FLEXABLE SHAFT COUPLING FOR YANMAR

Tim Lackey, Glissando, #381

You asked about flex couplings for your Yanmar. I have one of them on my shaft. I get no shaft vibration, and the engine is now totally isloated by rubber from the shaft and foundation. The engine shakes all over the place, as small diesels do, but none of that is tranmitted to the hull or shaft. Pretty slick.

The coupling I have is available through Yanmar. It's different than a drivesaver in that the coupling is two metal plates with firm rubber sandwiched between. (See the photo). When I repowered last summer, this coupling was recommended by my dealer instead of the standard Drivesaver because of its superior flex/isolation characteristics, especially when used as designed in conjunction with the standard Yanmar engine flex mounts. Otherwise, it installs and acts about the same, and will shear in the event of an unwanted impact with some firm object.

Installing the flex coupler requires cutting down the shaft by 1" (the width of the coupling). But it is very effective at vibration isolation and, in my mind, seems almost a necessity given the very rubbery vibration damping mounts that are standard with the Yanmar. And if you suscribe to the electrical islolation theory of metallic installations, you need a non-metallic coupler between the engine and shaft in order to complete the true isolation. If your boat is electrically bonded, then you don't need the flex for this purpose.

Here's a link to one Yanmar dealer online showing the coupling that I have:

(ed. for more information on Tim's total Triton restoration, visit his web site at: http://www.triton381.com/)