago, Chewbacka said:

Bits from the bearing surfaces? 

I don't think you'll be worried about debris on the drain plug if the ball races  are breaking up

[Chewbacka]

55 minutes ago, RLWP said:

I don't think you'll be worried about debris on the drain plug if the ball races  are breaking up

But if you can keep the tiny particles (raceway spalling etc) out of the bearings they will break up that bit slower.

[David Mack]

11 hours ago, RLWP said:

I wonder what it would collect? The cone clutch is made of bronze, as is the operating wedge

 

Richard

I've heard they fit a special bronze magnet to the PRM 120 drain plug. ☺️

[TNLI]

On 10/06/2018 at 22:20, RLWP said:

Well, one possibility is calling in an engineer because the gearbox slips

I was waiting for this post

General comment for all box lovers, READ THE OPERATORS OR MAINTENANCE MANUAL, do not guess which basic type of oil, or hydraulic fluid you need to use. The PRM 100 hydraulic box for example uses normal conventional engine oil. Using too thick an oil has a similar effect to overfilling the box, it can wear out the clutch plate due to too high a fluid or oil pressure.

  Using oil instead of hydraulic fluid, or other way round, can be real bad news even if it's the correct viscosity. Engine oil and hydraulic fluid contain completely different additives and that can damage the oil seals, or cause the clutch plate to slip if you use an oil in a hydraulic box. Hydraulic fluid does not contain detergents or molybdenum disulphide friction modifying additive.

  Also it's daft to comment on any forum if you have not checked the worlds most common, but least read booklet, the owners manual!

 

The step by step guide to dismantling a PRM 100 marine gearbox - Practical Boat Owner (pbo.co.uk)

 

100 & 175 & 250 man.pdf (prm-newage.com)

 

A now for something completely different, a final comment from the PBO PRM guide:

 

Speaking of which, don’t forget to fill up with oil again before you try the thing out. Notwithstanding that the PRM 100 and 140 et al are described as hydraulically operated gearboxes they use ordinary 15w40 engine oil (mineral, not synthetic). Do not use hydraulic fluid, which will give the box a sad case of palsy, but note that there are some mechanically operated PRM models that do use hydraulic fluid. Check the operating manual.

 

Edited January 18, 2022 by TNLI

[ditchcrawler]

I wonder if MichaelG is on the move yet?

[Tony Brooks]

6 minutes ago, ditchcrawler said:

I wonder if MichaelG is on the move yet?

 

I wonder why some feel it necessary to reopen a 3.5 year old topic and add nothing of any value or insight to that topic. In fact giving info for a hydraulic box when the topic was for a mechanical one seem more likely to confuse than enlighten. All the required information was provides years ago.

[Alan de Enfield]

1 minute ago, Tony Brooks said:

 

I wonder why some feel it necessary to reopen a 3.5 year old topic and add nothing of any value or insight to that topic. In fact giving info for a hydraulic box when the topic was for a mechanical one seem more likely to confuse than enlighten. All the required information was provides years ago.

 

It has become a proven fact on here that some / several posters do not read what the thread actually refers to, and in order to show their superior knowledge  just detail some totally unrelated information. Generally if someone asks a question it is because they are not knowlegable on the subject so irrelevant information makes it even worse.

[Tony Brooks]

11 minutes ago, Alan de Enfield said:

 

It has become a proven fact on here that some / several posters do not read what the thread actually refers to, and in order to show their superior knowledge  just detail some totally unrelated information. Generally if someone asks a question it is because they are not knowlegable on the subject so irrelevant information makes it even worse.

 

I agree 100%, but that some is a very small number, probably in low single figures. I make a distinction between those who try to help based on less experience and happily accept others input and those who seem to do it as routine and show those with experience just how little they really know. I have asked the mods to look at one particular poster but they seem happy to let the confusions continue.

 

i just hope I don't fall into that kind of thing too often.

[TNLI]

On 10/06/2018 at 21:28, MichaelG said:

Hi all, my boat is fitted with a PRM 120 gearbox circa 2006. I wonder if anyone who has one of these boxes could tell me what oil should be used. The information I have found on the web is a bit contradictory, some saying Automatic Transmission Fluid should be used, other sources saying ordinary mineral motor oil. I think the ambiguity may well be caused by the manufacturer changing its own advice over the years.

Also, silly question time, is changing the oil as simple as draining from the drain plug and refilling via the screw out dipstick hole?

 

Many thanks, Michael.

I suspect that most hydraulic boxes used for marine applications have a 2 way oil drain pump, rather than a simple drain plug, although some hydraulic boxes have a separate oil change pump.

 

Oddly enough the procedure for adding oil is not in the PRM gearbox manual, although there is a hint in one diagram that you use what I presume is the black dipstick cover, although I'm still trying to find out if it unscrews or just pulls out. In the old days there used to be a sticker or symbol on or right beside all fill points or dipsticks.

 

I know this is a moderately old thread, but starting new ones is bad news. Hijacking one without being able to fully delete the post is bad news. Deviating away from the subject seems to be common place in this forum, as does simple winging and whining on at other posters.

 

As for myself I'm rebuilding, upgrading and even painting a BMC 1500D with a PRM 100 box. Biggest job is definitely the paint. Most forum killer just have an armchair and no boat or barge.

 

On an oily note I did notice from reading the PRM series PDF that some of those top of the range boxes do not have an oil or hydraulic filter, like most of the early models. They just rely on a magnetic plug or some type, probably a bronze one. Oil analysis labs do accept the contents of a filter, or if it is a spin on type, the entire filter. If a box has a mag plug, you can drain some of the 200ml required for all the different tests, but would need to scrape the plug into the same used oil container for a sensible result. 

I've changed oil from Liqui Moly Super Nova 20W50 to 15W40 as I can't find the 20W50 at present. There is not much difference between the 2, same TBN so probably similar additives, and the viscosity is almost the same at normal temperatures. The reason for that is that the 20w50 is at the low end of the SAE group, and the two SAE figures are only for specific temperatures, The graph of actual kinematic viscosity vs temp is a curve, and that results in the 2 oils being closer than expected. If you do need to mix oils, they should be of the same basic type, so I would never mix a conventional oil with a full synthetic for example. The resulting interactions between the various additives would produce an unknown result that could damage the oil seals.-

Edited January 18, 2022 by TNLI

[Alan de Enfield]

17 minutes ago, TNLI said:

As for myself I'm rebuilding, upgrading and even painting a BMC 1500D with a PRM 100 box.

 

Surely a brush would be easier to use and would give a better finish.