Mostly successful docking despite runaway bow thruster

There’s probably no good time for a bow thruster to get stuck in ON mode, but it happened to me while backing into our marina slip on a windy day. Moreover, that maneuver included a 90-degree turn with numerous nice boats tied up close by and rocky shallows not far downwind. While the cause of the thruster failure turned out to be minor, the possible perils and the lessons learned were not.

After a successful weekend of testing our new LiFePO4 batteries, I noticed the winds picking up and decided to head for our B Dock slip deep inside Legacy Harbour Marina. By the time we’d reached the three-legged entrance channel, the southwest winds were gusting above 25 miles-per-hour, which is perpendicular to our slip and also meant we’d be pushed sideways toward a fairly close and unprotected seawall.

But no big deal, I thought; I’ve docked in winds like this plenty of times. While our Carver Voyager 570 Have Another Day may have lots of windage with little keel mitigation — see my Seakeeper install entry for more detail — she also has two 675 horsepower diesel engines plus 24-volt bow and stern thrusters.

So as we reached the end of the last fairway — seawall dead ahead — I maneuvered to starboard so the boat could be blown to port some as we did our 90-degree backing turn into the slip. I tapped the bow thruster to starboard a bit, but when I heard a thruster running without my hand on the control, I looked around wondering who else was maneuvering their boat so nearby.

But it was my thruster stuck to starboard even though the control stick was in the straight-up neutral position when I checked it. I also turned off power to our Dockmate remote control system in case it was the culprit, but it wasn’t. At this point the boat is barely moving — the thruster helping against the wind (though I don’t think I’d really processed this) — but things were quickly getting out of control. My first thought was to pull out of the marina and assess our options, and that’s the plan I communicated over our headsets to Laura, who was on deck ready to handle lines with the girls.

The more I thought about it, the more it seemed like a bad idea to maneuver back through a marina full of boats with both a thruster and wind pushing the boat around. The better choice, I decided, was to immediately stuff the boat into the slip as best we could, and it was great to then realize that I could stop the thruster by pushing the control stick to port.

So I got my daughter Molly — who recently finished her Florida boating safety course — to come up and hold the stick over while I attempted to dock. But as I backed in, the wind pushed the bow towards shore and my neighbor’s beautifully maintained Tollycraft, and so I tried to correct with more reverse starboard engine throttle meant to pull the bow to port. Unfortunately, the stern was already pretty close to the floating dock, so the added speed mainly meant that the swim platform hit it harder.

The bad news was some damage to the platform. The good news was how we’d gotten most of the way into the slip with the port bow laying on the center piling and the starboard stern against the finger dock. We were then able to use the engines and dock lines to walk the boat into her correct position and get her properly tied up, all in a fairly calm manner.

What went wrong? Plenty!

With Have Another Day safely back in her slip, it was time to assess what happened. First, though, I learned that a marina dockhand had attempted to fend off the stern with his hands, which meant dropping his end of a stern line into the reverse suction of our starboard propeller. Fortunately, the prop instantly cut the line instead of wrapping it.

Also, once we were tied up, I had Molly let go of the thruster control and it immediately thrusted to starboard again. So I turned off its battery switch in the engine room, and that’s when I began to figure out that the problem must be in the solenoid.

It took me a day to cool off enough for diagnostic work, but finding the culprit was quick. I took the photo above by sticking my phone into a floor hatch above the thruster and blindly snapping away. What I was then able to see was that one contact stuck in the up position. Fortunately, the solenoid is a readily available off-the-shelf part, a huge relief because Volvo-Penta stopped making Have Another Day’s QL bow and stern thrusters quite a while ago and stocks no spares.

When I fully removed the failed solenoid, I discovered evidence of sustained arcing on the contacts, most noticeable on left in the photo above. I believe that the arcing effectively tack-welded that contact in the closed position so it did not spring back to the open position when I released the control. Once removed, I could easily break the “weld” free and the solenoid now seems to work normally. But it will never see service again, as the arcing build-up makes it a ticking timebomb for another failure.

Failures at the helm

This entire episode was a reminder of how quickly things can go wrong and how difficult it can be to make good decisions in the moment. The first realization I had — after we were tied to the dock and the damage was done — was that the thruster was actually stuck to starboard, which would have fought the wind had I asked Molly to release the stick. But in the moment, I just knew the thruster was broken and wanted it stopped.

Also in hindsight, I wondered if I should have tied the boat up at an easier berth elsewhere in the marina. But I’d decided to maneuver as little as possible because I didn’t know if the thruster “solution” was stable or if its motor would suddenly turn back on, or turn on in the other direction, or otherwise surprise me. And I still think this was the right decision. I saw a path to getting safely tied up and it seemed the least risk to the boats around us. Ideally, I’d have loved to get back out on the river, drop the anchor and assess; but that trip would have had us passing hundreds of boats in narrow fairways with two 90 degree right turns and a 180.

In challenging winds I typically try to maneuver into the wind so that I can control the boat’s movement with the main engines. Unfortunately, my slip’s orientation and the day’s wind direction didn’t leave that option available. Also note that it’s only 40 feet from the land side of my slip to the mangroves and rocks. With a boat nearly 60 feet long, I didn’t have the room to go past my slip and head into the wind before backing into the slip.

Overall, I think the biggest mistake was violating my number one docking rule: never approach one any faster than you want to hit it. But the boat wasn’t responding as I wanted it to and, in the stress, I applied too much throttle and thus hit the dock faster and harder than I would have liked. The swim platform paid the price, but I’m okay with the outcome overall. The damage is relatively easily fixed and the only my boat was hurt.

So I guess I’ll be content with a bit of wisdom from Chuck Yeager: If you can walk away from a landing, it’s a good landing. If you use the airplane the next day, it’s an outstanding landing. I’ll call this a good one, dust myself off and get back on the water.