loud clunk when gear engages?

[umpire111]

have an Isuzu Marine IM4LB33 engine with a Newage PRM 120D2 gearbox. The gear only engages at about 800rpm and then with a distinct clunk. Any idea why and who can rectify it?

[Lockie Junior]

PRM mechanical boxes always engage with a bit of a bang, its just how they are. The PRM box on the Lister in my cadet's launch definitely lets you know you're in gear!

 

As to the why, I'm sure someone with a more intimate knowledge of PRM boxes will be along shortly.

 

Regards,

Lockie.

[RLWP]

The clunk is common on the hydraulic boxes, a bit more unusual on the 120.

 

Is it the same in reverse, and what oil are you using?

 

Richard

[umpire111]

away from the boat at the moment so cannot answer re oil

but the owners manual states the gear should engage smoothly and without a clunk

[RLWP]

Check what oil, it should be ATF. And it should engage and lock easily. I m interested to see if it is the same in reverse as it could be something to do with the spiral in the centre

 

I think I put up a thread on the 120, not easy to find on a phone

 

Richard

[Richard10002]

Has it just started clunking, when it was smooth before. Or is it a new to you boat, which clunks when you didnt expect it to?

[umpire111]

just buying the boat and will not be back at it until Sunday 1st but will find out if it does it in reverse- grateful for all the responses- its in Wakefield- any idea of a place who may be able to look at it if it needs service/repair etc?

[Arphamoe]

We had a similar experience lately! A 'mild' clunk developed into a much more pronounced clunk on our Beta 38/PRM120 set-up. Then, when going through Hillmorton locks, the gearbox seized. Required replacement of gearbox and drive plate, which had been seriously deformed.

 

Thank heavens, (or deity of your choice!) for RCR who were magnificent, and were able to sort it for us. Silver membership dropped the bill of £1200 to £120!!

 

Hindsight tells us that we may have been able to avoid the stress by having the bits looked at as they developed, so be prepared to investigate further before final decision. Can't help as in Midlands, but there will be people locally who can advise

[Richard10002]

On a previous boat with a Hurth gearbox, I was told by the previous owner that ordinary engine oil was what he used in the gearbox. So that's what I did ..... and I got some serious clunking. A bit of proper research revealed that it should be a particular type of ATF. I suspect the previous owner had either never changed the oil, or had never had anything to do with changing it.

 

First thing I would do is change the oil, making sure I used the right stuff! I would also check the linkages.

 

After that I would have to hand over to an expert

[NBDensie]

We have an Isuzu 35 with a PRM120 gearbox. When we first bought the boat we found the starting clunk rather loud. After the idling speed was reduced to improve handling at tick-over we found it much less obtrusive.

[Chalky]

We've got an Isuzu IM4LM33 with the PRM120 mechanical gearbox. It has always gone clunk (actually more of a thud as the clutch engages) when going into and out of gear and has done so for the last 11 years. The gear box oil has been changed regularly (more frequently than PRM recommend). We've always used engine oil since that's what the manual recommends. Never tried ATF in it. I've always assumed that the clunk is normal since it's been like that from new.

Edited August 30, 2014 by Chalky

[umpire111]

strongly suspect that ordinary engine oil was used in the gearbox, the manual for the gearbox states to use API CC grade oil- is that the same at ATF?

[Tony Brooks]

strongly suspect that ordinary engine oil was used in the gearbox, the manual for the gearbox states to use API CC grade oil- is that the same at ATF?

 

No

 

PRM changed the oil specification maybe a year or two ago from engine oil to Automatic Transmission Fluid (ATF) for their mechanical boxes (NOT hydraulic ones).

[AndrewIC]

PRM changed the oil specification maybe a year or two ago from engine oil to Automatic Transmission Fluid (ATF) for their mechanical boxes (NOT hydraulic ones).

Out of curiosity, did they change anything in the gearboxes at the same time, or was the recommendation for ATF retrospective for existing boxes as well?

[Tony Brooks]

My understanding is that it covers all their mechanical boxes but why not ask PRM on Monday.

[RLWP]

My understanding is that it covers all their mechanical boxes but why not ask PRM on Monday.

 

Or read the manual on their website: http://www.prm-newage.com/media/uploads/5073d7f21d7d5.pdf

 

Page 7, 4.3 Approved oils Automatic Transmission Fluid (ATF)

 

Richard

[Chalky]

 

Or read the manual on their website: http://www.prm-newage.com/media/uploads/5073d7f21d7d5.pdf

 

Page 7, 4.3 Approved oils Automatic Transmission Fluid (ATF)

 

Richard

 

The manual I have that came with the engine/gearbox stated API cc-grade oil. It's due a change so I'd be interested in what PRM have to say. My father in law knows some of the older staff there (he was a gear cutter before he retired). I'll see if he knows any one who would know.

[RLWP]

I would be very interested if they recommended something other than what the latest manual says

 

Let us know what you find out

 

Richard

[Neil Smith]

I have just bought a new barrus shire fitted with a 120 prm and the book says ATF. the clonk I have been told will be worse if you don't wait until engine is at tick over before selecting forward or reverse.

 

Neil

[bizzard]

Here probably lies the problem these days with bigger gearbox selection clunks! where a great many boats these days have enormous output alternators and possibly Travel power units being driven off the poor old engine. More often than not the engines idle speed has to be increased by a couple or so 100 rpm's to cope with the extra load whilst they're pumping out high outputs. When not the engines are left idling at perhaps 900-1000rpm or even more, I've seen and heard em, which won't help with gearboxes clunking into gear nor will the drive plate be too happy about it. All good for business though. Plus boats still zooming along on engine idle-tick over.

[Chalky]

I would be very interested if they recommended something other than what the latest manual says

 

Let us know what you find out

 

Richard

 

Spoke to my father in law. He believes that Newage went bust a few years ago and were bought out and the business continued.

This got me thinking. I know when this happens in some businesses the new management will use this as an opportunity to update / rationalise / cost reduce / delete a product. Is the PRM120 gearbox from 10 years ago the same as the PRM120 now? I don't mean in terms of size and spec etc but absolutely identical in terms materials and internals etc. Could it be that a 10 year old box uses different materials compared to the new one? I know that in the car industry we will change the internals and require different lubricants, fluids, controllers etc but the externals and spec don't change. If this has happened than that may explain the difference.

Edited August 31, 2014 by Chalky

[RLWP]

No idea. Newage split in two IIRC and both parts still trade

 

I suspect that they changed the oil spec based on boat owner experience. Perhaps it caused an unacceptable clunk on engagement or something...

 

Richard

[Chalky]

Just to add to the confusion the PRM website states:-

 

"The normal Operating temperature should be in the range 50° to 120° using good quality lubricating oil of the same viscosity as that used in the engine. ATF Automatic Transmission Fluid is recommended."

http://www.prm-newage.com/p11-prm120

 

Which seems to suggest that both engine oil and ATF are acceptable!

 

Just looked at the manual on the website and its different to the one that I was supplied with. The one on the website is for the PRM120 only, the one I was given by HMI marine covers the all of the PRM mechanical and hydraulic gearboxes.

Edited August 31, 2014 by Chalky

[RLWP]

Right. Only the 80 and 120 use ATF. Newage are very liberal on what oil to use, only two boxes are apparently critical on lubricant - the 80 and 120

 

They are the two boxes that use a sintered conical clutch lining on a bronze hub, sliding on a spiral shaft. Those linings do come apart, meaning loss of gear. That hub has to slide freely to lock the gearbox in gear, or the clutch will slip

 

I would be happy to use engine oil in any PRM box, except for the 80 and 120

 

Richard

[Chalky]

It's due a change so I'll change to ATF. How critical is it to get all of the old oil out? The drain plug on the bottom is difficult to get at and I usually change it using a pump through the fill hole.