I just had my engine rebuilt and took my boat to parker this weekend. I usually ran 180 water temp , but this weekend i could get below 205.If I let it idle it would creep pass that . I plumbed every thing the same , the motor ran perfect . My jet worked fine , I checked the intake on the jet for any blockages . BTW I Run Logs with snails and a straight line off the jet with no valve.

You'll want to run a valve of some type on the inlet from the jet, even if it is wide open all the time.  If you happen to blow out a freeze plug and have no way to shut off the flow of water into the boat it WILL sink. 

Did the engine get throughly washed before/after the machine work was done?  I flushed a lot of dirt out of my block before it went to the machine shop.   I blew some more out after it was dry, then I washed it out again.

Check your air/fuel mixture. If youre running to lean the motor will run hotter than a "fat"/rich motor

Also double check your timing.

 I'm going to take a shot at this one. 

 First, how is your water routed ?  Does it go from the pump to the motor first then to the logs, or from the pump to the logs then to the motor ?

 If its going to the logs before the motor (to preheat the water), you might have a tuning issue with the new motor causing realy high exhaust temps now. That would cause the water to be overly hot before it even gets to the motor.

 just an idea.   

Pulled my motor last week. full of dirt and sand and I mean alot . I have a fancy dancy seastrainer 2. guess I'm going to need a sand strainer $$. boat never saw above 135, a whole other issue I'm fixin to fix. But with small diameter water lines I can see it causing a motor to run hot. Supprised mine didn't but at the same time, I went over kill on the cooling system and now have to bring my temps up.