Bow Thruster vs Stern Thruster

[BruceK]

I can see the point of developing and retaining "no thruster handling skills', you never know when you`ll lose one(see post 150 above). But if there are useful aids to handling, like thrusters, it`s hard finding non financial reasons to refuse having or using them. As the late Aussie PM Malcolm Fraser was fond of saying, "life wasn`t meant to be easy". Neither was it meant to be harder than needs be.

 

[Nickair]

I can see the point of developing and retaining "no thruster handling skills', you never know when you`ll lose one(see post 150 above). But if there are useful aids to handling, like thrusters, it`s hard finding non financial reasons to refuse having or using them. As the late Aussie PM Malcolm Fraser was fond of saying, "life wasn`t meant to be easy". Neither was it meant to be harder than needs be.

Well said. Your words above do make good sense.

 

[Beaverlake]

So Drew from the Bayliner Owners Club invites me out on his bow and stern thruster equipped 4788. He and I went out on his 4788 today for a brief, yet instructional “cruise”.

The wind was light and northerly. Drew’s slip is oriented more or less N/S, stern in, bow facing south. His entryway is narrow, not much wider than his LOA.

Drew used transmissions and stern thruster only to exit his slip. The breeze was behind the boat. Using fwd/rev “twist” and the stern thruster he was able to maneuver within the constrained area and not only his slip but also his “lane”.

We continued westbound toward a fuel dock under a freshening breeze that was variable in direction by 5-10 degrees and “on the nose”. He maneuvered parallel to the dock with the bow leading and used the stern thruster to tuck in the stern.

It was clear that in these conditions the difference in assist between bow thruster only and stern thruster only was negligible. In windier conditions or in the presence of a strong current - YMMV. Our boats have almost no keel, twin engines, and soft chines. It was fairly clear that an assist from either end would result in a pivot at about the same spot fore and aft. Some conditions might favor a thruster at one end or the other; however, that advantage could be offset if a different approach was possible.

We could have stayed out for a much longer time testing every possible combination and permutation but it didn’t take long for both of us to reach the same conclusion that any advantage from one or the other is an “it all depends” answer even with the same hull. Proficiency, wind, current, etc. would probably have more impact than thruster location. If a bow thruster was 20%-30% more expensive then for any number of reasons (like resale) I’d spend the added amount. But after our empirical testing, in my opinion a bow thruster does not give a 1.5x or 2x advantage. I can also state that for me - although a thruster is no substitute for skills, prep, intelligent use of fenders and lines, etc. - I do miss having the extra security in close quarters boat handling provided by a thruster.

 

[Comodave]

And you can easily install the stern thruster yourself and save a bundle. Probably about $5K total. If you have any questions about DIY install PM me and we can get together on the phone and go over it.

 

[TWedd]

Good information and well presented. I've been following this thread as I am considering some combination of thrusters myself. Thanks!

 

[TWedd]

You should look at the Dockstar Thrusters. We have a 34' CHB and they work great. The motors, batteries, radio, control electronics, and mounting rail are all in one compact unit. It is mounted using a T-track on a stainless tube. They are remote controlled so you can walk around the boat, even down onto the dock while docking. They are a fraction of the cost of the regular thrusters. You can also install them yourself. No need to be in dry dock.

I've been looking at these, and am interested hearing more from those that have them. Does anybody else have experience with them, or know those that do? Laurie, Do they seem to have enough power for your needs? I talked to the owner/designer of Dockstar, He seemed to think my 40' Trawler was at the upper limits of his product and felt I would need both bow and stern applications.

 

[Comodave]

The one thing that I learned about thrusters is that you don’t want a thruster that is not big enough. I went oversize on mine and do not regret it a bit. The cost differential was not much but it is well worth it when the wind blows hard.

 

[jointcustody]

Laurie,

I recently purchased a CHB 34' and we are seriously looking at a dockstar stern thruster. Do you have both bow and stern? do you recommend one or the other? Just looking for one for now. Does one have enough thrust on the stern for docking? Thanks.

 

[MYTraveler]

You should get two types of responses, those who prefer bow thrusters and the rest that prefer stern thrusters.

My response is a little different -- I believe that with a bow thruster on a twin screw boat, a stern thruster is not necessary to move the boat straight sideways or in any other direction. I don't have a stern thruster and wouldn't use it if I did. Conversely, without a bow thruster it is difficult (and in some common wind/current conditions impossible) to move the boat sideways -- you can't get enough leverage on the boat from the two props and rudders that are so far back. So, if you only get one, I strongly recommend bow thruster.

 

[Seevee]

Here's a thought.....


With twins, it's especially hard to move the stern sideways, but fairly easy to move the bow. So there could be an argument for a stern thruster.


Especially if you're adding one, because the stern thruster is significantly cheaper and much easier to install.

The BIG advantage of a stern thruster is backing into a slip, where it's easy to tweat the stern between the pilings and motor back.

 

[Comodave]

I absolutely love my stern thruster. Eventually I will add a bow thruster but for now the stern is way better than nothing.

 

[DrissZougari]

I personally think that adding thrusters to a twin screws boat is just plain waist of money however, a bow thruster should help on some long tunnel drives boats such as the 50ft plus Sea Rays. on my single screws, I always preferred bow thrusters because i can back into any slip steering with the thruster instead on the wheel. yes, Stern thruster (electric thrusters) are much cheaper to install and can be DIY in few hours.

 

[Nomad Willy]

MYTraveler,
What if you were backing down on an anchor in a head on breeze.
And if your backing prop walk helped what little it could the breeze will push your bow to starboard. And of course if you give her left rudder and a blast of throttle you may bring her head up but you won’t be going backwards anymore.

But a thruster (either end) may keep your boat lined up straight.

 

[Baker]

My response is a little different -- I believe that with a bow thruster on a twin screw boat, a stern thruster is not necessary to move the boat straight sideways or in any other direction. I don't have a stern thruster and wouldn't use it if I did.

I have both....and I will say again......a stern thruster is a lot more advantageous than you would expect!!!

 

[Comodave]

We have twin engines and at some point I will add a bow thruster, we currently have a stern thruster. I will add the bow thruster because as we get older it will enable us to keep boating longer and that is something I can’t put a valve on, certainly way more valuable than the cost of the thruster.

 

[Snapdragon III]

The new boat I just bought has twins, but a single rudder in the middle, so doesn't get prop wash at low speeds. It also has a hydraulic stern thruster. The one time I got to try docking it, the hydraulic pressures were adjusted wrong and the the thruster had maybe 1 HP. I had a very hard time getting it to do what I wanted it to. It also has a huge full keel, which I am not used to. I am sure I will figure it out eventually, but it was pretty stressful with a new boat. After that trip to the fuel dock, we adjusted the hydraulic pressure and the stern thruster is working much better, although I suspect it is still not developing anywhere near the 15hp it is supposedly capable of. I suspect the pressures were turned down because the triple V-belts that drive the hydraulic pumps couldn't transfer enough power at idle speed, and would slip like crazy if you fully turned up the hydraulic pressure. I am going to investigate further when I get the boat back to Washington.

 

[CaptainSEA]

I’ve got both hydraulic bow and stern thruster on a twin engines. I enjoy to have both, not mandatory but extremely comfortable when wind and current are combined.
Having a twin I make more use of my bow thruster to get to my berth. It is worth mentioning that the efficiency of the thrusters is decreased with boat speed. Also by experience very often the thrusters are under dimensioned in terms of power whereas we need them when the berthing conditions ( wind and current) are difficult...

 

[Bacchus]

Beaverlake
After about 11 months and 160+ thoughtful responses I think you have reached THE correct answer...
"It depends"
I agree. As others expressed their preferences (clearly and without any animosity noted) it became clearer to me that each have some very valid basis for their preference and there are many variables involved in different situations.
Take even docking... where that was mentioned only a few specified bow or stern in, then you have prevailing wind & current, etc.
I am single with thrusters both ends and absolutely love them for a lot of reasons. Bottom line it makes life easy and we dock more often with a smile than frown and believe our arrangement and boat will let us boat 10 +/- yrs longer than we could have with our previous boat w twins but no thrusters.
I also installed a wireless remote a year + ago and it does come in handy in a few situations we run into often. Again which end depends on the situation.
I do find either will / can produce similar motion... one with a little more efficiency and I usually alternate pulses bow & stern especially when wind & current are stronger. It's nice to never have to worry about overloading / heating.

 

[Seevee]

Bakers comment "a stern thruster is a lot more advantageous than you would expect!!!"


Absolutely true..... especially if one is a single. But even with twins it will move the stern sideways when no other thing will do that.



With twins, using differential thrust moves the bow, not the stern. And, yes, you can still get the job done with that.


I've got bow and stern thrusters on my single. When backing in, with no wind or very little wind, my Admiral at the helm and me with the remote can put the stern within an inch or two of where we want to be. Super handy!


I'd often come home after a long evening at the Legion, coming thru my canal at night.... my neighbors dogs would be barking for a bisket. So, I'd cock the boat sideways, back in a bit to their dock, walk back to the stern with remote and bisket in hand and bump the stern within inch or two of their dock to give the dogs their treat. Loved it. (even though I hate dogs).

 

[Simi 60]

No thrusters and single fan on ours.
I can control where the front goes but have almost zero control over the bum, she gradually wants to walk to port even with helm hard over.

Stern thruster would be most advantageous to us, every time we have got out of shape I reckon it would have been easily fixed with a stern thruster and, a far easier and cost effective install.

Probably have to be hydraulic, not sure if electric would be up for it.

Have even toyed with the idea (over a few drinks) mounting sideways a Yamaha 9.9 electric start 4 stroke high thrust outboard with remote linkages, all of which I have sitting back at the dirt house.

It "may", if rotated fore and aft even have enough punch to move us if we had a mechanical breakdown, have seem them on heavy work barges before.

 

[markpierce]

Haven't yet met a twin-engined boater that needed a thruster.

 

[BruceK]

Bakers comment "a stern thruster is a lot more advantageous than you would expect!!!"

Absolutely true..... especially if one is a single. But even with twins it will move the stern sideways when no other thing will do that.

With twins, using differential thrust moves the bow, not the stern. And, yes, you can still get the job done with that.

.

Doesn`t the bow move because the boat rotates on its axis due to the stern moving? One end moves, and that moves the other end.

 

[Portage_Bay]

Every boat is different and behaves differently. The pivot point due to rudders is generally 1/3 of the waterline length aft of the bow. The pivot point from opposing the engines is much closer to the propellers.

Doesn`t the bow move because the boat rotates on its axis due to the stern moving? One end moves, and that moves the other end.

 

[rslifkin]

It depends on the boat. On mine, for example, it's easy to move the stern sideways, but takes more space and time to move the bow. The pivot point from engine thrust is fairly far forward, so when you spin, the stern moves about twice as far as the bow.

Other boats will be different. In my case (twins), I'd have use for a bow thruster at times, but a stern thruster would be a complete waste.

 

[Beaverlake]

Yes Don (bacchus) it has been interesting. I guess I could have answered my own question before posting (“it all depends”) but I guess I was (over)thinking economics - as in bang for the bucks. Retrofitting a conventional bow thruster is pretty spendy, less so for a stern thruster. No tubes, easier access, theoretically shorter wire runs, etc. And based on the comments a stern thruster dose seem to deliver help when needed - single or twin, full keel or not, etc.

That noted, for us at this point, if by February the border looks to be open by June next year then we’re off for a loooong cruise north from Anacortes including a fishing run for me out to Barkley Sound. If it looks like a lengthy closure, however, then Knot Home will likely become someone’s next boat in 2021.

Back on topic - I was going to do a follow up post anyway since this morning I got to thinking about our Tolly 44 that had both bow and stern thrusters and how much I appreciated the extra help *when I needed it*. It wasn’t often, but on those occasions the maneuvers became a joy and not an existential threat to our hull finish.

Thanks everyone - a lot of great input and observations!

 

[Baker]

Haven't yet met a twin-engined boater that needed a thruster.

There needs and there are wants. But my previous boat was a twin with no thrusters. I would not have ever added thrusters.....I certainly never felt the need. But current boat is twins with both thrusters. I generally use the thrusters to "fine tune" my maneuvers. I never rely on them to get me out of trouble....because they likely won't do that. They are simply a convenience.

 

[kthoennes]

Boy, this discussion and debate really surprises me. I have twins, no thrusters, and a million square feet of windage, very high profile. I can make the butt do whatever I want, but the bow has a mind of its own.

 

[rslifkin]

Boy, this discussion and debate really surprises me. I have twins, no thrusters, and a million square feet of windage, very high profile. I can make the butt do whatever I want, but the bow has a mind of its own.

Sounds like my boat.

 

[aevdg]

My husband and I have been boating for about 35 years. He is a licensed 100 ton captain. We have taken our boats from Alaska to the Gulf of Mexico.
I get a bit irritated with people who say that bow/stern thrusters aren't necessary - that more practice is needed---when the absolute correct answer is 'IT DEPENDS'. When we were berthed in SF bay, we had a slip in Marina where all the wind was blocked. My husband could dock the boat alone and step off alone to tie off. It was a double finger slip and when the big fenders were down the boat was snug in the slip with little movement. We had a Grand Banks - and no bow and stern thrusters were necessary.

Now its 35 years later. We have a KK42 - heavier with a lot more windage. Both boats by the way, single screw. We are on a side tie with the boat in front of us about 4 feet away. We are near a bridge which leads to the harbor and when the tide changes - there is a major current. We also have Santa Ana winds which can be easily 40-50 miles an hour - coming from the east. I have had two back surgeries and my knees aren't what they once were. Having bow and stern thrusters (and headsets btw) gives us the ability to put that boat on the slip six inches off the dock, where I can step off and get the spring line on the cleat. It becomes a non event.

So-----if you want bow/stern thrusters, in specific situations, they make life a LOT easier and docking much more pleasant. Make your own decision.

 

[rgano]

Sounds like my boat.

Like every boat and ship with twins I ever conned.

While working in the oilfield on a 189-foot offshore support vessel, I was taught a neat trick. To parallel park between two other ships in a space just big enough for us we pulled up alongside the ship ahead - our berth was on the starboard side of our ship. The 8V71 diesel which powered the bow thruster was started ahead of time, and the thruster used to kick the bow out about 30-40 degrees while the stbd engine was backed slowly to move the ship toward the berth in a movement just like you perform parallel parking a car. Once sternway was established, the stbd engine was stopped. As our bow cleared the ship ahead, the bow thruster used to push our bow toward the quay to our stbd, and the port engine was clutched ahead slow as we settled parallel to our berth and just three feet out.

I have learned to do pretty much the same with my single screw and thruster.