What Size And What Make Stern Thruster

[AndieMac]

It saddens me that anyone who could own a 55' twin screw yacht could find it hard to handle a boat on both motors alone without having to resort to a stern, or for that matter, bow thruster.

A quick boat handling course or even an ICC Power would sort that out and give the helmsman an infinitely finer experience when out on his boat. Its amazing what you can do with the slightest input from one engine and a pre-selected helm. The most important thing they teach you is think ahead and only ever use slight movements of the throttles, nothing rushed. If you aren't going fast enough to do any damage, you can always fend off if it all goes wrong. Just keep inputs to the minimum and only blip the throttles, even an Azimut 55 shouldn't need any more than a tickle of power, in the right direction.

Maybe this is the reason why so many of the larger boats just sit on their pontoon like an Olympic flame, never going out.

It's a good thing we are all different....isn't it?

 

[Renegade_Master]

"Its amazing what you can do with the slightest input from one engine and a pre-selected helm"


pre selected helm on an AZ55 ? .............oh I see just reaslised you meant pre-selected to midships sorry ignore me

 

[aviator]

Always stack the cards in your favour, finance permitting, and fit a stern thruster.

I have never regretted it for those little adjustments and stuff like coming straight out sideways with tight berthing.

Also when it comes to selling 'loaded' boats are easier to sell.

18 days without rain in the South. Hope it continues into next week!

 

[theguvnor]

Ihave only one arm & (thankfully) only one knob !

Me big round fender is my bow thruster and quite frankly, I've only got two arms, so could not handle more knobs.[/QUOTE]

 

[Nick_H]

It saddens me that anyone who could own a 55' twin screw yacht could find it hard to handle a boat on both motors alone without having to resort to a stern, or for that matter, bow thruster.

Wow, I bet you could drive an aircraft carrier blindfolded.

 

[MapisM]

Of course I did guess at the time this arrangement (hyd. thruster) was basically down to a poor installation/set up on this vessel, and not typical of this type of machinery. As MM says, they are highly regarded.

Yep, it sounds like the system wasn't properly sized, to start with.
Either the pump has to be good enough to drive the thruster also when idling, or there must be one pto/pump on each engine.
Btw, the latter solution has the advantage of full redundancy, in which case it's acceptable that in an emergency, running on just one pump, some RPM increase is necessary to get full power.

Anyway, in the situation you're describing (heavy D boat, massive windage, hard running X tide/wind), the olny alternative which is better that the hydraulic thruster is the azipod, as used in some commercial vessel. Surely not an electric b/t.

 

[rubberduck]

Wow, I bet you could drive an aircraft carrier blindfolded.

I checked his profile but he has failed to specify the type of cruise liner he owns.

 

[jfm]

the olny alternative which is better that the hydraulic thruster is the azipod, as used in some commercial vessel. Surely not an electric b/t.

Azipods are frequently electric MapisM ;-)

 

[Deleted User YDKXO]

Just signed for a Azimut 55 and want to fit a stern thruster so need opinions on what size and make to go for please.
Thanks Mike

I never thought I'd say this given that I've said on this forum in the past something along the lines of sternthrusters being for big girls blouses but I've got one on my new (to me) Ferretti 53 and actually it's quite a useful piece of kit albeit in the nice to have rather than essential category. It's true that you can move the stern of a boat using the engines but on my boat, there's quite a kick when you engage gear, enough of a kick to throw a crew member off balance. The sternthruster moves the boat with a more gentle motion. Also when you use the engines to move the stern sideways, you are pivoting the boat around a point about one third of the boat length aft of the bow which means that when you push the stern away from a quay using the engines you are also pushing the bow onto the quay so you usually need fenders on the bow when you do this. When you use the sternthruster, the boat pivots about the bow and the bow is not pushed onto the quay; it is then easier to use the bow and sternthrusters simultaneously to move the boat off a quay rather than the bow thruster together with the engines.
As I say, a sternthruster is not essential. You can manouvre a boat any which way using engines and bow thruster but a sternthruster can make it just that bit easier though I agree with jfm that it is a potential danger to swimmers

 

[MapisM]

Azipods are frequently electric MapisM ;-)

Yeah I know. I didn't say hydraulic azipods, in fact.
Completely different animals compared to electric B/Ts, anyway.
Besides, I bet you'd also go for an hydr rather than an elec b/t, if given the choice, wouldn't you...?

 

[MapisM]

easier to use the bow and sternthrusters simultaneously to move the boat off a quay rather than the bow thruster together with the engines.

I have to agree on this one.

 

[jfm]

Yeah I know. I didn't say hydraulic azipods, in fact.
Completely different animals compared to electric B/Ts, anyway.
Besides, I bet you'd also go for an hydr rather than an elec b/t, if given the choice, wouldn't you...?

Well I guess my point was that you criticised elec b/t above and actually it is not the electric-ness of them per se that is the problem. It's that they are not made well. To keep cost down, they use cheap motors and often do not engineer any solution to the heat build up. If electric b/ts were well made, like electric azipods that run 24/7 on ships, they would be fine. My Sliepner electric b/t (11hp, 300amps) is well constructed and will run for >60 seconds. In fact I have never had it (two of them) cut out in 6 years. But a lower quality electric b/t would cut out at 60 seconds for sure

In the 60 foot/11hp size range I would always have electric b/t, so long as it is a good one like sliepner. Above that size, there is nothing good enough for leisure boats in the electric market so you need hydraulic

Hydraulic only work when engines running. That is good for swimmer safety but bad if you want to swing the nose of the boat to a swell at anchor when everyone is having dinner. also some hydraulic installations on mainstream boats have pto off only one engine. (another cost saving, like cheap electric thrusters). If you lose that engine you have to drive the boat on one engine and no thrusters!

But yes, on a bigger (than 60 foot) boat I would have hydraulic, with 2 ptos if possible, because there is no electric solution on the market

 

[Hurricane]

though I agree with jfm that it is a potential danger to swimmers

Our thrusters (both of them) run off the engine batteries.
So, its just a matter of principle to switch off the engine isolators (using the little remote switch on the DC panel) whenever the engines are off. I think this is a good procedure anyway (egnine room fans run on because they are fed from the service batteries). This kills the feed to the thrusters so that they cannot be inadvertently operated.
Well, thats what I do anyway.

Our old Sealine had separate bow thruster batteries which weren't interlocked with anything - I foget how the stern thruster was wired but I'm sure you are right in saying - be careful.

 

[MapisM]

Well I guess my point was that you criticised elec b/t above and actually it is not the electric-ness of them per se that is the problem. It's that they are not made well....

Yup, different animals, as I said. Agreed also re.the double pto/pump, as per my previous reply to AndieMac.
It's not just a matter of size, though. Not sure about which boat AM was talking about, but I've seen 60' trawlers weighing 80 T or so, hence obviously fitted with hydraulic thruster.
But I've also been on a much less extreme 62' for instance (semi-D, GRP), with a Wesmar hydr system for the stabs and thrusters (25hp each). Looovely bit of kit, built as nothing else I've seen around (the same can be said for their electric ones btw), and very nicely combined, if you think about it: you don't need thrusters when you need stabs, and vice versa.
This boat is now being offered at a very tempting price btw...

As an aside, good point re.swinging the bow against a swell with a leccy b/t while anchored, I never thought of such usage.
I normally yell at the crew in these circumstances. It works a treat...!

 

[jfm]

So, its just a matter of principle to switch off the engine isolators (using the little remote switch on the DC panel) whenever the engines are off. I think this is a good procedure anyway (egnine room fans run on because they are fed from the service batteries). This kills the feed to the thrusters so that they cannot be inadvertently operated.

That makes good sense, and I agree it solves the safety point becuase there's no way an enquiring 5 year old (say) would manage to turn on the isolators AND then operate the stern thruster. But you are knowlegeable and experienced, and you understand the architecture of your boat's electrical systems. I reckon it is still worthwhile pointing out this hazard now and again, just in case anyone who boat with kids inadvertently relies just on the double-on-buttons safety feature on the joystick control panel

 

[AndieMac]

Not sure about which boat AM was talking about, but I've seen 60' trawlers weighing 80 T or so, hence obviously fitted with hydraulic thruster.

This example was a 50' steel converted fishing trawler, apparently approaching 70 T, but of truely massive proportions in every way (fugly in every sense of the word).
The inexperienced owner had spent a small fortune, including a complete machinery space replacement.
Changed the old Gardiner 6LX motors for new Cummins 6BT's (200 hp), which felt like a couple of egg beaters when manoeurving the big lump, no useful thrust in such a heavy vessel.
She has been laying unused for a few years now, perhaps a useful story for another time on the forum, as an example on a 'how not to' subject.

Sorry for the drift.......

 

[kcrane]

That makes good sense, and I agree it solves the safety point becuase there's no way an enquiring 5 year old (say) would manage to turn on the isolators AND then operate the stern thruster. But you are knowlegeable and experienced, and you understand the architecture of your boat's electrical systems. I reckon it is still worthwhile pointing out this hazard now and again, just in case anyone who boat with kids inadvertently relies just on the double-on-buttons safety feature on the joystick control panel

No need to rely on either the double-button or isolating the batteries - both my thrusters have big red buttons reachable in the lazarrette (hit with your fist size) that isolate them, click the red button back up to enable them again. I assume they all have that?

 

[rubberduck]

No need to rely on either the double-button or isolating the batteries - both my thrusters have big red buttons reachable in the lazarrette (hit with your fist size) that isolate them, click the red button back up to enable them again. I assume they all have that?

Mine do, sidepower fitted by osmotech.

 

[jfm]

I assume they all have that?

Nope. That is quite basic. Many builders incl Fairline fit isolators in the lazz or similar which can be operated locally in the lazz by clunking the big switch but also remotely by solenoid via a switch on the elec panel on the boat or the dash

 

[fergie_mac66]

Big enough not sure what make