A damper on my birthday

Continuing to catch the blog up here, going back to our arrival in Fort Lauderdale mid-January. This entire post will concern the replacement of the transmission damper plate, so if you have no interest in such matters, feel free to skip it.


Torsional Coupling (Vulkan Torflex stock photo).

At the end of January I completed another trip around the sun, and on that same day I installed my "birthday present," a shiny new transmission damper plate. It's been a while since I mentioned the damper issue here, so as a refresher, and for anyone who arrived at this post via a link in another forum, a brief recap:

In a bit of foreshadowing, we had dinner with our friends Michel and Caroline of the Nordhavn 50 Sea Turtle when we ran into them in Beaufort, NC on our way south in November. Michel and I had a long chat about maintenance, since the N50 has the exact same drive train as Vector, a Lugger 6108 coupled to a ZF280. One of the things we discussed was the damper plate, how it was generally recommended to replace it at 5,000 hours, and how we were both approaching that milestone.

And thus it was that, just two weeks later, during a passage from Charleston to Jacksonville, we noticed the tell-tale sounds of a damper plate going bad. Louise noticed it first, and by mid-passage it was loud enough that she needed earplugs to sleep. We ran through the night before stopping the boat to investigate the noise, which we quickly confirmed was transmission related.

In Jacksonville I started digging into what it would take to replace it. And the first brick wall I ran into was that we had no documentation telling us what damper plate we had in the boat. It's not in the engine parts manual, nor is it in the transmission service manual. We even called Lugger, who had sold the engine and transmission already coupled together as a completed unit, who confessed that it was not listed in our build sheet. I also contacted some Nordhavn 50 owners to see if anyone knew.

A lot of Internet sleuthing suggested that the ZF280 was normally supplied with a Vulkan Torflex coupling, but we still had no part number. In a stroke of luck, after moving the boat in Jacksonville, the coupling stopped in exactly the spot where I could see, through the ventilation slots, that there was a sticker on it. Close inspection revealed a Torflex part number, and even the date of manufacture and original invoice number. This also confirmed beyond doubt that the damper had never been changed since the power-train was assembled.


Our new damper awaiting installation atop the engine valve cover. Vinyl hose was on standby in case we needed to reroute the shaft sump during the project.

I called the ZF parts distributor for the eastern US, Transmission Marine, who happens to be in Fort Lauderdale, to ask about changing the damper and sourcing the part. They quoted me $850 for a new damper, supplied a ZF part number (3207316014), told me they could do the replacement only if I brought them the whole transmission, and referred me to an itinerant mechanic in Fort Lauderdale who works on ZF in the field. I also called Yacht Tech in Palm Beach, who services a lot of Nordhavns, who told me they contracted that kind of work out and also gave me a referral. And I called a couple of marine transmission outfits in Jacksonville, since that's where we were.

I'd heard quite a few horror stories about damper plates exploding underway, in some cases with parts jamming the flywheel and causing engine damage. So I was very relieved when further research revealed that Torflex couplings are "fail safe." When the rubber isolators disintegrate, they remain contained within the fully enclosed damper unit, and power can still be transferred to the transmission, but at reduced horsepower to minimize undamped load on the transmission and engine.

That gave us more options than replacing it right there in Jacksonville, even though we booked a month there just in case that was exactly what we needed to do. I did not want to try to do the replacement by myself alone; the transmission outweighs me at 170 lbs, and I had little experience. But the shops in Jacksonville were more expensive than Fort Lauderdale, and any parts would have to come from Lauderdale anyway. Plus any major problem would have us in JAX longer than planned. We opted to hold off and do the work here instead. Coincidentally, that had us doing the replacement at exactly 5,000 hours.


Hour meter at change-out. My own ticker rolled over 507,700 the same day.

Disturbingly, while I was calling around for help, several people thought our noises were not necessarily the damper, and at least one mechanic worriedly said it sounded more like bearings. So while in JAX I changed the oil, inspected the magnet and filter screen, and sent an oil sample to the lab. There was no indication of any abnormal wear, and we decided to stick with our plan to change the damper in Fort Lauderdale. With a little extra time on our hands, I found a distributor in the pacific northwest who was selling dampers for $650, shipping included, and ordered it for delivery here.

Once we were in quarters here, had our waste tank empty, and settled into a spot where we could stay put for the duration if anything went wrong, I scheduled the mechanic recommended by Transmission Marine, Greg. The date I scheduled just happened to be my birthday, and I was feeling somewhat old when Greg showed up and turned out to be twenty years my senior. Two old dudes wrestling with a 170-lb transmission.

When we lived in a bus with a cranky old Detroit, every mechanic who knew anything about our engine had gray hair. The great thing about gray-haired mechanics is that they've seen pretty much everything, and I was happy to have Greg's vast experience on board for the project. I had spent much of the previous day removing obstructions like the engine air cleaner, disconnecting the hydraulic PTO and the control cables, and breaking free all the bell housing mounting bolts, removing all but three. I also uncoupled the propeller shaft.

Greg recommended that we simply unbolt the transmission mounts from the stringers upon which they sat, and then slide the tranny back off the engine with it still resting on the mounts. The four bolts holding the two mounts down were rusted and hard to reach, but with two of us we could get a big wrench on each side and get the bolts free. We never even touched the adjustment bolts holding the transmission to its mounts.


Transmission separated and old damper removed. You can see the back of the flywheel. Starboard aft engine mount is at lower right, attached to the bell housing.

Making this whole process much, much easier was the fact that we have four motor mounts in addition to the two transmission mounts. Many marine installations have just two engine mounts, with the aft end of the engine being supported entirely by the transmission itself. We were able to remove the bell housing bolts and slide the transmission back off the engine. We needed a minimum of five inches or so of separation, but we were able to slide the shaft back a good eight inches and we had plenty of room between the cases.

Greg remarked that the flywheel and flywheel bolts were in great shape for 5,000 hours and 16 years. A fine coating of rust dust covered everything, and a small pile of it was at the bottom of the bell housing, which I cleaned up with a shop vac. We needed to do nothing other than slap the new plate on and align the bolts, but in the confined space with a heavy damper this was definitely a two-person job.


Input shaft of transmission showing splines in excellent condition.

ZF has very specific requirements for greasing the splines before assembly, and Greg had to run out to get the proper grease before we could slide the cases back together. The input shaft turns easily by hand and so lining up the splines was relatively straightforward, and with one of us on each side we were able to work the cases back together without mechanical assistance.

The same could not be said for the propeller shaft. We spent a lot of time, and did a lot of head-scratching, to move the shaft forward. Gravity and current had helped us move it back, but uphill was a bigger challenge. Eventually what worked was jamming progressively larger pieces of scrap wood between the coupler and a steel stringer and hammering them straight with a deadblow, while one of us rotated the shaft to break the sticktion. It took an hour.


New damper in place, before sliding cases together. You can see the paint shadow where the transmission mount sits on the stringer.

The bolts and nuts for the transmission mount were in bad shape, as were the studs and nuts for the shaft coupling, and we adjourned to the next day so Greg could pick up new ones on his way home. A combination of Fastenal and Broward Bolt yielded the needed replacements, and the next morning we got the shaft coupled and the mounts bolted back down. Greg got out his feelers and checked the alignment, which remarkably was still dead on after the project and needed no adjustment.

Before we could test we had to have a diver re-set our Spurs line cutter on the shaft; sliding the shaft back meant it would have slid back and rotated wrong-end-down. The diver reported no other issues and gave the hull a quick look-over for our $200 minimum charge. It took all of five minutes.

We did do a brief test in-place while tied to the dock, and we've been down to the pumpout dock and back three times since then and all seems working well. The rattling noise that heralded this project is gone completely, so it was definitely the damper plate and not something more insidious. Greg's invoice was less than a boat unit, and the whole project came in around $1,700. I would guesstimate the cost of having a yard do this work at around five boat units.


The old damper plate. That's rust and rubber dust on the sole which came out the vent holes. I was unable to remove the allen bolts holding the damper together even with an impact driver; I had hoped to see what the damaged rubber isolators looked like.

I had to loosen up the stuffing box to move the shaft, and that will need final adjustment once we are well under way later this month. And I expect the alignment to "settle in," and that may also need another adjustment down the line. But the new damper should carry us another 5,000 hours or thereabouts.