Help with thruster installation cost

#1
For purposes of the cussin and dis-cussin going on in our group of owners, I appeal to the wiser heads found here. Does anyone have any info, or an educated guess, on the cost of retrofitting tunnel drive bow thrusters into a Summerset mono-hull? Parts, labor etc. Many thanks in advance.
 

Endurance

Well-Known Member
#2
I am guessing that you will need an aluminum tube that goes from one side of the boat to the other. If you could get by with something as small as 8" inside diameter, that could be had at a place like Utah Tank and Trailer in Salt Lake City for under $200. I would figure about a day of welding to put the tube in place and support the inside of the tube near the center, so I would budget $800 for labor. Depending on what you need to put the thruster in place in the tube, you could likely have the physical mounting done for a total of about $1,500. This assumes you don't have to move anything inside your hull to make room for the tube to go side to side.

You will also need to make provision for powering the thruster. Let's assume that you're buying a 12 volt 4 kw unit. About this time, you would want to grab a calculator and divide 4,000 watts by 12 volts to get 333 Amps. If the thought of something drawing 333 Amps doesn't give you a little pause, it will. A 333 amp draw is more than most starer motors draw. For a starter motor, a massive power draw isn't that big of deal because engines usually start in five seconds or so. To get much good out of a thruster, you will need to plan on maybe 3 or 4 minutes of battery-zapping draw rather than 5 or 10 seconds.

Most people have a dedicated battery bank that they mount fairly close to their thruster. You will need to size your battery bank to cover all of the thruster use you would need for the next 5 or 6 hours because it literally takes hours to put that much power back into a battery bank. You might get by with a bank of 6 golf cart batteries. I would be more comfortable with something like 6 L-16 batteries. If you want AGM batteries, a set of 6 L-16 batteries will run about $2,500. If you can live with the maintenance needs of wet cells, you can cut that battery cost in half. You can save even more by using golf cart batteries, but you will limit your thruster use to a minute or two every 5 or 6 hours.

You will probably want 0000 (pronounced four-aught) battery cable between your battery bank and your thruster. It's about the size of a small garden hose. If you can mount your battery bank reasonably close (meaning less than 10 feet) to your existing inverter/charger (I am assuming you have one of those), you can let that charge your batteries. If not, you would need to buy a decent 3 or 4 stage charger. Something like a 90-Amp Iota will run you about $225. The 0000 battery cable isn't cheap, but someone like Greg's Marine Wire Supply would be able to build tinned copper cable for you. I would budget $300 or so for the cables.

So turning my seat of the pants guesses into an overall wild guess, I would plan on $5,000 installation for your thruster. But that's a wild guess. As an example of price swings, it is kind of a fluke that you can buy 8" aluminum tube for $200 because that is the size that tanker trailers use to hold their hoses along the side of the trailer. If you needed 10 inch tube, you might be buying schedule 40 aluminum pipe from someone like Tube Service in Denver. If you bought 15 feet of that, your tube cost would increase to over $1,000 plus about $150 for shipping if you don't live close enough to one of their yards in Denver or So Cal to pick it up yourself.

Hope this helps.
 

Endurance

Well-Known Member
#4
Just to be sure you are already using a more simple approach, do you have Propco props? Propco makes reverse-cup props that they claim will double reverse thrust without hurting forward thrust at houseboat speeds. A friend of mine (an engineer by trade) did some testing with his boat and found that, if anything, the claim of 200% reverse thrust was understated. If you haven't done it already, I would drop $400 for a pair of Propco reverse-cup houseboat props and give it one more season.

The Propco props aren't be-all end-all, but I would surely try them before I considered a thruster.
 

davew

Well-Known Member
#7
also keep in mind that the new "tunnel" that endurance is talking about needs to be welded inside the current hull-- given that you are looking for bow thrusters, it can not be mounted under the hull, because you would rip it off the first time you beached the boat --- so to get the "tunnel" in the right spot, the fabricator would need to cut a 12" wide, by 4 foot long ( estimate) hole in your hull --- weld in the sides of the new hole, attach the tunnel, and button all of this back up. This would allow the bottom to continue to be "flat" --
you could also power the thrusters by a hydo pump off of your generator -- this is how most new ones are done. you would still need the welding done. a place to start looking for the supplies is www.thrusterman.com -- I have spoken with him in the past, and he really knows his stuff.
as far as the reverse cup props -- my opinion is that every houseboat should have these-- they work great
 
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