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coling...
coling...

Posted: Sun Aug 17, 2008 6:13pm

Post Subject: engine thrust

Hi Could someone help?.We own a 25 foot all steel narowboat with a Nanni 2.4he inboard diesel engine with a Hurth 50 gear box. The problem is that we generate very little drive. anything above half throttle the engine sounds like it is working very hard but the prop just seems to be thrashing the water about behind the boat but giving very little extra forward movement.We have calculated that we can never get up to anything like 4 mph and any small thing like a couple of leaves in the weed hatch has a big effect on output and makes the tiller vibrate badly. could it be that the wrong size prop is fitted or some other problem. Thanks colin

Tony-B...
Tony-B...

Posted: Mon Aug 18, 2008 10:11am

Post Subject: engine thrust

Dear Colin, As soon as I get this type of question & I see "Hurth" I immediately think "slipping ahead clutch" but the bit about the prop thrashing the water may indicate something different. Are you sure there is nothing around the prop or shaft. Sometimes you really have to feel down deep to find some rope or something that is hanging down off the shaft. Have you also carefully compared the feel of each prop blade to ensure you have three blades and they are all of a very similar shape and size. It could be a bent or damaged prop. I suggest that you go onto the Nanni website and see what size prop they recommend and then compare it with what you have got. the numbers should be stamped on the boss somewhere. Also watch the shaft whilst you increase the engine revs. If it looks as if the engine is increasing in speed but the shaft is not then its a slipping clutch in the gearbox. Tony Brooks

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