Minimum distance between cutlass bearning and shaft zinc - SailNet Community

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Old 04-06-2009
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Minimum distance between cutlass bearning and shaft zinc

Hi All,

When we installed our engine (Beta 28) the guy who sold us a prop said that we need a minimum of 1/4" clearance between the cutlass bearing and the shaft zinc - which is flush up against the forward edge of the propeller.

I recently discussed with another boat owner and he figures this is much too small, as the engine might ride forward slightly on its mounts when underway, causing the zinc to rub up against the cutlass bearing, restricting water flow and causing all sorts of problems.

In the "acceptable clearances" section of this link it recommends at least 1/2 inch for a smaller engine than ours.

Parts

Any experts out there who can set me straight here? I haven't been able to find much online at all. My prop sits in an extrusion with no strut at all. Total shaft length is very short, approximately 24 inches.

Thanks.
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Old 04-06-2009
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FWIW I have never head of installing a Zink between the shaft strut and the prop. Normally one finds the zinc forward of the shaft strut/cutlass bearing but usually within and inch or so becuase of the extent to which zinc's tend to waste in an irregular manner causing out-of-balance issues with the prop-shaft. Your arrangement seems quite unusual. Any one else have any observations on this? Grodon May?

s/v HyLyte
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Old 04-06-2009
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Do you have room to increase the distance to a half inch then? Also, or there water holes forward of the cutlass bearing for some water flow?

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Last edited by erps; 04-06-2009 at 09:35 PM.
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Old 04-07-2009
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This isn't the greatest angle, but you get the idea. We do have room to move our shaft back slightly, I'm just wondering if its necessary?

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Old 04-07-2009
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Whoa--Sorry old chap. After looking at your set-up, my earlier comment doesn't apply to your situation. I'd try looking into what PS did with the original arrangements when the yachts were built. Good luck...

s/v HyLyte
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Old 04-07-2009
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That looks way too close to my unprofessional eye. You could move it back an inch by installing one of these: clicky click

Good for ya, too!
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Old 04-07-2009
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You can cut those limited-clearance collar zincs down with a band saw. Or you can use a 25mm limited-clearance collar, which are much thinner than stardard-sized limited-clearance zincs (not really the proper fit, but will work).





Beneteau Collar Zinc Anodes
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Old 04-09-2009
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If you look closely at erps cutless bearing, there is an irrigation 'port' drilled forward of the encased bearing. A cruising boat I maintain had the same config. as dhornesy. The bearing lasted about 3 years. When it was replaced the irrigation ports were drilled since the shaft was out. Since the bearings often must be cut out of the shaft log, I specified a phenolic jacketed bearing to ease the effort of cutting it away. The shaft and prop were then sent out for rebalancing.

If you have a ceramic stuffing box and it is irrigated by the engine cooling water, the position of the zinc won't really matter.
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