T&T: Bow Thruster

[Ownyacht at aol.com]

I have a 7hp Side Power bow thruster on my 2000 42' model boat. I have  
monthly diver services here in SW Florida. The barnacles are not too bad this  time 
of the year.
 
The last couple of times that I have used the thruster for long enough to  
turn the boat 360 degrees the breaker has tripped. I always use short bursts  
combined with forward motion using the rudder rather than letting it run for the 
 complete turn. Also it doesn't seem to have its normal "umph".
 
The battery seems OK. It is a 3 year old Lifeline AGM that it shares only  
with the windlass (which gets very little use). I have checked the level of gear 
 oil in the remote mounted fill bottle and it is half full.
 
Any ideas what is causing this? Would a weak battery cause it to trip the  
breaker? I assume that the thruster is getting hot causing the  tripping.
 
Thanks
 
Doc
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