Delayed prop turn - PRM120D

[sailor0500]

So the 80 and the 120 have been replaced by the 90D and 125D. I wonder what the difference is between the old and the new. Have the clutch cones been beefed up ( as this seems to be the main fault which arises with these boxes ) ? Would be interesting to find out if the clutch cones are the same on the new? boxes.

Edited December 22, 2016 by sailor0500

[RLWP]

So the 80 and the 120 have been replaced by the 90D and 125D. I wonder what the difference is between the old and the new. Have the clutch cones been beefed up ( as this seems to be the main fault which arises with these boxes ) ? Would be interesting to find out if the clutch cones are the same on the new? boxes.

 

I have never actually checked the dimensions, however the clutch in the 120 looks identical to the one fitted to the small ZF and Technodrive boxes

 

Richard

[mross]

PRM120.pdf57fe12faf22ed.pdf

 

 

The, newer, 125 is the same length but is slimmer. Here are their workshop manuals, with dimensions. I emailed PRM to see if the 125 is a 'drop-in' replacement. I guess the mountings are narrower.

Edited December 22, 2016 by mross

[RLWP]

PRM120.pdf57fe12faf22ed.pdf

 

 

The, newer, 125 is the same length but is slimmer. Here are their workshop manuals, with dimensions. I emailed PRM to see if the 125 is a 'drop-in' replacement. I guess the mountings are narrower.

 

I would expect it to be the same ISO bolt pattern as the 80/120/150/ZF/Technodrive etc.

 

Richard

 

MORE: Yep, page 9, Fig 4. That six bolt arrangement with a spigot around the input shaft is common to most small boxes. I addition, they can supply adapters for SAE and Velvet Drive installations

Edited December 22, 2016 by RLWP

[lampini]

Have you tried both ends of the cable?

Confused of the Ashby here again! How would disconnecting the upper end at morse control help??

RLWP posted a brilliant explanation of how PRM mechanical boxes work, in another thread. http://www.canalworld.net/forums/index.php?showtopic=56107&p=1063665

Bluddy Awesome!

 

I only understand half of it; but the fact that I understand half of it is testament indeed to your powers of explanation, Richard! :-0

[mross]

If you can't disconnect it at the gearbox end but can disconnect at the Morse lever this should allow you to operate the lever on the gearbox and see if it moves forward a little more. You probably need an adjustable spanner, end-on, to give you a little leverage. Test with engine running at idle and make sure you have no loose clothing that could wrap around any moving parts. If the shaft now moves immediately, you have found the problem and can make adjustments at the Morse (speed and direction) lever to give more travel at the other end where the cable connects to the gearbox. This lever should move until it comes up against the stops inside.

 

Bizzard's suggestion to wash out the 'box with a mix of paraffin and ATF is excellent as your problem may be gunk on the cone clutches or their spiral drive.

[mross]

 

I would expect it to be the same ISO bolt pattern as the 80/120/150/ZF/Technodrive etc.

Yes, I was thinking of the 'pads' just aft of the lever but I don't know their purpose. I mistakenly thought they were mounts but then realised gearbox is hung off the engine. I have a different 'box on my boat.

 

Richard, what do you charge for rebuilding a PRM 120 with slipping ahead clutch or would that be something you quoted after dismantling?

[mross]

PRM have just replied to my email.

 

"Yes Martin external dimensions are identical"


Best Regards

Andy Clarke
Sales Manager
PRM Newage Ltd
Barlow Road
Coventry
CV2 2LD

Tel +44 (0) 24 76617141 - Ext 220
Fax +44 (0) 24 76611845

Mail a.clarke@prm-newage.com
Web www.prm-newage.com

[RLWP]

Richard, what do you charge for rebuilding a PRM 120 with slipping ahead clutch or would that be something you quoted after dismantling?

 

It's safer to quote once you know what is wrong

 

Richard

 

MORE: Cones are still available: http://www.asap-supplies.com/engine-spares-gearboxes/marine-gearboxes-and-spares/marine-gearbox-spares/prm-mt8098-clutch-cone

Edited December 22, 2016 by RLWP

[mross]

So the 80 and the 120 have been replaced by the 90D and 125D. I wonder what the difference is between the old and the new. Have the clutch cones been beefed up ( as this seems to be the main fault which arises with these boxes ) ? Would be interesting to find out if the clutch cones are the same on the new? boxes.

The part number for the 125 cone clutch is 'MT8098 MT8661'

 

The part number for the 120 cone clutch is 'MT8098'

[RLWP]

The part number for the 125 cone clutch is 'MT8098 MT8661'

 

The part number for the 120 cone clutch is 'MT8098'

 

Which suggests the 125 uses a cone with the same dimensions as the 120

 

Richard

[AndrewIC]

Yes, I was thinking of the 'pads' just aft of the lever but I don't know their purpose.

They are for the bracket to which the outer part of the operating cable is fixed.