Thruster questions

[tugnnaweigh]

Bought a 25 in December, having big fun, need a little thruster information/opinions. Mine sound like a box of rocks, including sending vibration through the boat! The front more so than the rear, although some of that may be due to being closer to the front one.
They also slowed significantly when I engaged both. Looked them over on the trailer, everything is clean in there, no side play in the propeller shafts. I did the "connect the thruster battery to the house bank" thing and that cured the slow down so my questions are:
What do your thrusters sound/feel like?
What's the maximum length of time they should be run each time they are actuated? Thirty seconds comes to my mind.
I see on here it's a chore to replace them and I'm trying to get an idea of the life left. Thanks for the help, rich

 

[bbrh842]

Every thruster I have ever head is noisy. They make a quite disconcerting loud grinding noise, best I can describe it. On my R25, they also slow noticiably when you engage both at the same time. I don't think the battery has the capacity to deliver adequate voltage to both at the same time. Seems OK to run both at the same time, but they will not deliver the same thrust as using one at a time. The book says three minutes max continuos operation. If run too long, they will get hot and shut down until they cool off. My rear thruster came on all by itself, and ran until the thermal switch shut it off. BUT, by that time the motor had already been damaged and had to be replaced. My experience with docking and undocking is, you seldom need to use the thrusters for more than 20 or 30 seconds, if that long.

 

[aginglawyer]

One additional bit of thruster advice, learned the hard way: Don't reverse the direction of the thruster until the thruster has completely stopped. If you try to reverse it before it has stopped, you risk breaking the shear pin; happened to me a few times before I learned.

Allan

 

[LADYBUG TOO]

The manual for the Side Power units on our 2009 R-29 say not to run both at the same time. If you have a power meter installed you will see a heavy voltage drop when the thruster is engaged. The controller will also limit time on to prevent overheating. Some newer models have a separate battery for each thruster. We have a single battery so we changed to a Group 27XXHD Exide with 1000 cold crank amps. Thruster performance improved dramatically. I would check your thruster props to make sure nothing has happened to them. Also, running out of water would cause higher RPM and possibly account for added noise.

Pat & Carolyn
Ladybug, Too

 

[pugtug613]

When I need to spin 90 degrees, I always use both thrusters. One port and one starboard. Are you saying I should not do that? After 20 - 30 seconds the RPMs change. Then I let go the joy sticks for 5 seconds and go again, if needed.

 

[HRowland]

You can use both thrusters, on our 27s I have never seen a recommendation not to use both simultaneously. Initially the ACR (Automatic Charge Relays) are paralleling all of your batteries so the single Thruster battery is supplemented by your House and Engine banks. After a period of running both thrusters the ACRs open due to the reduced voltage, they believe that charging has stopped because the sensed voltage is below their threshold. Once the thrusters are stopped the voltage rises again and the ACRs close the connections to restore charging all banks from the engine alternator.
It is actually a little more complicated, the ACRs have different close and open time delays depending on the sensed voltage. Visit the Blue Sea web site if you want the gory details!

I have combined the house and thruster banks into a single 3 battery bank. I added 600A bus bars to balance the current draw from the three batteries and do not have any issues with electronic dropouts when both thrusters are used. Since the engine alternator is connected directly to this bank it supplements the current required by the thrusters. Even at idle RPM I have seen the alternator provide over 100A.

Howard