Last week I got the boat out and clean it up (03 Ranger-Mercury 225 efi -0t467450) hooked up the water to the foot (had the low water pickup blocked off) and started it up. After about 2 minutes I got the long beep (hot engine) so I turned it off. Smart craft was also saying water temp was high. I thought I might not have had the water pressure turned up high enough so I turned it up more. Restarted the engine and no more alarm - ran it for about 10 minutes at idle.
A couple of days later changed the plugs and the water filter, I then wanted to check and make sure it would run so I hooked up the water again and got the long beep again (smart craft again showed engine temp). Let it sit for a few minutes and restarted and no more beep. Again thought that it was hose pressure (from house).
Went to lake yesterday and let boat idle at dock for a few minutes, idled out of no wake and just when I was going to take off.....beeeeeeep - smartcraft again said engine hot. I turned it off, waited about 1 minute and turn the engine on (not running) and looked at smartcraft - temp was at 160 and coming down -when it got to 125 I restarted engine and temp went to about 100 and then stayed.
I have a good pee stream, it was not hot when touched - water pump replaced last year. Someone said it's my t stats, and have been told it's my poppet valve.
Also had 3-4 psi at idle and close to 20 at 5000 rpm.
Can you give me a couple of things to look for.....also my t stat housing are smooth (was asked that). Thanks John
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... except that the Smartcraft reading is actually "essentially an average of both cyl. head temp sensors". 
