Re: 89 xp 150 overheat (solid tone) alarm
That engine will set a hot horn when the head temps get up to 203 degrees. The horn will shut off when the temps go back down below 175-which is still way to hot. Your engine should run between 143 and 155 at idle. Probably just a stuck stat. Agree on the stats, replace them both. When you have the thermostat housings apart, also check the nylon pressure relief valves to make sure they are not heat-deformed. Hopefully, this will cure your overheating. If that does not take care of the overheat, you may want to pull the hot head and check the cooling passages around the cylinder liners. Specifically, the placement of the rubber water diverters. Make sure there is no restriction in the block by those diverters.