Tuesday, January 24, 2012

Big hole in the boat

A Sidepower bow thruster going in at the KKMI yard last year.  This unit is a 24V SE-100.  

This unit is rated at a little over 8HP.  The yard did a great job on the installation and were able to place the tunnel very low in the bow to reduce cavitation.  There are two 12V Lifeline AGM batteries dedicated to the 24V thruster.  The batteries were originally isolated from the engine start bank with a Newmar battery isolator but I have since replaced this unit with a Balmar Duo Charger.  I found that the thruster bank was never getting fully charged because of the voltage drop across the diodes in the Newmar isolator.  The new set up is nice because the Duo Charger will allow the batteries to fully charge and source 30 amps when needed (thruster in operation) from the engine start bank.  Additionally, the Duo Charger will limit charging to 30 amps so I didn't have to run huge wire through the boat.

I opted for the flat panel control at the helm instead of the joystick.   We also have a wireless remote.
Overall thoughts on the bow thruster.  It is certainly a luxury item.... and an expensive one at that.  I'm glad we have it though.  Shindig is big heavy boat and we are in and out of marinas all the time.  Knowing that we have the bow thruster if needed gives me the confidence to get in and out of tight spots.  Also, Shindig does not have much prop-walk to help with maneuvering.  With our prior boats I counted on that a lot to spin the boat or suck the stern into a side-tie.

We have also found that it buys us time when tying up.   It is usually just the two of us when docking and Nancy does the jumping.....  She can secure a spring line and stern line while I can hold the bow of the boat against the dock with the thruster.


  1. How much additional drag does that opening cause? It seems like flow coming off of the surface just ahead of the hole would eddie into the hold, and the trailing edge would also offer some additional resistance...

  2. There is some drag to be sure but there is a bump that is built up on the leading edge (not shown in the photos) that helps some. I suspect that the thruster would hurt performance at slow speeds and be hardly noticeable at hull speed.