Piper Boat Owners' Club

A club open to anyone who owns a Piper-built boat

Gnashing Gearbox?

If I knew then what I know now, I would have saved myself a lot of time, hassle and money. I had been a bit disappointed by the harsh ‘gnashing’ noise coming from the gearbox and had registered that fact through Piper Boats to Beta Marine from the beginning (in August 2007). The noise was worst at normal canal cruising speed but maybe having a Hospital silencer on the engine was allowing me to hear the gearbox more? We agreed to wait and see if the noise would settle down as the gearbox bedded in. As the noise only happened in forward gear I triple checked that the direction of rotation, etc., was correct: it was.

Time went by and in 2008 we made the 600 mile circuit from Heritage Marina to Gloucester, Bristol, London and back to Heritage. The mashing noise continued unabated but I suppose we became used to it. The following year, while boating in Holland, we began to hear (and feel) a peculiar thumping noise coming from under the boards just after engaging forward gear before the engine was fully warmed up. At this time the engine had run about 680 hours.

Investigation revealed that the engine was leaping about, but could be calmed down by adjusting the throttle up or down for a few minutes and the problem settled down once everything was up to temperature. On checking we found that one of the engine mounts was loose (hidden under the engine frame) and there was great jubilation, but that turned out to be a red herring (or should that be a ‘rood haaring’?) and the symptoms continued from time to time.

The problem did not always happen and was short lived each time. However, in the spring of 2010, on a trip to Bugsworth with our Dutch friends, the morning juddering became rapidly worse and was occurring again after the lunch stop. Engine hours were now up to 860 and many theories were expounded by all and sundry - could it be the stern tube bearing, the coupling, the drive plate or the engine mounts? - but we really needed expert advice. After a little persuasion Simon sent his man down for a diagnosis and he soon identified clutch slip in the gearbox. He explained that Forewards and Reverse are selected by one of two clutches and that one of these was wearing out - the ‘F’ word!

The engine and gearbox assembly were still under the three year warranty period and Beta agreed to replace the gearbox and in the end supplied the one which we had seen on the stand at Crick!
Now, talking to various fleet engineers, it became apparent that our gearbox as supplied is a PRM 120 ‘mechanical’ type and would not be suitable for hire fleet or extended use. They would only use the PRM150 ‘Hydraulic’ version so I elected to change to the latter and pay the difference. However it turned out more expensive than expected because the hydraulic version also requires an oil cooler, associated pipes and a new drive plate, all plus VAT.

So we set off from Heritage for our summer 2010 trip with our new gearbox working fine and whizzed down the Severn from Stourport to Gloucester and on to Sharpness with a noticeably quieter gearbox - in fact we could now hear water sloshing around the weed hatch! Returning north I checked the gearbox oil (not for the first time!) at Stratford and it looked like runny custard: the new oil cooler had failed internally, mixing cooling water with the oil.

Within a couple of hours Beta had sent a man to replace it and change the oil and we were away again: excellent service. Our next destination was Trent lock at the junction of the rivers Trent and Soar to join the Piper Summer Cruise, but just as we were descending Camp Hill locks we learned that vandals had breached the Birmingham & Fazeley canal which would be closed for (at least) a week, so we had to divert via Farmer’s Bridge, Wolverhampton and Great Haywood. As we passed through Burton-on-Trent a loud knocking began to occur between cruising speed and tick-over speed which turned out to be a failing engine mount and could be temporarily fixed by wrapping some thin rope around the mount.

Yet another call to Beta got the mounts changed under warranty again. It seems that the original severe juddering of the engine assembly had given the mounts a hard time although I hesitate to call it a ‘(k)nock-on’ effect.

Having subsequently cruised down the Trent and on to Boston and back it all seems to be working satisfactorily but it was worrying to hear of similar symptoms from some fellow Piper owners. As I said at the beginning, if I had known what I know now about the different types of gearbox, I would certainly not have specified the cheaper version, but that is hindsight

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