1998 Mercury 200 HP EFI SN #OG606131
Hello, I’m having an overheat alarm at ¾-WOT. A steady BEEP. Motor has a new water impeller and housing aswell as new fuel pump installed by Mercury dealer last month before I boughtthe boat since it sat for 4-5 years without use. I have deleted the oilinjection and alarm module myself as I was having issues with it. I now run non ethanol fuel with 50:1 premix as well as Techron marine at 1oz per 10 gal.
I have installed new thermostats and poppet valve assembly myself and that has helped a bunch as the alarm was going off much sooner before. Also, my water pressure at idle with boat in the water is at 12-15 psi and quickly jumps to 30+ psi at anything over 1,500 RPM and has a great tell tail pee stream. I am able to get boat on plane and run at ½-3/4 throttle now and no alarm. Yesterday I ran it at WOT until alarm came on and shut it down and pulled the cowl off and took infrared thermometer readings and got 180°F on port side head and 165°F on starboard side right at temp sensor. I think It’s fair to say there is a blockage somewhere and need some ideas of least invasive first to start with please.
Also, I think I noticed one early morning while on plane at around ½ throttle, there looked like small puffs of smoke/exhaust coming out around the telltail or midsection of motor. Was only able to notice it because the sun light was just right.
So where should I start? Boat is 50 miles away in storage and would like some ideas on what to check and where to start if I have to bring it all the way home and take it back with no trailer brakes. Any ideas and help would be greatly appreciated!