Gotta pay if you’re gonna play

Just over a week into our summer cruise from St. Joseph to points north (we were hoping to make Mackinaw City) the transmission packed it in during our departure from Leland. With a dinghy in tow and a forecast for increasing winds and waves, I was motorsailing in the early-morning light winds when my wife and I heard a noise from below the cockpit that sounded a bit like cavitation. As the boat speed suddenly dropped off significantly, I began going through a mental checklist of possibilities. After confirming that the shaft and propeller were still where they should be, that the prop wasn’t fouled, and that the shift cable and lever were moving/engaging, I concluded that we’d “lost” the transmission.


Transmission packed it in just after leaving Leland. Fortunately, it didn’t quit a couple days before as we were entering in moderate seas, or the day of our departure. All in all, a good time for a transmission failure.

Although it clouded up as the day wore on, we had a beautiful sail up and over the Leelanau Peninsula and dropped anchor in Northport, a familiar harbor where we’ve spent some time on the hook. I immediately began making calls to figure out which was the better option: replace or rebuild. With a new transmission running about $1700 and a rebuild close to the same, the decision was obvious.


We enjoyed a beautiful sunrise and a pleasant sail north.


Preparing to round Cathead Point.

After a little sleuthing online, I came across the TMC60, a better, more reliable gear that should fit. I had several conversations with a very helpful and knowledgeable gentleman from BetaMarine USA and decided to order the trans, which I received two days later. In the meantime, I pulled the old Hurth HBW 10 2 R and made way for the new trans. Unfortunately, these things never go as smoothly as they should; one of the five cap head screws that secure the damper plate to the flywheel stripped. Rather than make things worse while working upside-down and on my head, I reinstalled the other fasteners and planned to continue running the original damper, which appears to be in decent shape.

Incidentally, the fact that it was even possible to pull the old transmission without heroics was due to our stuffing box arrangement. Ariel’s stuffing box screws onto her stern tube, as opposed to other CD’s with a stuffing box that is connected to the stern tube via a short length of hose. Thanks to our shorter, simpler stuffing box, I was able to unbolt the coupler and slide the prop shaft aft until the coupling met the stuffing box. It did take a little maneuvering to get the transmission and adapter plate out, but it wasn’t difficult.


Removing the transmission required unbolting the coupling from the DriveSaver, sliding the shaft aft to the stuffing box, and removing the water lift muffler and bracket.


Cramped quarters, but thank goodness I fit!


Stubborn cap screw in the damper plate. (And a leaky, oily Perkins).


The culprit. Hurth HBW 10 2 R. Pretty decent service for being 37 years old.

Sunday, July 3, with the new transmission – and after driving 5 hours back to Northport – I spent hours jockeying the heavy Perkins 4.108 around, trying to get enough room for the new trans. Cape Dory shoehorned the engine and trans so far aft that there was no way I could get the new trans shift lever – which exits the case on the port side of the box – to clear the hull without raising the rear of the engine 5/8″ and sliding the whole engine forward over an inch. It was clear that I would have to re-engineer the engine foundations in order to accommodate the required position. Summer is just too short for that so, admitting defeat, I pulled the gear out and moved the engine back to its original location (not an easy task, especially in such a confined space).

Back home in St. Joseph, I reluctantly returned the TMC60 and ordered a ZF 12M, which has the same dimensions as the old Hurth and should be a direct fit. Why didn’t I just go with the Hurth in the first place? Two reasons: First, the TMC is a better (less expensive) gear and I was confident it would fit; Second, ZF transmissions have a less-than-stellar reliability record. If you’re interested in researching issues with the ZF, simply Google “Hurth/ZF transmission thrust washer” or “Hurth/ZF transmission slipping” or “Hurth Transmission Problem.” Perhaps the post of most interest is this one on the Cape Dory Board: Hurth Failure

At any rate, the new ZF will be here Friday, and I’ll head back to Northport to install it and get Ariel back to cruising.

Eventually I’ll open the case on the old Hurth and look into the possibility of rebuilding it to keep as a spare. I did drain the ATF and it has a metallic sheen/glitter to it. Word is it’s probably a failed thrust washer, but perhaps more is going on. I can spin the input shaft with one hand and prevent the output flange from spinning with the other, so clearly something is slipping.

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