TravelTalkOnline Forums Travel and Vacation Forums British Virgin Islands Tell me about Bow Thruster Usage

For my upcoming charter, the boat I will have (Moorings 46.3) will have bow thrusters. I've never used bow thrusters so I was looking for some tips and tricks and do's and don'ts.

I've read various snippets about them but it sounds like, in general, they tend to be finicky about being used too long. It sounds like if you use them for more than a couple minutes at a time they might burn out (or at least trip a breaker?). Is this true? It sounds like a terrible design flaw if so. I'm not terribly worried about this I suppose - since I've never used/needed them in the past. On the other hand, this a slightly bigger boat than I've chartered in the past (and there's a reason they are there...).

So, any insight into that aspect of it would be helpful.

Next, and please don't kill me for asking this but, I was wondering about whether it might make sense to use the thrusters when picking up a mooring. My reasoning is that approaching a ball at slow speed means not much water past the rudder and therefore less steerage and more tendency to get blown off to either side as you approach. Could I just keep the rudder straight and use the thruster to change direction and keep my bow pointed at the ball? Can you effectively steer with the thrusters?

Now, I've never heard of this, which makes me think it's probably a stupid idea for some reason, but - again, not knowing anything about them - it SEEMS like it could work. Also, I don't normally have a problem picking up balls so I don't really need a different solution I guess but there certainly have been times when the wind is strong and swirling where I've had to reset, drift back and try again.

Thanks!

There really isn't any situation that i can think of that would require running the bow thrusters continuously more than a few seconds. Even if you were holding the bow in a wind it would likely be bursts of use.

As far as picking up mooring, you will still approach to a stop using the rudder, but if you miss the pendant a little or the bow starts to blow off the thruster is a great alternative to going around :-).

Better to ** trip a breaker** than burn out your bow thruster.
learning the times using a thruster in short bursts -- maybe in concert with the prop -- docking - mooring you can find when it is effective

Sure but what's the limit? How much rest time do I have to give it? Do I have one shot to put the bow back on the ball and if my crew misses the pendant I don't dare hit the thruster again because it hasn't rested enough?

And more importantly, why is this even a thing? Can the motor just not cool itself? Why can't it handle more than a few seconds of continuous operation?


Why is it so easy to burn out your bow thruster? It just doesn't make any sense to me. Regardless of how much I *should* need it, why will it break if I use it too much?

It is not recommended to use a bow thruster when picking up a mooring. A mooring penndant can easily be sucked into the thruster. This could be a costly call to the charter company. Much better to back off and go around.

@txmsails - bowthrusters draw a lot of electric power, a larger boat will have a 16HP motor that draws around 12,000 watts. At 24V that is a whopping 500 amps. Not only does the motor heat up, but so do the batteries and cables producing and carrying that load.

My bowthruster is relatively deep and far back. I singlehand and use it for fine adjustments when approaching a mooring, as the rudder has no effect when I'm that slow. That allows me to easily pick up moorings alone without any stress. I also use the bowthruster when leaving a mooring or anchoring spot in tight conditions. Even at low speed it makes my turn radius much, much smaller.

I use 1-2 second bursts, that is enough to move my bow 10-20 degrees. When I dock I prefer to back in. I will line the boat up and center the wheel while about a boat length away and use 1-2 second bowthruster bursts to steer. Sometimes with a strong breeze I'll need to move the bow against the wind and that will entail 5 or more seconds. All of that is well within the design specifications.

The longest I've used one was several bursts of 10-15 seconds over a couple of minutes (I was waiting in the channel at the St. Martin drawbridge and a boat ahead of me had stopped and the boat behind me was too close, and the wind was blowing me towards the rocks) and it stopped working, it was a thermal fuse as it later worked again when I'd anchored and wanted to fix the problem.

I wondered about this. Are there not screens on the intake ports that would prevent this? If not, I agree this would be a good reason to not use it and even if there are, I can see where you still might not want to risk it. Hmm.


This makes sense - thanks for pointing this out. Still feels like a bit of a design flaw to me...


Cool! At least this helps me not feel like a total idiot for thinking about this


Yikes! That sounds terrifying. I guess you manage to keep her off the rocks!

Mooring pennants are relatively thick lines with a float at one end and attached to the mooring at the other. The bowthruster channel is below the surface, so it cannot pick up either end. I have a big bowthruster with a 25cm diameter (10 inches). It is very difficult (polite phrasing for "impossible") for the typical BVI pennant to naturally bend at 180 degrees in a 10 inch radius and get sucked into the bowthruster tunnel. Bowthruster tunnels generally do not have screens - they really are not needed. Smaller boats have even smaller diameter bowthruster tunnels (6-8 inch) and they could only ingest an end of a line, not a loop in one. Plus if you aren't alone you'll have someone on the bow and I recommend using hand signals rather than voice. Have them point left for you to move the bow left, and point forward to move the boat forward and make a fist straight up for you to stop the boat. And a happy thumbs up for having attached the boat to the pennant on a cleat, letting you go forward to either approve their efforts or clean up the attachment. If there's a chance of ingesting a pennant while picking up a mooring, they would just use the appropriate hand signal to stop. I've been using that method with uninitiated newbies on crew for years and we have rarely missed a pickup.

A bowthruster is a wonderful tool which makes lots of close-quarters actions much, much easier. If you have one, use it!

I am only going by what I've been instructed by BVI Yacht Charters and Conch Charters during boat briefing. I certainly don't have the sailing experience Arnd has,but I'll continue to do as instructed by the charter companies. The Admiral is pretty good at picking up a mooring anyway.

We chartered a 46.3 in 2022, as well as a 45.3 a couple of years earlier both with bow thrusters. I found them to be indispensable in several situations.

One is, if there isn't a strong wind blowing, to simplify position keeping while the crew picks up and secures the pendant. When leaving the mooring, a quick burst is a good way to get the bow away from the release pendant to minimize any chance of the boat drifting over the pendant.

Second is when backing into a slip. I've done that both with and without a bow thruster and, perhaps I'm admitting to limited backing skills with a large mono,I found it much easier, matter of fact downright simple to back in with short bursts of power followed by a short burst of the thruster to counteract any propwalk.

There are limitations. I used them a lot on the last charters and never had a situation where the pendant was getting close enough, or deep enough, to get sucked into an intake. Can't say I ever investigated it, but I can't image an intake large enough to suck in a typical pendant. If you keep the bursts short and have good awareness of pendant location, this should not be a problem

Short bursts for sure. There was a case (backing into an east facing slip at Oil Nut Bay with 15-20 knots at about 30 degrees off the bow blowing me off the slip) that they can't counteract and my efforts to do so with the thruster tripped the breaker. We got into the slip (thanks to the dock hands using our dinghy as a tugboat to push the bow), let the thruster cool down, reset the breaker and all was fine.

As an aside, we absolutely loved the 46.3. First charter where we had a genset and A/C (14 charters all monos). Be sure to get a good briefing on the electronics. My son and I both have degress in computer science but it still took some time to figure it all out.

Thanks, this is great info!

Glad to hear about the 46.3. Yeah, this will be my first with genset and A/C (beyond dockside). I remember looking down my nose at those hotdog cats who were running their A/C at anchor while we were "doing a REAL charter" and just dealing with the warm temps. Now that I'll have one, it's going to be interesting whether I'll give into the pampering or stick to my guns and rough it like a good sailor should. :-)

I'm going to try and resist - wish me luck!

Thanks all, for this discussion. Very helpful.

The heat never bothers me down there, but having the AC running and avoiding the 2am "close the hatches because it's raining" drill had us using it every night. Also the aft cabins have poor ventilation unless you keep the doors open which of course means a certain amount of loss of privacy.

We had an issue with one of the compressors cutting out due to a plugged water intake line. The fix is easy once we talked to the mechanic over the phone about location of the compressor and procedure for flushing. You might want to have them identify this for you before departure.

Fair winds! I'm a bit jealous because we were thinking about a 46.3 charter in late June but it doesn't look like that will come together this year.

Ha! Yes, the close/open hatches dance with the rain is a killer!

This will be the first time with other people on board (in the aft cabin - I'm the skipper. I'm taking the bow!) so yeah, privacy could be a concern.

Great points. Thanks.

I don't know if it needs to be said because it probably comes up in briefings, but it didn't in ours: on the boat we had you needed to push both buttons simultaneously to turn it on prior to use. I only had one situation where I would like to have used it, wind on to the dock on a side tie leaving the dock.

Couple additional things….

1 - lines can definitely be sucked into bow thrusters. Keep them clear while mooring or docking. I’ve seen it happen twice to other boats.

2 - if the thrusters overheat or shut down for any reason they can usually be reset by cycling the batteries. Had it happen to me on a Beneteau 50 when I was coming in to Angel Island docks with a stiff current.

3 - most thrusters have an automatic shut off after 5 mins or so. Make sure before you come in to dock they’re on and awake.

Some people think it’s cheating to use them, but on a boat > 50ft they are invaluable for docking in tight spaces.

Just looking for opinions from those who use bow thrusters on monohull sailboats. My wife and I live aboard our Lagoon 42, so no need for or personal experience using bow thrusters.

We have good friends with a 38’ monohull. They are occasional sailors, they probably take their boat out less than 3x per month, mostly day sailing, with trips of 2-3 days in the sound from time-to-time. Their procedure for using the bow thruster is the wife operates it by remote at the bow while the husband is at the helm.He doesn’t “call out” instructions, she simply uses the bow thruster when she thinks appropriate. My wife and I have been onboard when they hit a dinghy on davits on another boat, backed into a dock and their wind generator blades hit a piling, and numerous “bumps”, some pretty hard into docks and pilings. I attribute most instances I’ve witnessed to improperly using the bow thrusters.

I’ve never seen any other boaters share the helming responsibilities that way. Do others do it in a similar fashion and I’ve just never noticed? I’ve thought about bringing it up with my friends, but they think their way works “great” (their word). I guess it’s none of my business but it doesn’t seem like good seamanship.

Holy cow OceanSong. Where do they sail?

Mostly in the sounds of North Carolina.

Try touching fingertips with someone else. It doesn’t work well when you are both trying. That’s what they are doing.

We boat in the great lakes on a 60' power boat - with both bow & stern thrusters. Think of the thruster as a little nudge - toggle it on for a second or two & see if that moves the boat where you want. If not, toggle again for a few seconds. No need to flip it on and leave it on - unless you're in some serious winds and it's the only way to move the boat side ways - like docking and needing to get the boat over to the dock.