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Old 03-29-2017, 10:35 PM   #5
Nomad Willy
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City: Concrete Washington State
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 18,743
I like those flexable couplings.
And I consider the alignment feature a plus.
However there's a great danger in their use.
As the thrust becomes greater the plastic plates bend. Choosing the right sized coupling is very important because if you get one too small there will be enough thrust to move the bolt heads close enough so they hit the opposite shaft flange. This will be similar to taking a jackhammer to the output shaft of the gear and it's thrust bearing. You know when that happens because there will be marks on the bolt heads and the shaft flanges. If this continues over a period of time you'll need to fix your trans thrust bearing at least. It happened to me. My very soft and flexable Yanmar engine mounts may have played a part in my transmission damage. Don't think so though as the max movement is at idle and max thrust is at high power.

But if the coupling is correctly sized there probably will be no trouble. I think they are sized to power rating. Hp ratings vary even w the same engine but thrust varies even more so with lower gears. So if the couplings are for a 120 to 160hp engine and you have a 140hp engine you better get the 160 to 200hp coupling. All these numbers are just as an example.
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Eric

North Western Washington State USA
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