Replacing the Slip Coupling on a Volvo MD40A

[nhschneider]

As my wife and I were pulling up to the fuel dock at San Jose del Cabo (southern end of Baja California), I asked her to give it more reverse as she was brining us in a little faster than I prefer. She said, "I'm giving it 2,000 RPMs!", but we weren't slowing down. We were able to dock just fine and when I went below to see what the problem was, I found the prop shaft separated from the reversing gear by about 2 feet.

As it turns out, our Volvo MD40A, which is married to a Volvo MS3 reversing gear, has a type of flex coupling. The prop shaft fits into a collar that's embedded in a very hard rubber-like compound. Since everything on the boat is old, this decided it had worked long enough and gave up the ghost. At least it chose a fairly reasonable location and time. Just days earlier we had been in some very remote anchorages and it could have really stranded us.

As it turns out, Volvo discontinued that part and offers a replacement that doesn't offer the flexibility that our old one did. This worries me. I've own the boat for 13 years and never have aligned the engine to the prop shaft. In fact, I don't think it's possible. The motor mounts are so old and rusted (I know, and in need of replacement) that I'm afraid we'll break something if we try to align it now.

I'm wondering if anyone out there has had any experience replacing one of the Volvo slip couplings. I sure would be interested hearing any details. Thanks.

S/V Rutea
Marina Puerto Los Cabos
San Jose del Cabo, BCS, Mexico