Bow Thruster

I recently bought a 42 Kadey Krogen. One of my first projects is to have a bow thruster installed. The yard doing the installation indicated I could go with 12 v/dc or 110 v/ac. Any thoughts on the pros and cons regarding either? Thanks for any input.

I misread the proposal. The bow thruster is 12 v/dc. It was a water pump that was ac or dc. Sorry for the confusion.

A 12v thruster might be a little small for the boat. It will work, but if you have to fight wind and current it might be a little weak. I haven't spec'd one in a while, so a modern 12v might do the job. If not, go 24v. 12v is easier as your boat is probably 12v, and that means a charge link can be set up to engine or house batts. 24v you will need a dedicated charger that will only replenish batts when 120vac is available. That works fine in most cases. Put a dedicated batt right at thruster, don't use other batts in engine room.

We have a 11hp Side power, with two 8d's which are shared with the thruster and windlass and are tied in with the house bank.

Our Sleipner 10HP bow thruster is 24V powered by 2 dedicated 4D's with their own dual 12V charger. Not sure I would go for a simple 12V thruster for a new installation, though our stern thruster is 12V 80Kg Vetus. Many people prefer hydraulics if possible to install retroactively.

Yes, as others have said, 24 volt definitely. Since our thruster batteries are "inside" we have AGMs for that use.

Ski in NC said:

A 12v thruster might be a little small for the boat. It will work, but if you have to fight wind and current it might be a little weak. I haven't spec'd one in a while, so a modern 12v might do the job. If not, go 24v. 12v is easier as your boat is probably 12v, and that means a charge link can be set up to engine or house batts. 24v you will need a dedicated charger that will only replenish batts when 120vac is available. That works fine in most cases. Put a dedicated batt right at thruster, don't use other batts in engine room.

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I would go with 24 volt DC. 12 volt DC may not be enough, and 110 volt ac would have to run a gen set. Also I would install its own battery bank, two 8 D, close to the thrusters with its own charger. Better to have a thruster that is to powerful and not enough.

I question whether you really need 2 x 8D's for the install. We have 2 x 4D's and they provide plenty of power. Only advantage of 8D's would be less need to charge, though we charge our 4D's automatically every time we are on shore power or charging the house batteries by the generator while at anchor. 8D's do not really allow you to run the thruster longer at any one time. Electric thruster use is limited by over heating. No downside to 8D's apart from weight, cost and space!! I do agree with locating close to the thruster since it will typically draw a very high current (350 amps x 12V)

gehales said:

... The bow thruster is 12 v/dc...

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Greg: Congratulations on the KK42.

Side-Power has an 8.4 hp @ 12VDC, dual prop in a 7.28" tunnel, that should work fine for your displacement. We've been looking at upgrading. Ours is 4 hp and is undersized. We tend to dock as if we didn't have one.

The yard recommended a Side Power SE100/185T.

gehales said:

The yard recommended a Side Power SE100/185T.

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That's the one.

Larry M said:

Greg: Congratulations on the KK42.

Side-Power has an 8.4 hp @ 12VDC, dual prop in a 7.28" tunnel, that should work fine for your displacement. We've been looking at upgrading. Ours is 4 hp and is undersized. We tend to dock as if we didn't have one.

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I have that thruster in my boat and will be converting it shortly to hydraulic. 400 amp draw and a sub 1 minute duty cycle are a bad combination. The 24 volt version has a much better duty cycle. The hydraulic is an unlimited duty cycle. Visualize your boat pinned to a wall by the wind and needing to lean on the thruster to get off. Then visualize the over temp kicking out for say 15 minutes. The full version from Side power is pricey. An electric clutch belt driven pump, tank and controls from a yard that specializes in comercial boat hydraulics is actually quite reasonable.

Currently I use mine very little as I fear it kicking out at the worst possible moment. Unless there is a lot of wind, I feel more comfortable relying on my skill, a big rudder with 40+ degrees of angle and my big single screw.

Ted

Size of bank is determined by the thruster. You are much better off using someone like Florida Bow Thruster (in particular). This is what they do, and they service the entire east coast mobility, and have a large facility in Morehead City. Workmanship is superb, you can do a search on them. After the sale support is great, and forever. Much better choice than a yard which may do a handful a year, if that. The very fact they spec'd a 12v unit for a boat that size and weight is a "tell".

Another consideration is cost of installation, parts, labor, batteries etc. vs. price for thruster. I suspect that most of these costs are "fixed" vs. price for thruster unit, so it may make sense to up-size thruster for small additional cost overall.

Size of thrusters is like the horsepower/torque of boat engines.....nobody ever complains about too much horsepower/torque of their engines.

Similarly go with a larger thruster than what the charts call for. We upsized ours from an 8" tube to a 10" tube with a much larger motor. It can really move with bow upwind or against a current. I'm not sure the one called for in the charts would do the job against a strong wind or current.

O C Diver said:

I have that thruster in my boat and will be converting it shortly to hydraulic. 400 amp draw and a sub 1 minute duty cycle are a bad combination. The 24 volt version has a much better duty cycle. The hydraulic is an unlimited duty cycle. Visualize your boat pinned to a wall by the wind and needing to lean on the thruster to get off. Then visualize the over temp kicking out for say 15 minutes. The full version from Side power is pricey. An electric clutch belt driven pump, tank and controls from a yard that specializes in comercial boat hydraulics is actually quite reasonable.

Currently I use mine very little as I fear it kicking out at the worst possible moment. Unless there is a lot of wind, I feel more comfortable relying on my skill, a big rudder with 40+ degrees of angle and my big single screw.

Ted

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I agree. A hydraulic bow thruster is really worth considering. The engine mounted pump replaces the need for extra charging capacity as well as additional storage. I would be surprised if the all up cost wasn't significantly less.
The continuous duty rating is what make hydraulics a favourite for me. For example; In the spring of 2001, I was Bosun on the 280 ton cargo schooner Avontuur that had just delivered a load of timber for the Spirit of South Carolina project in Charleston. We were at the end of the town dock and our bowsprit protruded several feet into a channel that yachts used to access the inner slips. One 40' sail boat was leaving the slips and met with a heavy current that pressed it under our 5/8" chain bobstay. The electric bowthruster cut out three times, just short of freeing him, each time causing more damage as he was pressed back under. A passing dinghy finally carried a line to an adjacent dock to haul him off. This accident, like all accidents, had several contributing factors; current, a timid captain, our bad parking job, and a 30 sec duty cycle on an electric bow thruster.
I have a 33KW vetus hydraulic (44 hp) that requires very little maintenance and had a very reasonable initial cost. I can also use the pump to power my anchor winch. I haven't yet, but that's a project for when it's warmer.

My 24-volt thruster has plenty of power working off the house batteries about 12 feet away.



I'm no less embarrassed to use the thruster than those with twin engines who don't always operate them in the same direction.

FWIT, I merely presumed a 12v system since that is what I have on board. They may well have a 24v system in mind. I'll know more when I get the boat to Washburn's.

OC and Dirk- I agree hydraulic ends up being a better thruster. But I have dealt with poorly connected pump drives to mains and gennies, and that can be real trouble. Also dealt with leaks, makes a real mess in the bilge. For a pleasure boat, a battery powered thruster I think is best. Commercial or heavy duty, hydraulic or engine driven by all means. For OC and his tripping out, that is a PITA that would drive me nuts too. But I don't think all electrics do that. I don't know the longest I've run mine, but it has never tripped.

I really think a hydraulic thruster makes the most sense.. although I did have a Vetus 12v thruster and I never over temp'd the undersized thruster on Volunteer .. and I used it a lot in the locks going up stream on the Columbia/Snake River trip. Most docking in and out of the slip never used more that 30-40 sec. of use per trip.

The big issue with hydraulic is to get the system sized correct so that if it is powered by the main, the main doesn't have to be throttled up to get adequate thrust. The Nordhavn I spend time on has a main pump.. but also a pump on the get home and that is used every time the thruster will or may be called into use.. as a side benefit this gets the get home exercised on a regular basis.

HOLLYWOOD

I have a Dickson hydraulic thruster (stern) and what's nice is it can stay running for as long as I want without worry of anything tripping.
I have run it for minutes at times.
It has been trouble free for at least the 7 years I have owned the boat and no telling how many before that.
Runs off a double V belt off the added pulley on my Ford Lehman 120.

It was most likely tripping because it was too small and underpowered, and possibly using undersized cabling. Another reason to have it spec'd and installed by someone who really knows these things. Yes, like anchors, it pays to go "one up" form the base recommended size, especially if your boat is heavier than normal for its length, and/or has more windage; note how much emphasis Vetus puts on windage.

jleonard said:

I have a Dickson hydraulic thruster (stern) and what's nice is it can stay running for as long as I want without worry of anything tripping.
I have run it for minutes at times.
It has been trouble free for at least the 7 years I have owned the boat and no telling how many before that.
Runs off a double V belt off the added pulley on my Ford Lehman 120.

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Minutes at a time? Wow. I'm curious as to what drives that much use.

15 seconds seems like an eternity; take a look at your watch and imagine the thruster going for that long. Don't think I have run my Vetus for more than 20 seconds (once) and more normally no more than 10 when using it to make an ultra-tight 180. Mostly around 3 or 4 second bursts. It is rated for 2.5 minutes continuous, or also not recommended to exceed that over the course of an hour. I can't imagine coming close to half that.

caltexflanc said:

Minutes at a time? Wow. I'm curious as to what drives that much use.

15 seconds seems like an eternity; take a look at your watch and imagine the thruster going for that long. Don't think I have run my Vetus for more than 20 seconds (once) and more normally no more than 10 when using it to make an ultra-tight 180. Mostly around 3 or 4 second bursts. It is rated for 2.5 minutes continuous, or also not recommended to exceed that over the course of an hour. I can't imagine coming close to half that.

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I have the same Dickson as as j. Minutes? maybe a slight exaggeration on how long we actually use it, but true nonetheless. I think j will agree that it is a bit undersized and mine doesn't have a tunnel around it (that's why we call it 'The Toe Chopper'), so it's NOT the most efficient. Still, it works well-ish and can run for extended periods without worry while it holds the stern to the dock when handling lines. You also are not supposed to operate it over 1000 rpms or it will throw the belts. That's about the only restriction that it has.

caltexflanc said:

Minutes at a time? Wow. I'm curious as to what drives that much use.

15 seconds seems like an eternity; take a look at your watch and imagine the thruster going for that long. Don't think I have run my Vetus for more than 20 seconds (once) and more normally no more than 10 when using it to make an ultra-tight 180. Mostly around 3 or 4 second bursts. It is rated for 2.5 minutes continuous, or also not recommended to exceed that over the course of an hour. I can't imagine coming close to half that.

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A couple of times I left it on to hold the boat against a wind while docking so I could leave the helm and secure lines.
Also sometimes while anchoring to keep the boat in line while backing down letting out rode.

What is the price difference between the DC or Hydraulic? What did the yard quote you? Curious since I'll be doing the same thing in a few months.

-Josh

I don't have a firm price yet. They want to see the boat first. I'm bringing it from Chesapeake, VA to Solomons, MD next week. I'll have more specifics then. They did suggest around 12-14K.

jleonard said:

A couple of times I left it on to hold the boat against a wind while docking so I could leave the helm and secure lines.
Also sometimes while anchoring to keep the boat in line while backing down letting out rode.

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Interesting.

Single screw, single crew boat I take it ?

So your thruster is not far forward, therefor doesn't end up pivoting off the dock kicking the boat's stern out?

I am not sure I understand the anchoring issue. Does your boat easily fall off beam-to when pointed into the wind?

Having anchored out a lot on a variety of boats with thrusters, this use has never occurred to me, so the inquiring mind has been awoken. Have to say ditto about a thruster being able to hold a boat flat to the dock on its own, but then again have never used your particular type of boat. I have seen to it done with both bow and stern thrusters used at once. Even then a total Klutz like me can usually get a spring line on in less than a minute if dealing with cleats and pilings rather than bull rails. I could see where hydraulic stern and bow thruster combo would be awesome. Anyway, always interested in picking up some new tricks, I need all I can get!

Post #22....His is a stern thruster....?......?......