Bow Thruster Performance

Hi everybody, I have a Mainship Pilot 30. The bow thruster gives me about 3-4 max thrusts and then runs out of steam and turns at a little whir at lower RPM. My mechanic says it's normal and only designed for short bursts and not designed to spin boat around on its axis. I understand that, but just wondering others experience.

Not sure what you mean by 3-4 max thrust, but length of time of your bow thruster is determined by temperature and battery. Some bow thrusters heat up quickly, others not so much. And if your battery is whimpy, then your bow thruster whimps out quickly.

Is it a 12V or a 24V system - more is better?? Do you have big enough batteries in decent condition?? Our 24V thruster used 2x4D's. Once when batteries got weak it did as yours. Electric bow and stern thruster draw a very high current and deplete a weak battery quickly.

I have a stern thruster that is the same as a bow thruster except for the different tunnel. Mine is rated to run for 3 minutes before it overheats and has a thermal cutout. I don’t run it that long because I have never needed it for that long at once. But how long does yours run? If it is only 3 or 4 short bursts then there is a problem. Give us a better definition of the 3 or 4 bursts.

Skyboss
Is this a change from prior or been that way?
Always Worth checking cleanliness & tightness on all connections as well as battery condition.
From there I'd be checking voltage at the thruster while it is being activated.
I'm guessing yours is likely a Sidepower similar to mine on my '08 34HT.
I pulse them for 5-10secs at a time. Once you start the side motion it will continue to coast long after you disengage the thruster... pulse again as needed.

Couple questions ?

When you say "only works for 3 or 4 max thrusts" -- how long is each of those thrusts your talking about ?
How much rest time between thrusts ?

What brand Bow Thruster do you have ?

Plastic props or stainless steel props ?

I am presuming it is electric -- is that correct ? Some are Hydraulic.

If it is an Electric Thruster, (as I am presuming) -- how many volts is it supposed to operate with ? - most likely - 12-V - or 24-V- or (could possible be 36-V - or 48-Volt - but I doubt it for 30 footer) ?

How many HP is it rated at ?

What diameter is your tunnel it is mounted in ?
Or is it the bolt on bow external type ?

What is the diameter of the prop in that tunnel ? -- I want to see how snug a fit the prop is to the tunnel - clearance from prop tips to tunnel wall is critical Tighter the fit the better, for top performance.

Does it have a single prop or dual prop design ?

Exactly what battery & size & how many do you have on the boat to operate the thruster ?

How old is that battery ?
Is it a starting battery or a deep cycle style battery or is it an AGM ?

When was it last tested with something like a quality state if the art Midtronics capacitance style battery tester ?
if so, when & what did it say about the battery ?

Is that battery a dedicated Thruster only battery or maybe Thruster & Windless only battery ?
Or is it shared - like the house battery, or engine starting battery, or - ??? - as well as thruster battery ?

How is that battery for your thruster recharged when at the dock on shore power ?
Is it a 4 stage charger that equalizes the battery on regular schedule ?
How is it recharged when under way ?
If charged by the alternator, - key item is - What kind of regular ? BALMAR or is it the stock internal regulator in the alternator ?

What CCA is the battery or batteries that you have running your bow Thruster ?

Are your batteries wired in series or parallel ? -- or is it just 1 battery ?
Example: - like two 6 volt golf cart batteries wired in series to get 12 volts, or are the batteries wired in parallel like two 12 volt group 24 , 27, or 31 batteries hooked positive to positive & negative to negative as they are wired in Parallel ? Or do you have a single or dual Heavy Duty dedicated "8D-HD-T" batteries running the thruster ?

Are the battery terminals post style or are they terminal stud style battery connection points ?

If post style - what kind of adapters are you using to hook to the cables ?

Are your batteries a flooded lead acid type battery or an AGM type battery ?

What size coper cables do you have running from battery to the thruster motor ? Are the ends crimped or soldered ?

How long is the run from your battery to the thruster motor for each cable ?

How old is the system on your boat ?

What maintenance have you done to the system over the last 2 years, if any ?
-----------------------------------------------------------------------------------
I am a long time thruster advocate & had them on a dozen different boats over the years. Different brands & different styles & different sizes.

I currently have both a bow & stern thruster on my Kadey Krogen 42 & they work great.
they are -- WESMAR Dual Prop Bow Thruster-- that is 24-Volt & powered by dedicated battery pack of 4 group 31 AGM batteries - Series / Parallel wired -- for 24-volt.
----- 10 HP at bow & 13.5 HP at stern. Love my Thrusters !

I can spin my boat 360 degrees with no issues.

These questions & your answers, will supply the needed info To help diagnose your issues & will help the team here at TF to assist you with your dilemma.

BTW - a picture is worth a 1000 words.

Thanks.

Alfa Mike

I have a pair of Wesmar 18hp units and I can do the same (spin the boat in still water), but there have been a couple of times that the wind and current are just too much. I use them mostly as a booster to differential thrust when docking and maneuvering in tight places. They are also helpful to aid in adjusting bow and stern lines when there are adverse currents or wind.
They are a useful tool, just like twin screws or skill using spring lines. They all help.

Thruster Power

There are two considerations relevant to thruster performance -- max run time before thermal overload, as others have commented upon, and max wind speed at which thruster can effectively move the boat into the wind. Mine is rated at 5 minutes and 25 knots, respectively. I have only tripped the thermal protection once, when docking (end tie) with the wind directly off the dock. I don't remember how strong the wind was, but it was enough to make docking (end tie) difficult, and I did make excessive use of the thruster while my crew got off the boat. Since then, in heavy wind, I more specifically discuss procedures before getting to the dock.

I have never "maxed" mine out. I usually run 2 - 3 second bursts. Generally about 2 is all I need to nudge the bow into the dock. I did shear the pin once, it is a sacrificial part. Don't really know why it sheared but the fix was pretty easy. Now I have a couple on hand, I had to order the first one.

pete

The "maxed out" power loss is probably bubbled on the batt plates, not a dead batt.


Start batts have more plate surface area than deep cycles so can do bursts of power better.

rsn48 said:

Not sure what you mean by 3-4 max thrust, but length of time of your bow thruster is determined by temperature and battery. Some bow thrusters heat up quickly, others not so much. And if your battery is whimpy, then your bow thruster whimps out quickly.

Click to expand...

I mean 3-4 bursts of considerable thrust with lever in full deflection followed by noticeable decrease with lever in same position. Thanks

Skyboss said:

I mean 3-4 bursts of considerable thrust with lever in full deflection followed by noticeable decrease with lever in same position. Thanks

Click to expand...

Boss
Robbing from Alfa Mike's long post, please answer:
- how many seconds is each burst?
- what is battery voltage before and after bursts, as measured by a VOM meter on battery posts?
- dedicated thruster battery?
- age and type of battery (s)?

And how near (or not) the thruster to the battery/ies?

-Chris

1. two to three seconds
2. never measured that
3. yes
4. new /unknown*
*unable to answer as not near boat now

ranger42c said:

And how near (or not) the thruster to the battery/ies?

-Chris

Click to expand...

Battery is right next to thruster

You should definitely be able to spin the boat (if needed). My boat is considerably heavier than yours and I can use the bow thruster MUCH more than the way you're describing.

My guess would be a weak battery or the battery isn't big enough. Check the manufacturers specs and see what group they recommend for your thruster. Group 24, 27,31 etc.

Also check the water level in the battery (if it's that type). If its low, then fill it up with distilled water (not tap water).

Skyboss said:

I mean 3-4 bursts of considerable thrust with lever in full deflection followed by noticeable decrease with lever in same position.

Click to expand...

It sure sounds like a low battery!

Try this: My 24v thruster was acting the same way when I bought the boat and I fixed it with these.

Codger2 said:

It sure sounds like a low battery!

Try this: My 24v thruster was acting the same way when I bought the boat and I fixed it with these.

Click to expand...

Geez Walt, those should push your boat sideways at 8 knots!

I agree that most likely cause is weak batteries. I just checked a few Vetus specs and Vetus bow thrusters are spec'd at 200 amp draw for both 12V and 24V systems with typical 4 minute continuous run times. So, a 24V thruster theoretically puts out 2x the thrust of a 12V system consuming 4.8 KW vs 2.4 KW. It is not about how many AmpHrs you theoretically have but rather whether the batteries, cabling and connectors and are in good enough condition to deliver at the required peak current flow.

Chrisjs said:

So, a 24V thruster theoretically puts out 2x the thrust of a 12V system ...

Click to expand...

??

I'd have thought a thruster rated at (e.g.,) 100 lbs of thrust (or whatever) would but out 100-lbs of thrust no matter what the voltage.

??

-Chris

sunchaser said:

Geez Walt, those should push your boat sideways at 8 knots!

Click to expand...

I can't attest to the speed but I can say that when I move the thruster handle in the slip, the boat almost jumps with the thruster movement! I have a SidePower 10hp 24v thruster.

"I'd have thought a thruster rated at (e.g.,) 100 lbs of thrust (or whatever) would but out 100-lbs of thrust no matter what the voltage."

Sorry, Chris, you are correct.

For 2 matched thrusters, the 24V unit has 2x the volts and 1/2x the amps, equals same power as 12V at 2x the amps. So for example, matched Vetus units 6012D/6024D) both are 4HP, 60KgF , but one is rated at 280A, the other 140A.

Same point though about the weak point being battery condition, cable etc given the high current draw, especially with 12V unit.

I had a Side Power thruster on my 30' Pilot and would bump it for a maximum of 10 seconds, never trip the thermo switch in 5 years of ownership, can't remember the specs but I had an 8" tunnel.

My same year and model boat as the PO's came to me with a Side Power SP-55 powered by two parallel AGM starter batteries, the only batteries in the boat at the time. Those two batteries, which are in the forward part of the engine compartment, are at least six years old and still powering the SP-55 with no problem at all. I typically use it in several 5-10 second bursts, and I can run it for longer shots if I feel the need with no ill effects. I'd be looking at the battery condition, the condition of the connections, and possibly renewing the thruster's motor brushes.

When the batteries deteriorated on my Sidepower rear thruster I probably didn’t recognize it as soon as I should have. It caused the contractor to act erratic and not pull in every time. Also just gave short bursts. Put a voltage meter across the batteries and energize See what the specs call for. The Sidepower tech support was very helpful

Sidepower advantage

Four factors, 24V, battery amp hours, thruster size, and proportional power option all contribute to minimizing overheating and maximising duration. Doing a proper windage calc starts the selection process. This puts a size or two larger thruster than generally needed day to day, and then with proportional thrust drawing only only the current to get the job done, run time is huge. I spin my 44' MT with continuous thrust in full circles, no loss of power.