Overheating 5.7 OSXi

Question
Engine 2005 Volvo 5.7OSXi  with a DXP outdrive (composite). I have 50 hours on the boat.  Last year I would overheat now and then at slow speeds. I would run the boat to 30mph and no overheating. This spring I replaced the fresh water pump impeller (one of the vanes was cut in half and I thought this was root cause), thermostat, cleaned the heat exchanger and replaced a "from the factory" crimped hose from the heat exchanger to the right-hand exhaust manifold. It still overheats! Thought I may have the fresh water impeller in backwards. I changed it no change. I have ensured there is no blockage from the drive pickup to the fresh water pump, and that the new thermostat is opening. I still don't seem to be getting water into the exhaust manifolds and the engine continues to run hot.  I've talked to several dealers, but no one in Michigan knows anything about the XDP drive.  I'm going bald pulling my hair out!!  Help please!

Answer
Hi Brian...Thanks for selecting the undersigned to reply to your question.

I'm not a mechanic, but it definitely sounds like you've got a restriction or blockage of some sort and water is not properly circulating throughout the journals. Have you checked the colour of the engine oil? Have you checked to see if you're bilge is accumulating more water than usual, and is your pump being activated more frequently? Since local dealers don't have a clue, I suggest you contact Volvo direct by phone or online for qualified guidance.

Safe Boating
Ron