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Bow thruster vs stern thruster

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    Bow thruster vs stern thruster

    Bow thrusters are great but expensive. And not a replacement for basic docking skills. That said, has anyone considered the effectiveness of a bow thruster (only) vs a stern thruster (only)? Bow thrusters are wicked expensive to retrofit but stern thrusters not so much. What difference in control should it make to move the extra pivot power from the bow to the stern? I’ve thought about this a lot calling up my high school and college physics classes and I’m not seeing the value in what might be twice the cost (to say nothing of losing some fresh water capacity in our 4788 with a bow thruster installation).

    Or maybe I’ll just continue improving my docking skills including line handling, fender placement, etc....

    Anyway - just noodling on the subject the night before Super Bowl.
    Patti & Gordon Lewandowski
    Sammamish WA
    1998 4788 (April 2018)
    ”Knot Home”

    IMO.... the props are at the stern so you’ve already got some stern thrust to some degree. In other words the stern has a better chance of being directed where you’d like it using engine power and steerage. The bow on the other hand being 47 feet further forward not so much.
    I’ll add there were many times a bow thruster would have made life a bit less stressful on dads 44 footer.
    Edmonds, WA
    "THE FIX"
    '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
    (.030 over-Vortec top end-part closed cooled)
    The rebuild of my 2556
    Misc. projects thread


      I am lucky in three ways, first my boat has both bow and stern, secondly a previous owner had larger rudders installed for better low speed maneuvering capability and third I have modified props that also aid in handling.
      That all being said, I try to use my thrusters as little as possible. I like being able to walk my boat sideways just using the prop wash and the rudders. But I have been in situations where current and wind were just against me in all ways. In this case I have used the mains and both bow and stern thrusters. Most of the time this will get it down. But there are those extreme times where only a spring line will get me in against the dock or off of it.
      If I were to have only one thruster, I would go with a bow thruster. Your stern already has two large thrusters (Mains). If you want to enhance them then change out the rudders or see if other props may be better than what you are running.
      I have seen many with bow thrusters think it will solve all their problems. They are not as powerful as one might think. I think this is do to undersizing them. Also so many are so very noisy for what they actually produce. Mine are Westmar and very quiet and work reasonably well. So if you are considering the expense of a thruster, first work through the operation, performance and sizing, then worry about cost. Either way will be expensive, but you want something to show for you money and you don't want to be reminded that you cut corners or didn't get what you wanted every time you hit that switch.
      I hope that this helps.
      Patrick and Patti
      4588 Pilothouse 1991
      12ft Endeavor RIB 2013
      M/V "Paloma"
      MMSI # 338142921


        When we were younger and a lot more agile, I would smirk at the boats that used thrusters to dock. As we got older I found that a bow thruster could make docking a little less stressful especially when the wind and/or current was pushing the boat away from the dock. Now that my wife and I are retired, and are far from agile I think anything that will prolong our ability to be on the water safely is worth consideration... This includes both bow and stern thrusters as it gives the ability to hold the boat against the dock so one of us can safely get off the boat to tie up


          I have found that helm time helps alleviate the need for thrusters.

          When we first get our boats we tend to get into situations that are beyond our boat handling ability and we look for answers to make docking easier.

          As time passes and we build skills we tend to stop looking for answers because we have developed enough skills to get our boats into and out of previously difficult situations.

          I’m not saying Thrusters would not be handy... Not at all. I’m just saying that we tend to forget why they seemed so important with a couple of seasons under our keels.

          4788 LISAS WAY - SEWARD ALASKA
          where are we right now​​​​​​???​


            When I bought my single engine trawler, I said to myself If professional fishermen and tugboat captains can learn to dock their boats without thrusters... so can I.
            I spent hours and hours practicing docking, even in a bit of wind and current and got to the point where I said. "I can do this!"
            Later that year I was assigned a slip in the Port Sidney marina where I had to go half way down a narrow fairway and turn 90 degrees into the slip.
            The wind was gusting riight on my beam when trying to get into the slip and it was blowing me into the boat beside me. I had one hell of a time that day.
            I installed a properly sized bow thruster that winter and from that time onward, docking was much easier and not a stressful ordeal.
            My current boat has bow and stern thrusters with handheld remote, I try to dock without using them but they are always on and ready to go and I never hesitate to use them if needed.
            I am never stressed now when docking because I believe that I have enough tools on hand to get the job done with damaging anything or my fragile ego.
            I often singlehand and use the thrusters to hold the boat against the dock when tieing up.
            I agree fully with PFW and Papa Charlies posts
            2001 Bayliner 4788
            Bow & Stern Thrusters
            330 Cummins
            Langley British Columbia


              As much as a I appreciate the comments and insight my original post was focused on the difference, if any, of using a bow thruster vs a stern thruster (not both). And again - my question was not meant to stimulate a discussion of thruster vs no thrusters. I am curious about whether or not a 2x cost for bow vs stern thrusters brings with it a significant additional benefit. Frankly at $20k or so I can’t afford a bow thruster but at half that I could consider a stern thruster.

              I can pivot our boat using the twin engines but try as I might (and I’ve tried/practiced often), walking sideways using twin screws and rudders on a 4788 is not that effective. For me. But for example, with a starboard-to docking I could theoretically approach the dock bow in, do the clockwise spin thing to twist the bow even closer to the dock, and use a stern thruster to counteract the twist thus bringing the stern in to the dock in parallel to the twist pushing the bow toward the dock. Theoretically.

              Of course if more/most transient marina docks in the PAC NW used cleats instead of the devil’s spawn bull rails I probably wouldn’t care as much because I’m pretty good at stepping out of the pilothouse and lassoing a dock cleat I can use to maneuver around a spring cleat, but then I can’t change that situation so there ya go.

              I hope a few more folks will chime in with experience using only or primarily a stern thruster or who are curious and have done some experiments. I’m wondering if we haven’t been “brainwashed” to spend more to put thrusters at the pointy end of our boats! ;-)
              Patti & Gordon Lewandowski
              Sammamish WA
              1998 4788 (April 2018)
              ”Knot Home”


              • ksanders
                ksanders commented
                Editing a comment
                I know it’s not on topic, but... If the concern is bullrails Grappling hooks are a very effective answer. I have two of them onboard and they make securing to a bull rail dock easy peasy.

              Hi Gordon, I keep hearing about bow thrusters being expensive. If you are handy, much of the work can be completed yourself. The only specialist aspect is boring the hole, glassing in the tube and fitting the propeller head in the tube while out of the water. Mine was done with a subsequent antifoul job, but the shop charged me under $2k for that aspect with 4 extra days on the hard ($500 for that). That’s the hard part. After that, it can be splashed and the balance completed at a more leisurely pace.

              Pulling apart the bed/drawer units isn’t hard and cutting out the rear fresh water tank for repair or replacement with new standard sized tank if you want to retain the additional water is cumbersome but doable too. The thruster units can be had for around $3k (Craftsman, Sidepower a little more expensive). By doing the grunt work yourself, a total budget of $6k is not unrealistic. Installing an AGM battery upfront close by, saves on the chunky cabling costs. So my 2 cents, think about that and see if you can find a shop that can glass in the tube. No doubt you’ll do the job better than most tradesmen anyway.

              Happy to provide a roadmap via Skype or FT if you want further info.

              John H
              Brisbane QLD Aust

              2000 - 4788/Cummins 370's


                Thanks John. A DIY is tempting but I’ve had my fill of non-core-𝐏𝐫𝐨𝐣𝐞𝐜𝐭 challenges working on our 4788. The boats have great spaces for people and stuff but not for service access. I’m pretty handy and the project isnt off putting, but all the crap one has to do and then undo for even simple projects is. A stern thruster, however, seems within reason relative to access even taking into consideration the placement of the generator.

                i think I’ll think about it some more, but I’ll probably spend the money on fuel and oil changes instead!
                Patti & Gordon Lewandowski
                Sammamish WA
                1998 4788 (April 2018)
                ”Knot Home”


                  I have had no thrusters, a bow thruster and now both bow and stern thrusters. That being said a bow thruster is a fantastic option to have. Having the boating experience I have I can definitely say nobody no matter how good they are can maneuver as precisely or safely as a boat equipped with it. A stern thruster on the other hand is a nice addition but as mentioned you already have rudders and props located in the back so less important. Almost impossible to get yourself into a situation if the boat is equipped with both systems, the maneuverability is just so precise and powerful if properly equipped.

                  The biggest issue is cross currents and cross winds which can really take over a vessel even with proper conventional input. There are times that the experience captain will choose another dock whereas the same captain equipped with the same experience and thruster would not need to.

                  Bottom line is thrusters are a valuable tool for use when conditions require them. Even during everyday docking one can bring a boat within a few inches and perfectly aligned to the dock so you can simply step off and tie up which I have done many a time.

                  Personally I would not add just a stern thruster.
                  Cheers, Hans
                  2007 Carver 41 CMY
                  Twin Volvo D6-370
                  Montreal, Canada
                  Midnight Sun I Photos


                    I travel solo at times and having a bow thruster is a great security blanket, specially when its an off dock wind with no help. With a bow thruster I can move my 4087 (with a lot of wind age) or any twin engine boat, sideways in either direction. At idle simply put one engine forward, one in reverse and push the thruster the opposite way to the forward engine-real easy and safe. Not sure that would work with a stern only thruster?
                    1996 4087 Lazy Days
                    2011 11’ West Marine Rib 350 Lazy Mac
                    2011 Porsche Cayman
                    2010 Lexus IS 250C
                    2008 Honda Ridgeline


                      Gordon- I’m a retired liveaboard in Tacoma. My ‘98 4788 has both bow and stern thrusters. Any time you want to come down and get some hands on experience docking the boat using only the stern thruster I’m more than happy to have an excuse to get away from the dock. Since our boats are sisterships it’ll tell you exactly what you want to know. Feel free to PM me if you’re interested.
                      Drew Haas
                      1998 4788 "Painkiller"


                      • Jim_Gandee
                        Jim_Gandee commented
                        Editing a comment
                        Wow, what an offer! Another example of why the BOC is such a great resource! Good on you Drew!

                      Only Stern thruster Will not help you.

                      and i think the 4788 has the watertank where you want to mont o bowthruster, so it has to be replast.
                      and to get it out you has to isamble the bed.



                        So, stern thruster only really has no benefit without the bow thruster. Like some people have mentioned before, the stern is easy to move along. The other reason why the stern is easier to manage is the overall mass vs. the side surface area. In side winds, the stern is heavier so the wind doesn't move it as much even though it has greater surface area. The bow on the other hand will definitely move, causing you to try and correct it. The stern only would force you to go WITH the wind in order to correct the boat while the bow thruster will allow you to go against the wind. In my opinion, stern only is useless at best and dangerous at worst. I'd rather go without any thrusters at all.

                        Now, $20K for a bow thruster is too much, I agree... but would you pay $5K for one? That's what I did with my boat and to be honest I couldn't be happier. I did the work myself and I learned a ton about my boat in the process.

                        I'll be doing a write-up of the install but it took me maybe 20 hours total time to install it by myself. If you have a helper the whole thing will go significantly faster.

                        I hope that helps.
                        Attached Files
                        Ships n Giggles
                        1993 Bayliner 4388
                        MMSI# 367412710
                        Day Island Yacht Club
                        Vice Commodore


                          Thanks guys! Drew,I might take you up on that offer. I love DIY projects but given the 4788 delightful access situation I don’t look forward to anything but the most basic and mostly cosmetic projects. I’m getting a little long in the tooth, wide in the middle, and rusty at the joints for anything more ambitious. Spending time with Drew I can replace theoretical physics with applied physics and perhaps close out this thread (and one on the Trawler Forum that now has about sixty posts that have drifted all over the place, often off topic from my original, and I think simple, question.
                          Patti & Gordon Lewandowski
                          Sammamish WA
                          1998 4788 (April 2018)
                          ”Knot Home”