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shundraw
shundraw

Posted: Mon Jun 02, 2008 9:22pm

Post Subject: Propeller shaft whine

I have a 45 foot narrowboat built in 1992, which is suffering from a whine from the propeller shaft at lower revs ,from idle at an indicated 650 revs to about 700 revs when going ahead and from about 850 to 1000 when going astern. I suspect the rev counter is reading about 150 to 200 revs low by the way. The engine is a Beta 1505 with a PRM 120 gearbox (2:1 ahead and 2.5:1 astern I believe) The gearbox was fitted in February 2004 to replace a Borg Warner, new engine mounts were installed at the same time. The gearbox was overhauled in December 2007 when a needle bearing was replaced. The propeller is a 17” x 10” with a 1.5” shaft, both shaft and stern tube were replaced in January 1999. A flexible coupling is installed referred to in the build specification as a Uniflex type, but it looks exactly like the coupling shown in the Centa advert in Canalboat. The stern gland has been re-packed and there is plenty of grease going from the greaser. The whine has becoming louder over the last few months, which was the reason for the gearbox overhaul which, unfortunately has not had any effect on the noise. It has been suggested that a “Crowther” propeller might solve the problem, but I am reluctant to incur further costs unless there is a reasonable chance of success. Apart from this problem the engine runs perfectly. Thanks for your help.

Tony-B
Tony-B

Posted: Tue Jun 03, 2008 9:21am

Post Subject: Propeller shaft whine

Please read the thread I gave in the other singing prop question, but as your problem seems to be all at low speed there are other things to check. Tighten all the fixings on the engine feet, especially those holding the mounts to the beds. Carefully check the shaft is absolutely concentric with the hole in the sterngland. If there is any eccentricity get the engine realigned. I think your coupling ill only deal with angular misalignment, not radial. Remove the weedhatch and inspect it for any signs of the anticavitation plate vibrating against the hatch trunk. If you find any either strengthen the fixings for the plate or grind it to increase the clearance a little. Make up a temporary weedhatch cover from plywood and try the boat with that in place. If the noise goes try raising the anticavitation plate by lifting the whole assembly by using a much thicker gasket material. Once that has been done then de-knicking the prop using an angle grinder might help. I very much doubt that anyone will give you a definite yes to your question about a new prop because what works on one boat does not seem to work on others. I am very surprised that no-one used a screwdriver or length of wood as a stethoscope to try to localise the whine to the gearbox bearing before overhauling it. One other thing, but whine is not the usual way of describing the is that some PRM boxes suffer chatter caused by an inappropriate drive plate, but this usually only occurs in neutral. I mention this just to show the range of possibilities one has to consider. Tony Brooks

shundraw
shundraw

Posted: Wed Jun 11, 2008 4:33pm

Post Subject: Propeller shaft whine

Thanks Tony - I had a feeling it was a bit black art stuff. Mike

THOMAS
THOMAS

Posted: Thu Aug 07, 2008 8:53pm

Post Subject: Propeller shaft whine

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