i think i found the problem
@Cobra Jet Steering LLC - you were right, again. seems to be the
Engine Thermosensor.
at Lake Tarpon, FL today (air temp 64*F, water temp 68*F):
i ran the boat at idle and No Wake for about 10-15mins at the dock, taking temps on the exhaust and anywhere i could get a good reading on the engine itself. both engines were reading similarly on the IR Thermometer to what i was getting in the driveway (the starboard was again running about 10*F more in each area, except it was about 20* higher on that one head area). then i ran both engines at WOT. the boat ran great - i was actually starting to worry the chilly day was going to keep it within normal limits. the port engine finally tripped the water temp light on the dash but did not limit me to 3000RPMs. it just sounded boggy and lacked power. again, everything was about the same temperature: 10*F warmer on the starboard engine; 25-30*F warmer on the starboard engine at that one area of the head only(!!!). it cooled and i did it again with the same results. the results were so what i expected that i didn't even bother to write them down.
then i hooked up the laptop/YDS and ran it until it threw the error again: this time, the live Engine Temp Sensor in the YDS turned from the normal blue to an orange with a reading above the 266*F threshold ...maybe 268*F or something. letting it cool for a few minutes to drop below 266*F at idle, i did this a couple times with the same results. then i ran the same test on the starboard engine. it was holding steady at 145-155*F at the Engine Temp Sensor. all IR readings between the engines were what i expected/normal. obviously, running the engines at a lower RPM following WOT (rather than shutting them down) helps remove a lot of heat. also, it seems that running the boat with the throttles in the forward detent helps cool the engines much faster than the "Neutral" - probably because you're flushing the exhaust water well away from the intake.
with it likely narrowed down to the Engine Thermosensor, i started unplugging them on both engines while idling to monitor the YDS temps for differences. the port (problematic) engine's sensor was erratic - once plugged back in, it would bounce around the reading it had before the unplug and usually settle on a few degrees higher/lower of that reading. the starboard engine's sensor would very quickly settle into the reading it had without bouncing around it. and again, there was a 100*F difference between the two in the YDS. since i was alone, the one test i wanted to run but couldn't was watching the YDS while at WOT to find at what temp the port sensor would just go haywire. in any case, i'm fairly certain this is the issue. i even ran it the length of the lake (how long it took to overheat each time; about 5miles) with the Thermosensor unplugged - it was throwing the Port Engine idiot light (3 blinks), but ran beautifully. on the GPS, it was running 46-48mph against the wind and 50mph with it (winds: NNW 15mph). once near the dock, i plugged it back in so i could use the No Wake mode - no lights/errors.
i think if i remove the two water hoses on the case near the engine anode, i should be able to get a wrench on the sensor to remove it.
