lampini Posted December 11, 2016 Report Share Posted December 11, 2016 Wot it says in the title... Start engine, into gear and nothing - for about 5 seconds and then the prop starts churning properly. It happened when we set off from the mooring on our last cruise but then all was good for the rest of the cruise. Gearbox PRM120D transmission fluid about 1-2cm above mark on dipstick.. difficult to tell as is clear fluid! Got OH to observe driveshaft and it is THIS which starts to turn really slowly at first and then suddenly speeds up, so i may be wrong but don't suspect the prop.. v difficult to access weedhatch! Help? (Beta 38 engine btw....) Link to comment Share on other sites More sharing options...
Tony Brooks Posted December 11, 2016 Report Share Posted December 11, 2016 As long as the control lever on the box has its full travel I fear slipping and thus worn out ahead clutch. Take the control cable off the gearbox lever and operate the lever by hand to see if it cures it. If it does then you need to lok at cable adjustment and possibly repositioning the cable on the lever in the control. 2 Link to comment Share on other sites More sharing options...
Chewbacka Posted December 11, 2016 Report Share Posted December 11, 2016 As long as the control lever on the box has its full travel I fear slipping and thus worn out ahead clutch. Take the control cable off the gearbox lever and operate the lever by hand to see if it cures it. If it does then you need to lok at cable adjustment and possibly repositioning the cable on the lever in the control. But if it doesn't then sadly it's time to get the gear box serviced.......... Link to comment Share on other sites More sharing options...
lampini Posted December 11, 2016 Author Report Share Posted December 11, 2016 As long as the control lever on the box has its full travel I fear slipping and thus worn out ahead clutch. Take the control cable off the gearbox lever and operate the lever by hand to see if it cures it. If it does then you need to lok at cable adjustment and possibly repositioning the cable on the lever in the control. Thanks Tony (again!) - will try the test and report back - probs tomorrow now as am at my mum's trying to make the fairy lights work... a bit more of a simple job - for me - lol! Link to comment Share on other sites More sharing options...
Ryeland Posted December 11, 2016 Report Share Posted December 11, 2016 I had exactly the same symptoms. Forward clutch shot. Suggest you contact Primrose Engineering (RWLP of this parish) for a rebuild. Richard 2 Link to comment Share on other sites More sharing options...
AndrewIC Posted December 11, 2016 Report Share Posted December 11, 2016 Gearbox PRM120D transmission fluid about 1-2cm above mark on dipstick.. difficult to tell as is clear fluid! According to the manual the dipstick mark is a maximum, so you may be overfilled. Unfortunately I can't remember whether the level is supposed to be read with the dipstick screwed all the way in or not! You can see the level by placing the stick onto a piece of white tissue/kitchen paper/loo roll, then the red ATF shows up much more clearly. Link to comment Share on other sites More sharing options...
lampini Posted December 11, 2016 Author Report Share Posted December 11, 2016 According to the manual the dipstick mark is a maximum, so you may be overfilled. Unfortunately I can't remember whether the level is supposed to be read with the dipstick screwed all the way in or not! You can see the level by placing the stick onto a piece of white tissue/kitchen paper/loo roll, then the red ATF shows up much more clearly. Level IS read when screwed right down - sezzit in the manual! Will do the kitchen roll thingy tho - Excellent wheeze there Andrew.... I won with the fairy lights btw... Has probs given me an over-inflated sense of my own mechanical abilities now! God help that poor gearbox... Interested to see if it is red fluid - it really seemed just this clear thin stuff..... Hmmmmmm... Link to comment Share on other sites More sharing options...
Tony Brooks Posted December 11, 2016 Report Share Posted December 11, 2016 I understand the change to red ATF was because of "clutch troubles" but have no further info. Link to comment Share on other sites More sharing options...
AndrewIC Posted December 12, 2016 Report Share Posted December 12, 2016 Level IS read when screwed right down - sezzit in the manual!. Thanks, I couldn't find it in my scanned copy, all I could remember was that it's the opposite way round from a Hurth box! Link to comment Share on other sites More sharing options...
Tony Brooks Posted December 12, 2016 Report Share Posted December 12, 2016 However if you just place the dipstick in the hole without screwing it in the minimum mark then becomes the maximum and the end of the dipstick the minimum. Link to comment Share on other sites More sharing options...
mross Posted December 12, 2016 Report Share Posted December 12, 2016 (edited) I realise now that the 120 is mechanical, not hydraulic One way to get the best life out of hydraulic gearboxes is to never go straight from ahead to astern or vice versa without letting the revs drop to idle. In emergency you can go from full-ahead to full-astern but it will cause wear on the clutches. This is true for many marine gearboxes. Edited December 12, 2016 by mross Link to comment Share on other sites More sharing options...
lampini Posted December 12, 2016 Author Report Share Posted December 12, 2016 However if you just place the dipstick in the hole without screwing it in the minimum mark then becomes the maximum and the end of the dipstick the minimum. Oo - er! Think I geddit... Even tho we liveaboard I have pulled 4 days of 10 plus hour shifts so I'm not gonna be able to sensibly have a look-see with the cable until Friday realistically... This is with my sensible head on - realising that sticking my head in the engine bay after a day like I've had wouldn't be sensible at all ... Grrrrr... Wanna play with my engine!!! Link to comment Share on other sites More sharing options...
lampini Posted December 12, 2016 Author Report Share Posted December 12, 2016 I realise now that the 120 is mechanical, not hydraulic One way to get the best life out of hydraulic gearboxes is to never go straight from ahead to astern or vice versa without letting the revs drop to idle. In emergency you can go from full-ahead to full-astern but it will cause wear on the clutches. This is true for many marine gearboxes. Is this still relevant, and therefore good. Practice for mechanical gearboxes then? Please feel free to plant any gearbox gems you may have here - I won't be doing much apart from work and read this in my breaks until friday ... Mind you - gearbox on my bus sounded like it was grinding washers today.. "Oh it'll be fine - just a bit noisy!" No Sh%t Sherlock! All gearbox jokes gratefully received too... :-) Link to comment Share on other sites More sharing options...
mross Posted December 13, 2016 Report Share Posted December 13, 2016 Well, your gearbox contains cone clutches and I imagine you will get a better life out of them if you change gear at idle . Here's a link to the workshop manual 1 Link to comment Share on other sites More sharing options...
lampini Posted December 13, 2016 Author Report Share Posted December 13, 2016 Well, your gearbox contains cone clutches and I imagine you will get a better life out of them if you change gear at idle . Here's a link to the workshop manual Cheers - funny how it says to use engine oil not ATF innit?! ?? There's ATF in there and that's wot they say in the Q&A on their website; and a couple of other places wot i cannae remember right now - but mucho confusiferlous eh? Link to comment Share on other sites More sharing options...
lampini Posted December 14, 2016 Author Report Share Posted December 14, 2016 A final question before I manage some daylight and another pair of eyes to check wots going on at the weekend...... Assuming the worst and it IS the clutch... Given that this delay in prop rotation only happens in the very first burst of forward gear, and that it seems to perform as normal thereafter - how fast can I expect this situation to degenerate until I have no prop turn at all? Or is that impossible to say? Cheers!! Link to comment Share on other sites More sharing options...
mross Posted December 14, 2016 Report Share Posted December 14, 2016 (edited) PRM hydraulic gearboxes use engine oil but mechanical ones use ATF. The link I sent you for the workshop manual specifically says ATF if you read it! If the ahead clutch is on the way out it will suddenly start to slip and you might get stranded. So I recommend that you do something before planning any long trip! http://www.ebay.co.uk/itm/PRM-80-PRM-120-Gearboxes-/162305350028?hash=item25ca27198c:g:LVYAAOSwx-9WwO1u http://www.ebay.co.uk/itm/Pmr-120-Marine-Boat-Gearbox/282291004582?_trksid=p2047675.c100009.m1982&_trkparms=aid%3D888007%26algo%3DDISC.MBE%26ao%3D1%26asc%3D38661%26meid%3D3a14f342b4c04bbfbadba4fe2b27b686%26pid%3D100009%26rk%3D1%26rkt%3D1%26sd%3D162305350028 But you need to check if the latter has the correct ratio. Prm120 is obsolete, replaced by the 125. Edited December 14, 2016 by mross Link to comment Share on other sites More sharing options...
ditchcrawler Posted December 14, 2016 Report Share Posted December 14, 2016 PRM hydraulic gearboxes use engine oil but mechanical ones use ATF. The link I sent you for the workshop manual specifically says ATF if you read it! If the ahead clutch is on the way out it will suddenly start to slip and you might get stranded. So I recommend that you do something before planning any long trip! http://www.ebay.co.uk/itm/PRM-80-PRM-120-Gearboxes-/162305350028?hash=item25ca27198c:g:LVYAAOSwx-9WwO1u http://www.ebay.co.uk/itm/Pmr-120-Marine-Boat-Gearbox/282291004582?_trksid=p2047675.c100009.m1982&_trkparms=aid%3D888007%26algo%3DDISC.MBE%26ao%3D1%26asc%3D38661%26meid%3D3a14f342b4c04bbfbadba4fe2b27b686%26pid%3D100009%26rk%3D1%26rkt%3D1%26sd%3D162305350028 But you need to check if the latter has the correct ratio. Prm120 is obsolete, replaced by the 125. Mine died on the Chesterfield Canal, thankfully not on the Trent getting there. Link to comment Share on other sites More sharing options...
mross Posted December 14, 2016 Report Share Posted December 14, 2016 If ahead clutch fails you can get home by going astern! Link to comment Share on other sites More sharing options...
ditchcrawler Posted December 14, 2016 Report Share Posted December 14, 2016 If ahead clutch fails you can get home by going astern! Up the Trent against the flow ? Link to comment Share on other sites More sharing options...
mross Posted December 14, 2016 Report Share Posted December 14, 2016 (edited) Well, better than going downstream with no steerage! Even if you can't makes any headway you can get to the bank and throw a mud anchor! Edited December 14, 2016 by mross Link to comment Share on other sites More sharing options...
sailor0500 Posted December 15, 2016 Report Share Posted December 15, 2016 Wot it says in the title... Start engine, into gear and nothing - for about 5 seconds and then the prop starts churning properly. It happened when we set off from the mooring on our last cruise but then all was good for the rest of the cruise. Gearbox PRM120D transmission fluid about 1-2cm above mark on dipstick.. difficult to tell as is clear fluid! Got OH to observe driveshaft and it is THIS which starts to turn really slowly at first and then suddenly speeds up, so i may be wrong but don't suspect the prop.. v difficult to access weedhatch! Help? (Beta 38 engine btw....) I had same problem. Almost as cheap to buy new box if you shop around for best price as the clutch cone is expensive plus labor of stripping. Try ASAP Supplies. Link to comment Share on other sites More sharing options...
mross Posted December 15, 2016 Report Share Posted December 15, 2016 I had same problem. Almost as cheap to buy new box if you shop around for best price as the clutch cone is expensive plus labor of stripping. Try ASAP Supplies. RCR will recondition for £350 as per my earlier eBay link. Link to comment Share on other sites More sharing options...
sailor0500 Posted December 15, 2016 Report Share Posted December 15, 2016 RCR will recondition for £350 as per my earlier eBay link. As opposed to £600 for a brand new box. You pays your money............. Link to comment Share on other sites More sharing options...
ditchcrawler Posted December 15, 2016 Report Share Posted December 15, 2016 I bought a reconditioned one when mine failed, it was a mistake as it came with a 6 months guarantee and only lasted a year. Link to comment Share on other sites More sharing options...
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