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AuthorMessage
deotto
deotto

Posted: Wed Aug 12, 2009 4:07pm

Post Subject: prop shaft

I have recently had a new engine fitted to my 39ft narrowboat. While they were at it, they changed the prop shaft and propellor as it was worn. When I drive the boat now,I find that it is less responsive than before and it doesn't turn as easily. I checked through the weed hatch and I found that the new propellor sits a lot closer to the hull than the old one did. Should I ask them to fit a longer prop shaft, or should I just get used to the new setup?

Tony-B
Tony-B

Posted: Wed Aug 12, 2009 7:08pm

Post Subject: prop shaft

Dear Otto, I suspect the prop-shaft length would only have a marginal effect as long as there is some gap between the prop and outboard bearing. My suspicion is that the new propeller is a different size , possible smaller or with less pitch. That would account for your symptoms but I can not say it is the wrong size, it could be the old one was too large in some way. I have just fitted a new prop and it's size as advised by Crowthers was confirmed by my own and third party calculations. I now find my cruising RPM have gone up from about 1200 to 1500 but the fuel consumption has marginally improved, as has top speed. I tell you this because I just need more revs to get the boat to perform as before and it sounds as if you are in a similar position. Without a lot more info I can not advise on the correct prop size and even then experience is important. Tony Brooks

deotto
deotto

Posted: Thu Aug 13, 2009 11:21am

Post Subject: prop shaft

Thanks Tony, much appreciated.

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