Question about thermostats and overheating..

[stingraymax]

Hi,<br /><br />I have a 99 johnson 90Hp and had some serious problems with this engine, I bought this second had and it had a scored piston,(I don't know the reason to this ) so I took it in to have it rebuilt.<br />They replaced the bad piston and all the piston rings on the rest of the pistons.<br />The walls were still ok.<br />Replaced waterpump, VRO unit and thermostats.<br /><br />But now when I take the boat out it runs perfect with stong tell tale as long as I don't go WOT if I stay below 5000rpm it is ok but when I go to WOT after about 1 mile the overheating alarm go's.<br />I took it back to the mechanic and hey just took it for a spin and indeed as long as it stay's under 5000rpm no problem, WOT after a while overheats...<br />He took the stats out and it doesn't overheat anymore.<br />He tells me the water presure is great and there is no obstruction in the engine, now he wil try to take a bit of the sring from the stats of so it opens a little bit more or wil drill the stat seating i the block a litle bit to get more water in at high temp.<br /><br />anybody had this before or knows what this might be ?<br /><br />Thanks