Hydraulic Bow Thruster question

[GCSI]

My #1 Gen is a 21.5KW Onan that powers bow thruster via power take off on front of gen. Near the back end of the generator, mounted on a bulkhead is a large (approx 2’x2’) electrical box labeled
“Bow Thruster Gen Unloading Contactor”. Can someone explain the function of the contactor?

 

[scottinsydney]

The bow thruster is powered by hydraulic fluid being pushed in circulation by the genset's PTO. The circulation of the fluid from and to the PTO is always the same direction.

Its likely that the contactor is actually a solenoid control that operates a reversing valve located within a manifold nearby and directs the the flow of fluid depending if you wish to go to port or starboard when the dashboard toggle switch is moved/pressed. Regardless of the switch position the flow of oil from and back to the PTO remains the same direction.

 

[Dan Mapes]

If it is truly related to unloading, it could kick the pump out of the loop to prevent stalling the genny, or, perhaps it drives a clutch between the pump and genny (my favorite guess). Do you have to "arm" the thruster by flipping on a master switch? Maybe the joystick drives the clutch regardless of the desired direction. It might be obvious if the genny is off, and the thruster joystick causes the solenoid to actuate but that may be inhibited with the genny off.

 

[Pascal]

2’ x 2’ sounds big for just a contactor…

What brand thruster is it? You don’t have the manuals and diagrams on board?

We have an ABT Trac system on the boat i run. The hydraulic system is powered by a pump on each engine and the starboard gen via a PTO. The 48kw gen will struggle for a couple of seconds when the PTO is engaged if the hydraulic system is activated.

In your case this maybe a circuit to disengage the PTO of gen freq and/or voltage drops below a set value

A hydraulic thruster uses quite a bit of power, I m even surprised it is driven by the gen and not by the mains. Our thruster is obviously pretty big on a 116 but so is the cummins 4BT driving the gen and that’s not enough to run the thruster. The PTO is only used for the zero speed stabs and the windlasses.

Call the thruster manufacturer if you don’t have the diagrams.

 

[GCSI]

 

[GCSI]

The box is 2x2, contactor is within box. ABT System. Normally, thruster will stall the engine if generator has any electrical load.
Consequently, I’ll run house load on Gen 2 and thruster on #1 if thruster is needed. Seems kinda Mickey Mouse that thruster can kill
Gen if Gen has any load. Was thinking function of contactor would be to shed e load while thruster is used and the contactor is wonky.
Plan on calling ABT and will report back.

 

[Pascal]

ABT track customer service is very good with phone support. Here in SoFl I used Advantage Marine Service in FTL. He really knows these system.

I don’t understand why they didn’t just put hydraulic pumps on the mains. It must be a pita to have to run both gens when maneuvering

 

[jmooney]

ABT track customer service is very good with phone support. Here in SoFl I used Advantage Marine Service in FTL. He really knows these system.

I don’t understand why they didn’t just put hydraulic pumps on the mains. It must be a pita to have to run both gens when maneuvering

I would like to install hydraulic pumps for a bow thruster but I don’t have a PTO pad on my transmissions . The only place on a 12V-71 is on the nose of the crankshaft and that would kill accessibility not to mention being expensive to install. As I have two generators , I thought about that installation, but even 20KW doesn’t have that much power at 1800 rpm . A 48 volt Westmar is my next choice.(25 HP)

 

[Captain Ralph]

12V71TA does not offer much with the second cam PTO used for the alternator.
The 12V71TI second cam PTO should be available on the engine not driving the stabilizers pump.

On our partners Hatt, the 48V Westmar works great.

 

[jmooney]

12V71TA does not offer much with the second cam PTO used for the alternator.
The 12V71TI second cam PTO should be available on the engine not driving the stabilizers pump.

On our partners Hatt, the 48V Westmar works great.

I don’t think that the pad on the rear of the engine can handle a bigger hydraulic pump than the stabilizer pump.

 

[Captain Ralph]

2 stroke DDC cam RPMs are the same as crank RPMs. Unlike 4 stroke diesels / half the RPM at the cam.
My thought is, why mess with the front DDC crank when the same RPM is available at the cam PTO?

But, the installer has to install and warranty his product. These are the rules that purchasers must go by.
Whatever I think may not matter.