I think the key to thruster is definitely thrust. Insufficient thrust and you run the thruster too long. That is a lot of draw and heat. I understand that if you have lay on them they burn out quickly.
We have a Lewmar bow thruster with a 9" diameter propeller (installed before we bought the boat). The thrust selected will be influenced by the prop size and required hp to turn it. It looks as though installing a thruster tube >9" in the front under the bed would be difficult so I think that is how they landed on the size. The stern propeller must match the bow propeller diameter or the boat won't track laterally when both are engaged.
The 9" is ok - don't go any smaller.
The bow thruster in our boat was was originally selected based on cross tube size and limited capacity for battery storage in the area. The Lewmar thruster guide http://www.lewmar.com/downloadcatalo...8276&lid=25667
has a wind force factor by hull type & then you cross that to your length.
Hi Wrasse.
On our 46 SCB we ha a Side power SP75T on the stern and a SP95T in the bow.Tubes are 7.28 in in diameter both are twin props and are running on 12 volts. These thrusters allow for the boat to move side to side perfectly. I find they are more then adequate in any conditions I have met so far.
I hope this info is helpful and not to late for you.
4600 SCB Bow and Stern Thruster Size?
Linear Mode
