Bow Thruster Cables

Mat-C is there any way to shorten the cable run by rerouting them? When I looked at the Lewmar installation information they indicated 1/0 was good for a 50' run. You wouldn't need to find much to get there...

 

The thruster (and windlass) run off the house battery bank. There is a separate battery for the engine. Though having said that, I would usually only operate the windlass (and thus thruster) with the switch to 'both' so that the engine is covering at least some of the discharge.

Bglad - no I can't shorten things up - at least not with the existing set-up...

 

"I have fixed many corrode/undersized cables."

...I'll second that, and also had to do a febuild under the fwd berth when it all caught fire on one boat too.......

...if the boat is so small that a battery is a problem, why have a thruster anyhow....

 

That is an excellent question.

If you really need a thruster, then you had best install it properly.

If it's not worth the money to do the job right then perhaps you don't really need it.

-Tom

 

Adding a second smaller cable in parallel to an existing under-sized cable is a poor approach to solving this problem. If you opt to run a new conductor (two actually, + and -) then why not size them appropriately instead of band-aiding? The cost will be negligible when compared to raising the charred carcass from the bottom.
An alternative to installing an additional battery at the bow in the near vicinity of the thruster might be to add it somewhere along the way, the distance to the thruster thus being reduced to a length appropriate for the existing 1/0 cables.

 

"If you think safety is expensive, try having an accident (fire)."

 

Lets get real, when using a bow thruster you are not playing with 12V, most likely the engine will be operating so the voltage will start at 14.4V.

Do the voltage drop math with 14.4V as the start and see how much better the numbers come out.

FF

 

But when you overuse the thruster a couple of times and everything is not perfect, then your back to 12 volts or even below and the whole thing overheats and catches on fire....

Murphy is really a *****...

 

For the run times allowed by the manufacturer (they are rediculously low) are they really of benefit?

Put the dock on your leeward side if you're landing and the whole boat gets pushed in!

Back in and use your prop-walk to your advantage.

Nose in, tie a bow spring line and rotate around it onto the dock.

I'll ask one final time, is a thruster really necessary?

If so, then size and install it properly.

Murphy is a *****, and an opportunist!

-Tom

 

A thruster for most people is a crutch and a marketing ploy. On a small boat they are really not necessary, and honestly useless because if current or wind is so strong that you can't dock it won't help you either. Thruster make sense on much larger vessels like 45' and above and those should have what it takes to make it work properly.

Take classes on proper operation of a motorboat.

 

Agreed. Look at a cruise liner. Three of the biggest bow thrusters I've ever seen but no need for a tug boat assist anymore.

-Tom

 

Back to the point of the thread:
Relying on alternator power alone as the power source for a thruster isn't generally (in most applications) advisable. What would be the point of wiring through the house battery at all, then? Assuming the alternator is sized appropriately for this load (which very well may not be the case) what happens on that occasion when the thruster is used on batteries alone? Even worse, on batteries with a less than fresh charge? Contingencies need to be planned, and needing to use a thruster without the engine running is not far fetched. Even if it were, prudence requires that any reasonably likely scenario be planned for.

 

Ok - let me say from the outset, that if the larger cables are required, that's what I'd fit. I'm not into short-cuts or dodgy installations...

2nd - the batteries that I have installed are twice the required size as specified by the manufacturer. So, whilst I would generally only operate the thruster whilst the engine is running (just as I do with my windlass), if the need ever arose to do so, I could

3rd - I consider myself an experienced boat operator, with over 40 years operating all manner of boats. I can and do do all the things you suggest to get by without the thruster. However, the boat in question has quite high windage and very little draft. I would challenge just about anybody to dock it on a windy day without embarrasing consequences. Further, my marina berth doesn't allow me dock on the other side of the pier. On a number of occaisions, I've done the prudent thing and tied up elsewhere until the breeze has dropped out and come back later.
If a thruster is a viable option, then why not use one?

 

I'd like to back Mat-C up on this one. The notion that if you can't easily berth your boat without thrusters regardless of the situation, then you aren't a competent operator, is just plain nonsense. Otherwise those ships that were mentioned wouldn't need them either....
Yes a sterndrive allows you to vector thrust, giving greater control over the back end of proceedings. But it provides precious little help for the pointy end and if there is little in the way of lateral resistance then the boat can be quite a handful.

Back to the question at hand, and I'm with the others here: stick rigidly to the manufacturers instructions. Or at least get their approval in writing for any variations. The cost of arguing with your insurance company will far outweigh the cost of new cables....

 

..there are many boats that are "top heavy"...massive windage, and some then even have stern drives...an accident waiting to happen....yes, the bow thruster is well worth the effort under the circumstances.....again,, why not just use one of theose batteries and stick it under the berth with the motor.