An uncharacteristic dripping of seawater into his Beneteau's usually dry bilges heralds an unscheduled haul-out for Stu Davies…
As the launch cradle dropped us in, Bruce called out his usual, “All OK?” before disconnecting us from the slings. We’d splashed our Beneteau 381 after a lift and antifoul at Bruce’s yard in Faro this summer and I’d performed my usual dash below to check for any leaks and to burp the Volvo-type seal.
I noticed the shaft seal didn’t immediately stop dripping when I released it as it usually does, but as it did stop dripping after a few seconds it wasn’t a major concern. I made a mental note to grease it again and to keep an eye on it.
My engine is a Volvo Penta MD22 with an MSE2 gearbox and a shaft drive through a Volvo Penta dripless seal and a rubber cutless bearing – a system is commonly used on Beneteaus and other French boats.
The dripless seal is sold by Volvo Penta but is used on other boats for other engine combinations. There are also ‘pattern’ versions made and sold by other manufacturers.
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Two weeks later, I did a check of the seal, more by accident really, and was horrified to see it dripping. My bilges do dust rather than moisture so this was not a good sign.
I got on the phone to Bruce’s Yard to see if he could lift us and then got on to Sopremar in Portimão to see if they had a new one in stock.
The answer was yes on both counts and Bruce could lift us immediately. Off we set, it was only a couple of miles down to the slings ready for work to commence.
At this point I must confess that I’d used a Volvo rubber shaft seal clone previously. There are a few of them on offer now, quite a bit cheaper and supposed to be just as good.
The Volvo Penta one is about £90, the clone £70, but the Volvo one in Portugal cost me €150, and with the cost of the lift… Ouch!
The Volvo seal is a rubber moulding which consists of what looks like a rubber cutless bearing and two lip seals.
The ‘bearing’ supports the shaft at the inboard end which also has a small water feed to it from a through hull fitting. Some manufacturers use part of the exhaust cooling water discharge to lube them.
To change the seal is quite easy. Four prop shaft flange bolts are removed to separate the flanges at the gearbox. The flange is held to the shaft by a nut and a feather keyed taper.
Dripless shaft seal replacement: Step-by-step
Tighten the puller up and then give the boss of the flange a sharp tap with a hammer to shock the taper into releasing. Make sure you don’t lose the feather key after removing the flange and also mark it to make sure it goes back in the same orientation.
They can have slightly different dimensions and it’s possible for the key to stop the taper on the flange from mating correctly if it’s put back differently.
The seal is held onto a fibreglass tube bonded to the hull, by stainless bolts through a clamp, which are undone and then the seal is slid off the shaft. The new one came with a plastic split protector which was inserted into the new seal with lots of silicone grease on it.
Changing a cutless bearing
While the boat was out of the water I decided to change the exterior cutless bearing as well. This had felt good when I’d inspected it before launching a month previously but there was about 1mm of lift in it now. Luckily I had a spare on board.
The cutless bearings on Beneteaus are simple fluted rubber ones and are not difficult to change, but the prop and rope cutter have to be removed which can sometimes prove difficult.
Once you’ve got these off two plastic 6mm screws locate and hold the bearing in position.
Pedantry corner: cutless not cutlass!
One of the most common mistakes in nautical terminology is referring to cutless bearings as cutlass.
The technology was a serendipitous discovery made in the 1920s by American mining engineer Charles Sherwood who discovered when he ran out of his usual bearings that the abrasive muddy water ‘cut less’ into the shafts of his pumps when he used fluted rubber instead of lignum vitae bearings.
Hence he soon patented it as his ‘cutless’ bearing. The other spelling is of course a pirate sword, confusingly also nautical, but the mix-up is so rife that even several online chandlers have them listed as cutlass bearings!
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This feature appeared in the August 2022 edition of Practical Boat Owner. For more articles like this, including DIY, money-saving advice, great boat projects, expert tips and ways to improve your boat’s performance, take out a magazine subscription to Britain’s best-selling boating magazine.
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