Upgrade Bow Thruster - pitfalls?

[Sticky Fingers]

Hi folks,

The 20+ year old bow thruster on my boat (1999 Princess 460) is a 4HP / 3kW Side Power which is fed with 24v via long cables from the batteries in the lazarette. It's seriously weedy, can just about nudge the bow around provided there's no wind or current to deal with, but it's not really good enough. Thinking of improving it.

Plan is to replace the unit with a new Sleipner one (model TBC but it's a 185mm tunnel so probably the SE100 assuming it will fit in the space), and add a suitable 24V battery adjacent to it to eliminate the long cable runs. Use the existing cables as the charging circuit for the new battery. While I'm in there I might also rewire the windlass to consume its power from that battery.

Any obvious flaws in this plan? Any insight or better suggestions welcome.

 

[Tranona]

Will you be charging from the alternator or with a DC/DC charger? You don't need the heavy cables but guess it would be a nightmare to run new lighter ones.. Otherwise makes sense doubling the power of the thruster. Interestingly my thruster taken out of a new Princess after 1 week's use because of lack of power. Saved more than enough to cover the expensive Sidepower wireless remote. I also run the windlass off the same bow battery.

Bit of a wallet hitter for you but good future benefit.

 

[PaulRainbow]

Hi folks,

The 20+ year old bow thruster on my boat (1999 Princess 460) is a 4HP Side Power which is fed with 24v via long cables from the batteries in the lazarette. It's seriously weedy, can just about nudge the bow around provided there's no wind or current to deal with, but it's not really good enough. Thinking of improving it.

Plan is to replace the unit with a new Sleipner one (model TBC but it's a 185mm tunnel so probably the SE100 assuming it will fit in the space), and add a suitable 24V battery adjacent to it to eliminate the long cable runs. Use the existing cables as the charging circuit for the new battery. While I'm in there I might also rewire the windlass to consume its power from that battery.

Any obvious flaws in this plan? Any insight or better suggestions welcome.

Basically, sounds like a good plan. AGM batteries are well suited here. Definitely run the windlass from the same batteries.

Using the existing cables to charge the bow batteries, how ?

 

[Sticky Fingers]

Basically, sounds like a good plan. AGM batteries are well suited here. Definitely run the windlass from the same batteries.

Using the existing cables to charge the bow batteries, how ?

Ref the charging… details hazy (ie, I’ve no idea at the moment) but as the existing AC charger and the alternators are in or near the lazarette, it seems sensible to reuse these cables rather than running new ones. Presumably I’d need to disconnect from existing supply and then install something to split or divert the charger current to the new bow battery.

 

[Sticky Fingers]

Will you be charging from the alternator or with a DC/DC charger? You don't need the heavy cables but guess it would be a nightmare to run new lighter ones.. Otherwise makes sense doubling the power of the thruster. ….

Bit of a wallet hitter for you but good future benefit.

As above, not sure at the moment. Wallet hitting is all happening early on, makes sense to get the most use from any upgrades.

 

[vas]

Graham,

have you measured voltage at the bow thruster terminals when in use vs when sitting idle?
That could give you an idea of either thruster or cabling being inadequate.
Mine is a 5kW on a 43ft in 185mm tunnel and it's reasonably strong - wouldn't want it stronger tbh.

Having said that if fe voltage drop is serious, cabling update is going to cost an awful lot. I was lucky to get some seriously thick cables and had the boat in pieces at the time so routing was easy...
If voltage drop is serious, I'd get the 2XAGM batteries first, find where to fit them in the bow, find how to charge them and rewire the bow thruster and see how it performs!
It may be enough of an upgrade to skip replacing the mechanical bits for a while (or for ever!)

cheers

V.

 

[Sticky Fingers]

That’s a good idea I’d prefer not to run new cables from the existing batteries. Better to add a new battery.

 

[vas]

agree, maybe worth getting someone to check the brushes on the motor (assuming there are any!) clean/check make sure it's as good as it could be, new batteries nearby and check for any improvement. If not, you go step 2 and replace the mechanical bits
Is it twin propeller and how many fins on each prop?

 

[Sticky Fingers]

agree, maybe worth getting someone to check the brushes on the motor (assuming there are any!) clean/check make sure it's as good as it could be, new batteries nearby and check for any improvement. If not, you go step 2 and replace the mechanical bits
Is it twin propeller and how many fins on each prop?

It’s a three blade single prop, only 4HP / 3kW so probably at best it’s barely adequate, and hampered by long cables too.

 

[vas]

ah, in the first post you said 4kW, if it's indeed only 3kW I'd replace it no mater what!

 

[Sticky Fingers]

ah, in the first post you said 4kW, if it's indeed only 3kW I'd replace it no mater what!

It’s 4HP 3kW, now corrected

Yes I came to the conclusion pretty early on that it’s time to bite the bullet and replace it.

 

[volvopaul]

Many years back I fitted one to my Princess 410 , I fitted 2 batteries up front under the bed so was a very short cable run and used the anchor winch feed cables to a diode to charge the batteries , I always had to switch on the winch breaker to charge the batteries , the engines also fed charge when running , worked perfectly.

 

[PaulRainbow]

Ref the charging… details hazy (ie, I’ve no idea at the moment) but as the existing AC charger and the alternators are in or near the lazarette, it seems sensible to reuse these cables rather than running new ones. Presumably I’d need to disconnect from existing supply and then install something to split or divert the charger current to the new bow battery.

Move the existing cables to some terminal posts. The battery charger could be a 3 output model, i'm assuming you have one set of batteries for the engine and another for domestics ? Alternator charging could be done by fitting a 3 outlet Victron Argofet, instead of what's there, depending on what that something is.

 

[Sticky Fingers]

Move the existing cables to some terminal posts. The battery charger could be a 3 output model, i'm assuming you have one set of batteries for the engine and another for domestics ? Alternator charging could be done by fitting a 3 outlet Victron Argofet, instead of what's there, depending on what that something is.

Yes, got a bank of 4 x 110Ah domestics, bank of 2 x 125Ah engine start. Assuming charger is 2 output but I’ll find out on Wednesday when I go and have a look. Plus a genny start that’s a 12v with its own charger.

 

[Driver]

I had a Side Power SP65. Upgrading to the latest impellers made it equivalent to SP70, according to Side Power. Also, the SP 100 motor will bolt straight on to the existing unit, but check its the right model motor by telling the supplier what you are doing.

 

[PaulRainbow]

Yes, got a bank of 4 x 110Ah domestics, bank of 2 x 125Ah engine start. Assuming charger is 2 output but I’ll find out on Wednesday when I go and have a look. Plus a genny start that’s a 12v with its own charger.

Can't think of a 2 outlet charger, 1 or 3, yes.

 

[Sticky Fingers]

Ok so hopefully it’s a three output. Sod’s Law says it’s a single for the domestics, and the engine batteries are charged by the alternators….! I’m going down to the boat tomorrow to check this out.

 

[petem]

Think I'd try adding the battery and servicing the BT motor before fitting a larger one.

 

[Sticky Fingers]

Think I'd try adding the battery and servicing the BT motor before fitting a larger one.

That’s an option together with changing the BT prop to a more efficient one, would be done as phase 1. Drawback to a new BT aside from the cost is that butchery of the under-bed storage cabinets is required to fit it in physically, it’s much bigger than the current egg whisk.

 

[Bouba]

You can go further and change the blades....improved blade shape and number of blades can give more grip in the water