adagio

I needed to speak to PRM today to find out the size of the locking nut on the output shaft, I have every socket up to 28mm. Sods law I needed a 30mm! Whilst talking to the guy I said what is the best way to hold the shaft to undo the locking nut? He asked if the gearbox was still on the engine, which I confirmed it was, to which he said no problem. Start the engine, engage forward drive to get the prop to turn, and then turn off the engine. I did this and then just undid the locking nut no problem at all!

It could well have. Once I’ve got the accumulator fitted I will open up the old pump and see what the situation is inside out of curiosity. I’ll let you know what I find but it will be a while as we’re leaving the boat for a while.

I exchanged like for like models, and Jabsco confirm they’re identical but made no mention of any accumulator. It was only when I explained the issues they felt fitting an accumulator would help solve the issue providing it was of sufficient size, I.e., not a 1 or 2 litre model. Talking them through our usage and outlets they suggested an 8l. The failed pump, which was fitted prior to our ownership, was fitted without a filter and the new pump came with a filter in the box so I fitted it. The filter also affects the pump.

Hi Guys, thank you very much for your thoughts on the matter, especially you Tony who is an amazing font of knowledge. Since seeking your council I have had a long conversation with Jabsco who by and large agree with you Tony on the subject of accumulators, why am I not surprised. So I'm gong to install an 8l accumulator which Jabsco suggest will help. We'll see. Thanks again for your help.

My Jabsco water pump started leaking so rather than use a service kit, the pump is 7-9 years old, I thought I would replace it for a new one, like for like, and keep the other for a spare. No problem fitting the replacement pump but it seems it is pumping at a higher pressure and using the shower, for instance, the pump is pulsing quite dramatically to start with and the same happens when using the washing machine. If we open say the sink tap full on no problem. In addition to the shower, sink, and washing machine, we have the bathroom sink and cassette flush. Would I be right in thinking we need an accumulator to solve the problem?

I have a brass rod with marks corresponding to the top of the gearbox and oil levels. Saves all the fiddling about screwing & unscrewing.

Thank you for your helpful suggestion which I will investigate.

Simple engineering at its best, thank you I very much appreciate the time you have taken to answer my question. I feel scraped knuckles coming up!

Thank you for your reply, appreciated. Prior to the change of oil at the last service I've always had slight signs on oil around the breather after a days run (4-5hrs). Spoke to PRM and they suggested I changed the breather for a new one which I did but the problem didn't go away.I spoke to PRM and all they could offer was keep the oil level low in the box at about the bottom mark, (I usually fill to the mid point between marks). Since the service this has stopped to be replaced by a slight leak on the output shaft, hence my remark about pressure. I am happy to replace the seals but what is the best way hold the flange to undo the nut?

I have a small leak on the output shaft of my PRM120 gearbox when the gearbox is working suggesting it is caused by an increase in the oil pressure whilst working. Replacment seals are easily available so my question is can I replace them myself, what are the pitfalls, if any, and if so do I require specialist tools? I service my own engine and have experience in both petrol & diesel engines etc., so quite confident if pointed in the right direction. Thank you.

No we didn't measure anything. When I went into our chandlers with the old coupling they said yes that was a R&D inch and a quarter coupling. At that stage it never occurred to me, or them, to question what shaft I had. So beware in the future if faced with this problem. Since fitting the new coupling I have spoken again to the marina again and they said. 'Oh yes, if you have a Vetus shaft you must have one of their couplings'! Moral of the story tell them what shaft is fitted. A lesson learnt by me and hopefully posting this may save someone else from a drydock to replace a shaft.

I assume the previous owner of the boat manage some cruising with it as the engine had done some 1300hrs. However the more the shaft was scored the harder it was to clamp it tight. My failing, certainly inexperience, was not knowing the difference between Vetus & R&D standards. Imperial v metric in 2016.

My PRM120 gearbox has started blowing oil out of the breather hole when we are cruising. As far as I can see the more power from the engine the more oil is blown out. We are talking a few millilitres each time. The oil level in the box is where it should be and not overfilled. With engine stopped and the gearbox cleaned of all oil there are no leaks. Running the boat at slow speed and with a cloth around the breather (very temporary) there are no other visible leaks. Suggestions pleased.

To all those who provided advice, suggestions, solutions, here is an update. I replaced the coupling as suggested using the loctite and replacing with new nuts and bolts on both the flange and coupling. A day after the work was done we took the boat for a test run and the coupling failed almost immediately. A passing RCR guy suggested moving the shaft towards the stern to see if we could get a better fix on part of the unscored part of the shaft. That worked for a day then that failed above the River Trent below Fradley junction. RCR suggested a tow to a marina but Steve from Shobnall Marina came out and as a temporary measure inserted some makeshift shims to get a fixture. This got us going to Shobnall with a date for dry docking and a permanent fix. Steve phoned on our way to the dock and said he had indentified the problem, which I and many more experienced missed. The Vetus shaft (which I didn't know I had) is 30mm but the coupling I had was a R&D and measured 1 ¼ inches!! A difference in diameter of about 0.03. No wonder it could never be fully tight! A lesson learnt by me.

Thanks, I can't fault your logic. It will be loctite for the summer then a re-build. Thanks again.

Again more positive and helpful suggestions, thank you. I think a 'friction fit' as in this case is possibly the least cost option in boat building terms and one which should be considered carefully, which I'll do if and when I buy my next boat! Thanks for all your help.

Yes, removing the shaft and turning it down is the correct engineering fix and it something I hope to do next winter but I'll use the previous suggested fixes to enjoy the season. Again thank's for another excellent suggestion

Thanks guys for the suggestions & ideas, excellent and very much appreciated. We're back to the marina tomorrow so I'll borrow a torque wrench and get some loctite for the best of both worlds.

Because of ill usage by either the previous owner or an over exuberant marine engineer, recently prop walking the boat, the drive shaft in our 52' narrow boat has worked loose on two previous occasions when others were using the boat. Worryingly it happen again to us whilst we were on the lower reaches of the River Soar approaching the Trent. Fortunately I had sufficient way to reach, just, the bank side and securely moor the boat. The shaft had worked loose from the half coupling thus causing the bolts on both this and the drive plate to the gearbox to loosen. I slacked back all the nuts & bolts and this enabled me to push the shaft fully back into the coupling. In so doing I noticed that the coupling end of the shaft is badly scored. I then tightened the nuts & bolts of the coupling & drive plate as hard as I could,in an orderly fashion, without the use of a torque wrench. (I don't think the Travis Perkins ballast bag which got around the propeller & rudder the previous evening helped and may have even stressed the coupling causing it to work loose!) I have marked the shaft and coupling to enable me to check the alignment and after 3 hours motoring there was probably a slight movement between shaft & coupling of about 2mm but this remained unchanged after a further 3 hours motoring. My question is therefore what further measures can I take to ensure a better/permanent solution so this doesn't recur other than take the boat out of the water and put in a new shaft, et al, this early in the season. Would I be better fitting a new coupling immediately to replace the existing old one? All help would be greatly appreciated