Shouldn't run it until alarm is hooked up. With missing t-stats there is a good possibility there was an issue.
Temp sensor comes out of the back of the head....note wire color.
I was thinking of an IR gun like this.
Engine was designed to have t-stats. Perhaps you have some clogged passageways. Do you have any temp readings of each head?
Is your overheat alarm working?
Might want to start all over with idle screws. Start 1 1/2 out from lightly seated. Then adjust each one. Then get it on the water and bomb around a little if it's running ok. Then dial in the carbs again for low idle fuel mixture.
You can just undo the ground kill wires than and spin it over. Should tell you what you want to know.
By the way, if it gets windy out make sure you bring your kidney belt!
I knew an owner of a Yamaha/Evinrude/ Grady White dealership and he said when he was at a dealership could convention he was boasting about how he had a customer with 8500 hrs on a four stroke yamy. Next thing you know everyone was boasting about a customer with lots of hours one even claiming...
Doesn't this motor have a main wiring harness plug back at the motor? If so unplug it, hook up your spark tester and jump the soloniod.
That should produce spark.
By the way....that tri hull weighs more than 500 lbs.
Everything looks ok....when it over rev'd did it sound like it was over revving?
Might have an electrical issue that made the tach read incorrectly and bog the motor down.
Somewhat guessing but it must be a dirty contact somewhere. Key being on is giving it more power and going down requires less amps than going up.
My motor the relay steals power from the hot side of the starter solenoid. Look at and clean all contacts including ground.
Weird one.
