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Old 03-19-2014, 02:05 PM   #1
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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.
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Old 03-19-2014, 02:22 PM   #2
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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.
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Old 03-19-2014, 02:27 PM   #3
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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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Old 03-19-2014, 02:35 PM   #4
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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.
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Old 03-19-2014, 02:53 PM   #5
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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.
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Old 03-19-2014, 03:08 PM   #6
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Yes, as others have said, 24 volt definitely. Since our thruster batteries are "inside" we have AGMs for that use.
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Old 03-19-2014, 03:50 PM   #7
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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.

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.
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Old 03-19-2014, 04:02 PM   #8
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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)
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Old 03-19-2014, 04:09 PM   #9
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... The bow thruster is 12 v/dc...
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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Old 03-19-2014, 04:25 PM   #10
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The yard recommended a Side Power SE100/185T.
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Old 03-19-2014, 05:27 PM   #11
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The yard recommended a Side Power SE100/185T.
That's the one.
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Old 03-19-2014, 05:30 PM   #12
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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.
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.

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Old 03-19-2014, 06:57 PM   #13
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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".
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Old 03-19-2014, 07:06 PM   #14
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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.
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Old 03-19-2014, 07:07 PM   #15
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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.
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Old 03-19-2014, 07:12 PM   #16
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Quote:
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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
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.
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Old 03-19-2014, 07:18 PM   #17
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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.
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Old 03-19-2014, 07:21 PM   #18
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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.
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Old 03-19-2014, 10:10 PM   #19
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Vetus How To Size Bow Thrusters
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Old 03-19-2014, 10:45 PM   #20
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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.
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