overheating

Check this out as a place to start for your overheating. There have been several recent threads too, so look around a bit on this site:
http://www.skidim.com/Faq_TROUBLESHOOT.asp#RWTS

Impellers and air leaks on the suction side of the system are common culprits.

The last owner said he used 40 weight so i did too.what ddoes your usually sit at when at idle?i thought it should be stable, like a vehicle.
And where might the impeller be found at?

On your overheating problem...Like Bri said...it SOUNDS like there is a leak somewhere, so when youre idling, it could be sucking in air so less water is getting to the motor, then when you throttle up and get moving your sucking in more water so it cools down. This happened to me once and it was a crack in my fresh water filter cover that I couldnt see easily and it was sucking in air. I finally notided that it was only half full at idle and my motor heated up but then as I got underway it filled up and the motor cooled down. Luckily it was an easy fix.

I dont think its your impeller because they normally shred when they go bad and when that happens...well its normally just bad news. But it doesnt hurt to change it now. I'd start lookig for a leak in the fresh water cooling department.

when the oil is really heated up my pressure is like 30 psi at an idle and 50 while running. Thats with 20W50. Also I dont think electric oil pressure gauges are always super accurate but 20 seems like enough at an idle. Just keep an eye on it I would say.

Plus the tools to change it if out on the water :D