Bow Thruster vs Stern Thruster

I guess I should add that I didn't really need a bow thruster as I can turn in my own hull length by judicious use of throttle and rudder, but I wanted a bow thruster (as a toy), and at that price I couldn't refuse, even if it was oversized.

But as my boat has a fair amount of windage, and it can get breezy in my harbour, I am sure glad I have it. It is a great tool and I use it all the time. Came in one time after the breeze picked up this summer and it can easily counter a 25 knot breeze on the beam.

Maybe the novelty will wear off, but I doubt it.

Marin said:

Hmmm.... the electric thrusters I hear being used sound like rocks in a giant cuisinart. Absolutely horrible sounding things and you can hear them all over the marina. In fact I think their noise is part of the stigma that seems to be attached to using a bow thruster. It's like shouting to the world, "Look at me, I don't know how to maneuver a boat properly!"

I think a thruster is geat tool if you have one. The single-engine GB36 we chartered had one and it came in very handy on a number of occasions, particularly as we were new to this kind of boat and boating. So other than the people who use them to steer their boats as a matter of course (like a car) even in open water, I don't belittle having or using a thruster.

But I would have thought that the manufacturers of electric bow thrusters would have by now figured out a way to make them quiet other than the sound of the water being moved. I have no idea why they are so irritatingly noisy--- it's just an electric motor so I assume the grinding sound is the gearbox. The few hydraulic ones I've heard don't seem to make any mechanical sound at all.

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I know exactly what you mean. But mine are extremely quiet. Both bow and stern. Most of the louder units in our marina are hydraulic not electric.

Marin said:

Hmmm.... the electric thrusters I hear being used sound like rocks in a giant cuisinart. Absolutely horrible sounding things and you can hear them all over the marina. ...

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Good. Mine sounds the same. So it must be working OK even if it sounds broken.

Curt R said:

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Thanks for your responses. I have always been concerned that the helm won't respond to rear port. I will try more power. I wonder now if the rudder and prop are correctly proportionate. Attached is a pic took last week when the boat was hauled.

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What I know about hull design and the proper sizing of props and rudders wouldn't cover the head of a pin, but from your photo that looks like an awfully small rudder to me.

Rudder position makes little or no difference on my boat when backing because the prop wash doesn't hit the rudder, only the minimal flow of water from backing.

My marina has a very narrow fairway and there's often current and wind so docking stern to would be verry difficult without a bow thruster.

There is a choice of a bow thruster and stern produced in the Netherlands as a combi system. HMP.nl

Curt R said:

View attachment 14399

Thanks for your responses. I have always been concerned that the helm won't respond to rear port. I will try more power. I wonder now if the rudder and prop are correctly proportionate. Attached is a pic took last week when the boat was hauled.

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I just re-read your post and I screwed up. I had missed the rear port. Going backwards your rudder may be ineffective at best. Propwalk will be a dominant force that the rudder may not be able to overcome, particularly at low speeds. So more power is not necessarily the correct solution.

For that, in a single engine boat, the more effective technique is to " back and fill". You get the boat going backwards and then correct the sideways yaw of the stern by putting the rudder over, giving a shot of forward thrust against the rudder to straighten the stern out, then immediately back into reverse (or sometimes just neutral if the boat is still moving backwards) to continue backing, another correction, and so on. It's all about inertia and if done correctly your boat will track backwards in a straight line as you correct for prop walk along the way.

Much easier to do than explain.. I learned to do this with 60' narrowboats in England which back horribly but have big rudders and fairly powerful engines. Once you get the hang of the timing and using inertia to your advantage it's an easy thing to do and is actually kind of fun.

On thrusters for my boat I'd opt for a stern thruster.

One other big reason is that they are so easy to install.

Almost the only time I feel the need for a thruster is when backing down on an anchor, especially in a breeze. One could compensate for prop walk w a bow thruster but the boat would be going sideways. I'd rather be going straight back.

And I can position the bow practically anywhere the stern thruster would only increase that capability.

But of course thrusters at both ends is no doubt ideal but any thruster will funnel significant funds away that could otherwise be used for much more useful things than thrusters.

I noticed Mark didn't say "don't need no stink'in thruster".

First, bow thrusters, tunnel or is it produced by Holland Marine Parts are used primarily to assist in maneuvers such as the mooring in ports, their power is individually tailored to the size of the unit and is calculated to overcome the force of the crosswind 5-6 bft. Tests of these systems in the company so I can accurately determine if their power is correct or not. Tunnel are efficient but noisy and not very flexible in installation, Dutch very quiet, small holes on the sides of the nozzles can be mounted on the bow or stern, but limited power to 90kgf. Best to see how they work and compare the two you can always find a compromise. Ryszard

Curt R said:

View attachment 14399

Thanks for your responses. I have always been concerned that the helm won't respond to rear port. I will try more power. I wonder now if the rudder and prop are correctly proportionate. Attached is a pic took last week when the boat was hauled.

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That looks like the image of an mmc with dual engines not a single. The ones i have seen with a single have much bigger rudders.

bfloyd4445 said:

That looks like the image of an mmc with dual engines not a single. The ones i have seen with a single have much bigger rudders.

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The rudder and prop look to me like they are on the centerline of the boat judging by their relationship to the centerline vee in the transom.

I'm impressed how fast the small propeller of the bow thruster spins the 14-ton Coot.

No Thruster. Single Screw. Pulls starboard in reverse. I speak kindly to the wind, whisper to the current, and most importantly, my marina neighbors are outrageously helpful. A few strategically placed fenders help too.

IF a compressor doesn't even go a year , there is probably a reason it was killed , not just a Mfg failure.

Low voltage , high head pressure , lack of cooling , no timer for low power restart, many many ways to kill a compressor.

You need a competiant repair guy.

Ben said:

A few strategically placed fenders help too.

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Docking by braille. I can relate to that.

We have both bow and stern thrusters on our 47ft single screw Selene. The stern thruster is marginal when used alone. It is helps when spinning the boat using both thrusters and helps push the stern in to the dock when tightening attached stern lines. Having to choose between both, I would certainly go for the bow thruster. I think I have even seen bow thrusters than can be attached externally without the need to cut a tunnel, that might help keep costs down.
I continue to envy sailboats that can spin on a dime without any thrusters. Yes, I can turn my boat, but it sure does not handle like my friend's same length sailboat, despite having a decent size keel.

Whatever thruster one chooses, make sure that it is not underpowered for the size of the boat. My stern thruster allows me to run my boat parallel to my dock, then by hitting the joystick it turns my boat perpendicular to move it into the slip. Of course, my thruster is rated for a 40+ foot boat and moves my 32' vessel with ease.

sunchaser said:

Ron said:
"Why would you need an inverter to install a bow thruster?"

Boat is 12V and thruster motor is 24V

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It seems like that would be pretty inefficient at high power. And pretty expensive. Would two 12 volt batteries in series have been an option?

Ben said:

No Thruster. Single Screw. Pulls starboard in reverse. I speak kindly to the wind, whisper to the current, and most importantly, my marina neighbors are outrageously helpful. A few strategically placed fenders help too.

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Welcome back, Ben!

I must admit, your handling skill in the close quarters of our marina has impressed me more than once.

Ben said:

No Thruster. Single Screw. Pulls starboard in reverse. I speak kindly to the wind, whisper to the current, and most importantly, my marina neighbors are outrageously helpful. A few strategically placed fenders help too.

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Ben's been readin' ma mail.....
We manage...but if I was able to buy a newer, bigger boat, I suspect I would go with bow thruster...

Belle has a deep keel, high windage, and twin screws. If the winds not messing with you the current is. She is not as nimble as my previous boats and you need to be ready to pour on the power in tight quarters if you want her to behave. We will be adding a Sidepower to her bow before spring and the quote I have is for $14,000 complete. Two 12 volt batteries wired for 24 volt with 10-inch tunnel unit for 50-60 footers. We have learned to use spring lines getting off a dock, and the stern is controllable. I love when somebody wants to criticize adding a thruster - like we just can't drive good enough. They are either blow boaters - whose keel design does not begin to match a trawler keel, or they are jealous because they either can't or choose not to pay for this luxury item.

BelleAurore said:

I love when somebody wants to criticize adding a thruster - like we just can't drive good enough. They are either blow boaters - whose keel design does not begin to match a trawler keel, or they are jealous because they either can't or choose not to pay for this luxury item.

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Yes and they drive a standard shift, no A/C, no Power Steering or Power Brakes and an AM radio if they even have one. Right!

I'm not opposed to practicing without them once and a while but if they are available, not to using them or seeing the value in them is a bit old fashioned or hard headed. Not that anyone here is either or God forbid both.

I've seen the Chesapeake waterman's docking contests on the Internet and these guys can dock a single screw workboat without a thruster in short order, but most of them have been docking the same boat six days a week for 30 years or more. And it's a workboat and they're docking between two wooden pilings, not between two million dollar yachts.

For the rest of us, any tool that makes it easier or safer is a good thing. I take my boat out (and bring it back) to enjoy myself, not to impress bystanders or virtual people.

rwidman said:

I
....any tool that makes it easier or safer is a good thing. I take my boat out (and bring it back) to enjoy myself, not to impress bystanders or virtual people.

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I think that sums it up as well as anything. Can one run a boat, single or twin, without thrusters? Absolutely. Can a thruster, bow or stern, make handling a boat easier which can also translate into safer? Absolutely. If you have one, or want to spend the money to install one, is it admitting you are a less competent boater than people without them? Absolutely not.

There have been plenty of times with our twin engine boat that I've wished it had a bow thruster. We have so far always managed to deal with the situations that have come up, but there is no question that if the boat had a bow thruster it would have been easier or faster to deal with some of them.

BelleAurore said:

Belle has a deep keel, high windage, and twin screws. If the winds not messing with you the current is. She is not as nimble as my previous boats and you need to be ready to pour on the power in tight quarters if you want her to behave. We will be adding a Sidepower to her bow before spring and the quote I have is for $14,000 complete. Two 12 volt batteries wired for 24 volt with 10-inch tunnel unit for 50-60 footers. We have learned to use spring lines getting off a dock, and the stern is controllable. I love when somebody wants to criticize adding a thruster - like we just can't drive good enough. They are either blow boaters - whose keel design does not begin to match a trawler keel, or they are jealous because they either can't or choose not to pay for this luxury item.

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none of the above. The hull truth is that they are just jealous and envy you cause you have the money to spend and they don't. Don't you remember the kidfs in school when you had a candy bar and they didn't?

We have a 24 V Bow thruster, 2 8Ds in series and a 24 v charger that requires AC from Genset or shore. I have not run out of 24V before I got the maneuver complete. . It is a Wesmar 15 hp in a 10 inch tube. !2 would have been better but would not fit.

Be sure the tube sits low and as far forward as possible to give you best leverage. Having a Bow thruster when moving backwards is like having a rudder on both ends of the boat. If the real rudder doesn't work (an emergency IMHO) the thruster can do some steering while you figure out the problem.

xfedex said:

We have a 24 V Bow thruster, 2 8Ds in series and a 24 v charger that requires AC from Genset or shore. I have not run out of 24V before I got the maneuver complete. . It is a Wesmar 15 hp in a 10 inch tube. !2 would have been better but would not fit.

Be sure the tube sits low and as far forward as possible to give you best leverage. Having a Bow thruster when moving backwards is like having a rudder on both ends of the boat. If the real rudder doesn't work (an emergency IMHO) the thruster can do some steering while you figure out the problem.

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ah, never thought of it for steerring. thanks

We're contemplating one of these:

Yacht Thruster - Bow and Stern Thrusters Applications


Seems perfect for a DIY project, and I like the idea of a small hole in the boat vs the traditional tube. The company touts the exposed motor has extended run time due to the cooling action of the surrounding water.

Last time I checked pricing it was in the neighborhood of 5K (including haulout for the unit install). The haulout can be a haul and hang vs blocked.

Opinions?

I have a single screw and occasionally have opertunity to run a twin.
I learned that to end confusion as to what and how the boat turns.
Is to put both hands on the shifters and point your thumbs towards each other.
which ever way your thumbs are pointing that is the way the boat will turn.

Right tumb pointing left and forward the bow turns left.
Right thumb pointing left and in reverse the stern backs left.
left thumb pointing right and forward the bow turns right.
Left thumb pointing right and in reverse the stern turns right.
all you have to do is look at your thumbs.

Never let you dog do this.

No thumbs.

SD

It kind of begs the question of which appendage does the pointing for a single screw???