Bow Thruster

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Cigatoo

Cigatoo

Guru
Joined
Sep 9, 2016
Messages
1,872
Location
New England
Vessel Make
Grand Banks 36 Classic #715
We are considering adding a Bow Thruster to our single screw GB 36. Is a pretty much standard 12 volt / 120 volt 30 amp boat. Any thoughts on 12 volt vs 24 volt thruster? Batteries and thruster will be self contained in the bow. So will make for short cable runs.

Also wondering about charging off 100 amp Balmar with an ACR vs dedicated 120 volt battery charger.

Thoughts are appreciated
 
I would go 24 volt. Half the amperage for the same thrust. Lower voltage drop because of less amperage means the motor runs more efficiently and generates less heat.

I prefer the dedicated battery charger if you run a pure sine wave inverter or the generator while underway.

Ted
 
My preference is 12v volt for simplicity. I installed a AGM 12v 2’ from the thruster. It is all stand alone. I added a 10 dedicated amp charger . It is completely isolated from any other system. It moves my 13,k boat with ease. I added a guest battery switch to make for a mechanical disconnect should anything happen.
 
Our NT 37 has a bow bank (two g31 Deka AGM's in parallel for 12V, for both windlass and bow thruster) just a few feet of 2/0 cable from the thruster. Charged by a Blue Seas ACR from the house bank. Simple, works like a charm, and runs the thruster for many seconds with no problem.
 
Arc said:
My preference is 12v volt for simplicity. I installed a AGM 12v 2’ from the thruster. It is all stand alone. I added a 10 dedicated amp charger . It is completely isolated from any other system. It moves my 13,k boat with ease. I added a guest battery switch to make for a mechanical disconnect should anything happen.
Click to expand...


Aside from needing more batteries to make 24V, what would make a 12V version -- as in your installation, and OP's similar bow location -- simpler than a 24V version of the same?

-Chris
 
I am installing a somewhat over sized thruster. The people that I am purchasing it from seem to think that 24 volts is the correct application for that particular thruster. Pricing is the same other then a minimum of 2 batteries for 24 volts. Also a dedicated charger seems best.

Thanks for everyone’s input. .
 
I am putting both bow and stern thrusters on our “new” boat. They are both 24 volt. The only problem is that I couldn’t find any 24 volt Promariner chargers so I had to buy Mastervolt. Our boat was at the top end for 12 volt thrusters and near the bottom end for 24 volt thrusters. The difference in cost was $1000 for both and 2 batteries. To me that was a no brainer to go with the larger thrusters.
 
10000% go 24v. To simplify, just put a small charger dedicated for those batteries up in the bow. Run it through your regular AC. A LOT less cable/config to worry about... But whatever you do, 24v all the way!!! :)
 
Yes, I am putting in 2 24 volt 20 amp chargers, one for bow and one for stern. Much easier than trying to run heavy cables forward.
 
Just make sure that you secure the batteries in the bow really well. I am putting in 2 AGMs and bought some Atwood battery trays. I am using them but am not really impressed with them. The batteries slide back and forth 3/4” which is technically ok by ABYC standards but I don’t want them moving at all so I cut a piece of Starboard to shim the tray so the batteries don’t move at all. Also the top that holds the batteries down is flimsy so I added a piece of Starboard across the top to hold the batteries down. And I will be through bolting the trays instead of just screwing them down.
 
Comodave said:
Just make sure that you secure the batteries in the bow really well. I am putting in 2 AGMs and bought some Atwood battery trays. I am using them but am not really impressed with them. The batteries slide back and forth 3/4” which is technically ok by ABYC standards but I don’t want them moving at all so I cut a piece of Starboard to shim the tray so the batteries don’t move at all. Also the top that holds the batteries down is flimsy so I added a piece of Starboard across the top to hold the batteries down. And I will be through bolting the trays instead of just screwing them down.
Click to expand...

NICE! Those def aren't moving! Mine are also through-bolted. I used foam from gym floor mats on my outside edges. Piece of duct tape on one side makes sure they dont move and I can use a smaller piece 2"x2" square. Keeps them secure but also doesn't "insulate" them and keeps a buffer of air around the batteries. Also keeps the batteries from having any sort of "abrasion point" since they will def. get some motion in the bow from waves, but also micro-vibration... :)
 
Just be sure to read the use booklet before buying a thruster.

Many are very very limited in terms of operating time ( in seconds) vs cooling time.
 
While I understand the reflex to recommend 24v, much depends on geometry- bear in mind,, this is a 36 foot boat. For my Willard 36, I went the 2x12v AGM parallel (12v) route. Distance from forward batteries to thruster is under 5-feet. Also powers existing 12v windlass. My house bank is LiFePO4 so have a DC-DC charger for the AGM banks. While I have a generator, it is used only occasionally. Powering a 120vac charger would be problematic. While going 24v reduces cable complexity for the thruster, keeping 12v for the windlass cables increases length and complexity there. For a new build, would go 24v both windlass and thruster.

And let's not forget that the GB36 is a pretty mannerly boat. I would not expect it to require excessive amounts of thrust.

Regardless good luck with the install. I happen to like thrusters. Anything that makes a boat easier to use is good value.

Peter
 
ranger42c said:
Aside from needing more batteries to make 24V, what would make a 12V version -- as in your installation, and OP's similar bow location -- simpler than a 24V version of the same?



-Chris
Click to expand...
I would think charging is the biggest consideration for simplicity. AC chargers are one thing but what about when you are cruising away from dock and don't want to run gennie to get back to 100% charge.
DC to DC charger may be the simplest as how ever you charge house or start it then takes care of the thruster.
Just remember that AGM need to be brought back to 100% SOC at least periodically (several days to week).
Cable size a Neg w 12V but with short runs not a big deal.
 
Arc said:
My preference is 12v volt for simplicity. I installed a AGM 12v 2’ from the thruster. It is all stand alone. I added a 10 dedicated amp charger . It is completely isolated from any other system. It moves my 13,k boat with ease. I added a guest battery switch to make for a mechanical disconnect should anything happen.
Click to expand...

ranger42c said:
Aside from needing more batteries to make 24V, what would make a 12V version -- as in your installation, and OP's similar bow location -- simpler than a 24V version of the same?
Click to expand...

Bacchus said:
I would think charging is the biggest consideration for simplicity. AC chargers are one thing but what about when you are cruising away from dock and don't want to run gennie to get back to 100% charge.
DC to DC charger may be the simplest as how ever you charge house or start it then takes care of the thruster.
Just remember that AGM need to be brought back to 100% SOC at least periodically (several days to week).
Cable size a Neg w 12V but with short runs not a big deal.
Click to expand...


Arc said his is an isolated system, with it's own nearby battery and charger... and his preference for "12 volt for simplicity." Sounds like a good set-up, but...

I just wondered what would make 12V simpler than 24V in a similar isolated system -- own battery bank, own charger -- aside from having to add battery to get to 24V.

-Chris
 
O C Diver said:
I would go 24 volt. Half the amperage for the same thrust. Lower voltage drop because of less amperage means the motor runs more efficiently and generates less heat.

I prefer the dedicated battery charger if you run a pure sine wave inverter or the generator while underway.

Ted
Click to expand...

Thumbs up. Having run a GB36 extensively, I wholeheartedly agree with adding a BT. 24V for the isolated system you propose would be good because the GB is not a light boat, and 24V would drive a smallish BT harder than 12V power. Do you foresee any need to charge the 24V system underway? I would think not.
 
Last edited:
ranger42c said:
Arc said his is an isolated system, with it's own nearby battery and charger... and his preference for "12 volt for simplicity." Sounds like a good set-up, but...



I just wondered what would make 12V simpler than 24V in a similar isolated system -- own battery bank, own charger -- aside from having to add battery to get to 24V.



-Chris
Click to expand...
Wasn't clear if only recharges at the dock or when gen runs. I am glad I charge mine while underway using a charge relay... easy w 12V requires another charger (DC TO DC) if 24V
 
rgano said:
Thumbs up. Having run a GB36 extensively, I wholeheartedly agree with adding a BT. 24V for the isolated system you propose would be good because the GB is not a light boat, and 24V would drive a smallish BT harder than 12V power. Do you foresee any need to charge the 24V system underway? I would think not.
Click to expand...

IMO, it's too easy to have recharging underway, not to do it. Performance is always better with maximum voltage (fully charged battery).

Ted
 
Our last boat had a stern thruster and we only charged the battery when we were on shore power or had the generator running. We never had any issues with the battery being discharged. You only run the thruster for brief times.
 
"And let's not forget that the GB36 is a pretty mannerly boat. I would not expect it to require excessive amounts of thrust."

I have been handling the boat quite well if I do say so myself. The boat does handle well when backing down. Proud of the fact that I didn't need a bow thruster to back in and out of a gnarly slip. Then we closed in the fly bridge. :facepalm: Like flying a big spinnaker. LOL

I am putting in a bow thruster designed for boats from 39 to 48 feet. Should be over kill. Price is pretty much the same. Regardless 12 or 24 volts I will put in 2 batteries with an isolated ac charger that the Mastervolt inverter / 100 amp Balmar will easily run.
 
I always go with one size larger thrusters. The cost is not much more abd then you will have the extra power forever. Nothing, much, worse than putting in a thruster at great expense and work to find out it doesn’t work well when the wind blows.
 
Cigatoo said:
"And let's not forget that the GB36 is a pretty mannerly boat. I would not expect it to require excessive amounts of thrust."



I have been handling the boat quite well if I do say so myself. The boat does handle well when backing down. Proud of the fact that I didn't need a bow thruster to back in and out of a gnarly slip. Then we closed in the fly bridge. :facepalm: Like flying a big spinnaker. LOL



I am putting in a bow thruster designed for boats from 39 to 48 feet. Should be over kill. Price is pretty much the same. Regardless 12 or 24 volts I will put in 2 batteries with an isolated ac charger that the Mastervolt inverter / 100 amp Balmar will easily run.
Click to expand...
As an aside, I used to teach close quarter maneuvering. One guy - a retired electrical engineer - hired me to teach his three adult sons/son-in-law to drive his GB36 classic with single. I did a two day seminar with them and they had so much fun that their wives insisted on a class for them, so I did a repeat. It was so easy to teach on that boat - it just responds so well.

To my mind, the GB36 single screw is thr gold standard of trawler-style family cruiser yachts. Even with so many imitations, the GB really stands out. There is a certain zen about them. The size is large enough for a family yet small enough to be approachable.

Good luck Cigatoo

Peter
 
mvweebles said:
As an aside, I used to teach close quarter maneuvering. One guy - a retired electrical engineer - hired me to teach his three adult sons/son-in-law to drive his GB36 classic with single. I did a two day seminar with them and they had so much fun that their wives insisted on a class for them, so I did a repeat. It was so easy to teach on that boat - it just responds so well.

To my mind, the GB36 single screw is thr gold standard of trawler-style family cruiser yachts. Even with so many imitations, the GB really stands out. There is a certain zen about them. The size is large enough for a family yet small enough to be approachable.

Good luck Cigatoo

Peter
Click to expand...

Agree on the handling. Is very predictable. Especially when backing down.
 
We had a DockStar Smart Thruster on both bow and stern of our CHB 34 - easy to install yourself, no extra batteries or wiring and all the power we needed to spin the boat on a dime. It will hold you up against the slip while you tie off as well. Recommend highly!

https://www.dockstarthrusters.com/
 
Cigatoo said:
I am installing a somewhat over sized thruster. The people that I am purchasing it from seem to think that 24 volts is the correct application for that particular thruster. Pricing is the same other then a minimum of 2 batteries for 24 volts. Also a dedicated charger seems best.

Thanks for everyone’s input. .
Click to expand...

This is what I did as well. Two Group 31s and a 24v charger. I chose AGMs. The other day I had to spin our boat off a dock with challenges fore and aft. I did have dock help to be sure the stern did not hit but I had to power against the wind and a small current about 320 degrees. No problem, plenty of power and battery.
 
A 12volt Sidepower will be more than enough for a 36 GB. I've been using mine on a 41ft, 35,000lb boat for 6yrs and use it extensively.
 
That's the SE 100/185T Sidepower unit.
 
We just installed on our 1988 Californian 48 CPMY bow and stern thrusters and while we were at it, replaced the old windlass. We have a lot of canvas at the top, so all (myself and the boat yard) were concerned about windage. I'm of the mindset in doing it right the first time. So, we went with the largest thrusters that would physically fit, and ended up with Side-Power SE 170's, 24 volt. The 24 volt tied into the new Lofrans 24-volt windlass.

Two new 12-volt batteries forward, and two aft. Since the battery charger was probably the original, we replaced that with a new Sterling Power charger. To charge the thruster/windlass batteries, we installed two Sterling Power DC - DC chargers. On top of all this, we installed two new Balmar alternators, two regulators, and a Centerfielder.

Overkill, yes, and the project started in my mind as "simply" installing a bow thruster. But, hey, that's what boats are for. Plus, we hope it will facilitate the next upgrade which will be installing two new engine start batteries and using all four 8D's as house (currently one is port engine start, the other three starboard start and house).

One thing on the thruster controls. Since the controls are through CanBus and easy to install, I put one control on the port side and one on the starboard side in the upper helm. Close-in visibility is an issue for us.

With the bow and stern thrusters, I can slip in sideways into our berth. That really reduces the pucker factor when there is a megayacht berthed in front of us. I would really hate to nick one of them.
 
Mike H said:
We just installed on our 1988 Californian 48 CPMY bow and stern thrusters and while we were at it, replaced the old windlass. We have a lot of canvas at the top, so all (myself and the boat yard) were concerned about windage. I'm of the mindset in doing it right the first time. So, we went with the largest thrusters that would physically fit, and ended up with Side-Power SE 170's, 24 volt. The 24 volt tied into the new Lofrans 24-volt windlass.

Two new 12-volt batteries forward, and two aft. Since the battery charger was probably the original, we replaced that with a new Sterling Power charger. To charge the thruster/windlass batteries, we installed two Sterling Power DC - DC chargers. On top of all this, we installed two new Balmar alternators, two regulators, and a Centerfielder.

Overkill, yes, and the project started in my mind as "simply" installing a bow thruster. But, hey, that's what boats are for. Plus, we hope it will facilitate the next upgrade which will be installing two new engine start batteries and using all four 8D's as house (currently one is port engine start, the other three starboard start and house).

One thing on the thruster controls. Since the controls are through CanBus and easy to install, I put one control on the port side and one on the starboard side in the upper helm. Close-in visibility is an issue for us.

With the bow and stern thrusters, I can slip in sideways into our berth. That really reduces the pucker factor when there is a megayacht berthed in front of us. I would really hate to nick one of them.
Click to expand...

Sounds like a good plan, but why stick with 8Ds for the house? Lots of better choices for house batteries.
 
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