R&D Flex Coupling and Split Flange

I have a new 1.25" shaft, a new R&D shaft coupling and new R&D flex coupling and have a few questions about installation. If you have done it before how did you measure the distance at the red bolt head as the limited directions say. The directions say to use feeler gauges but the distanced is such that it would be a stack of many gauges, is this acceptable? Also I do plan on having the flange fitted to the shaft by a shop. The fit of the flange on the shaft now is an easy slide on fit. It is a split coupling so I guess this is all right?

ak-guy said:

I have a new 1.25" shaft, a new R&D shaft coupling and new R&D flex coupling and have a few questions about installation. If you have done it before how did you measure the distance at the red bolt head as the limited directions say. The directions say to use feeler gauges but the distanced is such that it would be a stack of many gauges, is this acceptable? Also I do plan on having the flange fitted to the shaft by a shop. The fit of the flange on the shaft now is an easy slide on fit. It is a split coupling so I guess this is all right?

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I installed one on my last boat and don't quite understand your concern. The red bolt head is pretty close to the flange face. Here is a pic I found of a typical installation.

Combining or stacking the feeler gauge blades works just fine as you are only looking for the relative difference in gap measured at 90° intervals, not the exact gap. Just vary one blade as required, and leave the other blade(s) in the 'stack' unchanged.

As for the flange fit on the shaft, it should have NO play, but a smooth sliding fit is OK.

I've got a similar shaft coupling & flex coupling but not R&D, which I've had on and off a few times.

I had a look at the R&D installation procedure at R and D MARINE : Flexible Shaft Couplings

Yes - the gap will be more than one feeler gauge in thickness, so you'll have to stack them. They are still relatively accurate as long as the feeler gauges aren't old & corroded. Alternatively you can use a hard piece of steel, plastic, or anything of uniform thickness, plus one or two feeler gauges because you are only comparing the difference in measurement at each 90 degree interval. The total measurement is not important.

In regard to the split coupling, they should be a relatively easy slide on by hand, but you shouldn't have any noticeable movement other than lengthwise on the shaft.

edit - looks like Larry has got it covered

AusCan said:

edit - looks like Larry has got it covered

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You know what they say about 'Great Minds' . . . . . .

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.