Does a bow thruster make up for having only one engine?

skipjack27

Petty Officer 3rd Class
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Oct 6, 2009
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Where I live (Perth, Western Australia) river currents and local winds can making docking in pens difficult. In buying a new boat (motor cruiser in the range of 35-39'), I'm torn between two engines (twice as expensive to maintain, but much more maneuverable), and one engine (cheaper, but hard to get into a pen).

My question is this: would a bow thruster make up for the disadvantages of having only one engine in docking maneuvers?
 

Chris1956

Supreme Mariner
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Mar 25, 2004
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Normally a cruiser of that size would be powered by twin gas engines, as it is a bit heavy for a single big block motor to power. Are you expecting a single diesel to power it?

Certainly Bow Thrusters will help.
 

RotaryRacer

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This is hard to answer without knowing more about the boat that you have in mind.

A bow thruster seldom hurts, and can be a good aide to docking. However, it is my opinion that learning to handle the boat adequately with just the main engine is a good idea no matter what.

A boat that large with a single engine is typically going to be a displacement hull/trawler type of design. Typically these boats will have very large rudders that are very effective at slow speeds. Also, they will typically have large diameter props that aide slow speed control.
 

Captn B

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I agree with the above statements, it really depends on what type of boat this is. If its a boat that is desinged to get up on plane and run, you will need 2 engines. Twin engines are extremely manueverable.

However, if this is a full displacement haul with a single diesel engine a bow thruster would be very helpful. Even with the large rudders these vessels tend to have, a bow thruster will still help a lot.

Do you have any pictures of the vessel you are considering or the pen that you will need to keep it in?
 

smokeonthewater

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I would say yes mostly but there are things you can do with twins that you can't do with a bow thruster..... now bow AND stern thrusters with a single will do ANYTHING you want em to.
 

ssobol

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I would say yes mostly but there are things you can do with twins that you can't do with a bow thruster..... now bow AND stern thrusters with a single will do ANYTHING you want em to.

Except get you home if one engine fails.
 

HT32BSX115

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Dec 8, 2005
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In buying a new boat (motor cruiser in the range of 35-39'), I'm torn between two engines (twice as expensive to maintain, but much more maneuverable), and one engine (cheaper, but hard to get into a pen).

My question is this: would a bow thruster make up for the disadvantages of having only one engine in docking maneuvers?My question is this: would a bow thruster make up for the disadvantages of having only one engine in docking maneuvers?
Absolutely. But check the cost of a bow-thruster. They’re VERY expensive to buy & install........................ They are very convenient though.

But, if I was buying a NEW 39ft boat, I would still get it with twin engines.
 

25thmustang

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Mar 20, 2008
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I speak from no experience, but I imagine a hard current could overpower a bow thruster. I've been in some really strong currents/wind with twins that even a lot of power can't overcome and you need to rethink your approach.
 

haulnazz15

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I speak from no experience, but I imagine a hard current could overpower a bow thruster. I've been in some really strong currents/wind with twins that even a lot of power can't overcome and you need to rethink your approach.

Possibly, but I think it would take a REALLY strong current to offset a bow thruster. I wouldn't think of it in terms of "power", because although there's no comparison to the twin engines in HP, the leverage a bow thruster has being 20' further forward makes it much more effective for moving/holding the bow to a certain position. That being said, I'd rather have twins than a single w/ bow thruster.
 

Boydski

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Mar 21, 2008
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Possibly, but I think it would take a REALLY strong current to offset a bow thruster.

Lots of good comments above. A big 10 HP bow thruster has a lot of power and will make good headway against stiff winds and strong currents as long as you stay within the limitations of the thruster. Most electric thrusters can only be run continuously for a few minutes before they overheat (thermal breaker trips, which may not reset for 5-10 minutes). Hydraulic thrusters can run for as long as you can keep the fluid cooled, but are much more expensive to install.

A single screw, full displacement boat would benefit a great deal from a bow thruster. As mentioned above, they are generally slow boats with large rudders (aka Trawler). The bigger and heavier the boat, the easier it is to deal with wind and current as they have a much smaller effect on the boat's mass.

A twin engine boat is much more maneuverable than a single screw in close quarter docking. The single screw may require backing and filling (or the use of thrusters) to spin the boat around in tight spaces.

The benefit of the single screw boat is they are generally much more fuel efficient and you only have to maintain one main engine. I do have a small 40 HP wing engine (get home engine) in my boat and both bow and stern thrusters, which make docking pretty idiot proof....

YMMV,
 

dingbat

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Nov 20, 2001
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When to the annual waterman's festival last week. The docking contest is the highlight of the festivities. Boats ranged in size from 38 to 48 ft. In length. Most, single engine diesel inboards.

For whatever reason, didn't seem to have any problems putting the boats in a slip w/o a bow thruster......would lead one to think experience trumps "training wheels"...lol

http://www.youtube.com/watch?v=CLSbp8DOosQ Note the 11 year old competing
 
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achris

More fish than mountain goat
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May 19, 2004
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Hi skipjack,

I'm also a Perth guy. I know what you mean by currents and wind (something these guys don't have direct local knowledge of)....
Both twin engine and bow thrusters have there own advantages. With twin engines you have more control of the aft of the boat, and less over the bow (but still more than a single engine). With the bow thruster you have direct control over the bow and almost none over the stern (apart from the effect of the rudder, and will only have an effect when the boat is moving forward or back)...

Which way you go will be determined by exactly where you are and the conditions you have to deal with, but either way, learn to allow the prevailing conditions to help, rather than trying to fight them... I was asked to look after and use a 26' Randall for some friends (many years ago) penned at Fishing Boat Harbour. Berthing was a nightmare, as it only had a single 155hp diesel in it. It didn't take long to workout that trying to fight against the seabreeze was never going to win the war, so I changed the way I approached the pen, used the wind to my advantage... After that it was a breeze... ;)

HTH,

Chris.....
 
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skipjack27

Petty Officer 3rd Class
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Oct 6, 2009
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79
Many thanks for the very informative replies I've received. These have been very helpful.

A couple of respondents wanted to know more about the boat I have in mind - but unfortunately I can't be specific since I haven't actually settled on anything in particular at this stage. It's just that quite a lot of the boats I've been looking at are single engine, and that has me worried - given the problems associated with getting into pens in my local yacht club.

I appreciated the comments in relation to the desirability of getting to grips with handling single-engine craft. It's always been my understanding that such skill is the mark of a serious mariner! Sadly, my efforts to date suggest that it might be safer for all concerned at the yacht club if I have the assistance of more than one engine, or of bow/stern thrusters.

I'm also uncertain at this stage whether the boat I end up with will be a displacement, semi-displacement, or planing hull. All seem to be possibilities in the range of boat that I'm looking at. My preference is for a displacement hull craft; most of the interesting destinations in and around the Perth area are fairly easily reached at displacement hull speeds. But, who knows? If the right boat comes up, with a different hull style...

On balance, taking the current comments into account, my inclination at the moment is to look for a twin-engine craft (with or without thrusters).

Jeff
 

achris

More fish than mountain goat
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May 19, 2004
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When you get your boat and if you're interested in a run up to the Abrolhos, drop me a line....
 
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