Optimax thermostat ?

[staylor]

... and opens at around 1200 rpm in a 150 Opti. If I had a stat stuck open, then I'd never be running a normal 145 degrees at idle- and the shop manual clearly states that the stats open at 145. It also states that the bypass poppet opens at about 1200 rpm, when the pressure in the cooling system increases with rpm to 4 psi. It is stated very plainly in the text that "above 1500 rpm, water flow is controlled by the poppet", not the stats. I would assume that the temp pick up for my 150 is downstream of where the poppet is and reads the total flow from the stat controlled loop and the poppet controlled loop, so the Smartcraft gage is reading an average temp of both a cold and a hot water flow above 1500 rpm after the poppet opens. I would also expect that the stats are still holding the head temp to 145 or so- since I know the stats are functioning when they hold the temp properly at idle. Per the shop manual, if you read around 145-150 constant temp at idle, then the stats are fine. If you read less, then the manual suggests checking the poppet valve, after you check the stats for opening temperature. The question is- are you fellows reading normal idle temp of around 145 degrees- if so, then your stats are fine- at least according to the 2001 Optimax shop manual for 115-150 hp Optimax. I can't say if the big blocks are the same- do any of you fellows have a shop manual to check this- it's a quick read, only 3 pages for the cooling system checks, along with a fold out drawing. All I know is that my motor's never had any troubles, does an awful lot of Musky trolling through weeds and muck, and has yet to foul a plug or even load up after trolling. I back flush it thru the hose connector on the lower unit once a year as normal maintenance.
Doug