Temp alarm question

[wellcraftv20step]

Morning all,yesterday was the topical day in a boat owners life.. I charged my battery ,hooked up the muffs and started my 97 Yamaha 250 ox66 ,she fired and ran beautifully until after the rpm's dropped then I heard the temp alarm going off so I shut her down. Water seemed to be flowing from the pee hole normally. But I always assumed even with a bad pump you'd never know the pump was bad because it's actually under pressure from the muffs ????? I removed both thermostats as I had planed on doing anyway. Out of curiosity I tested both thermostats by suspending them in a pot of water at about 180 degrees. I realize the water was to hot to start with but I noticed one thermostat opened slowly and the other litteraly poped/snapped open .is this an indication that the one thermostat was bad? I'm running out to pick up a new impeller for the lower unit and thermostats.

[SkunkBoat]

they opened, therefore they are likely not the cause

[phatdaddy]

Yamaha's usually run a little warm on the hose

[wellcraftv20step]

Thanks guys, I was not aware of that phat. I just ran the same amount of water I used to run with my Johnson and evinrude. After I do the regular maintenance I'll give it another try !

[THEFERMANATOR]

They should open fairly quickly once they hit operating temp. If one is dragging open, once under pressure it may not open at all. If there out and unknown age, change them to be safe. And I'm a stickler for oem for parts like pumps and stats. Had to many aftermarket impellers spin for my liking, and had some aftermarket stats corrode out in just a few years, so I stick to oem there too.

[steplift20]

On a mercury that's what I have you have three excuse me I mean four things that could go bad Thermostats lower water pump and poppit valve and what about the sending unit? Do you have a poppit valve? Is it clogged by the water intake? If it's pissing out of the hole I think you illiminated that , let us know how you make out, I'm going to open mine next week I hope all goes well I will tell you I remember a friend of mine had a problem with over heating he had a even rude and I think he told me it was a oring that he forgot to install

[wellcraftv20step]

Well I changed out both thermostats and ran the motor for about 25 mins with no alarm sounding .im wondering if phat was rite about the yami's running warm on the hose!!! I ran the hose wide open today.ferm I am also a believer in oem Parts.and I'm absolutely aware of the poppet valve, I've never done one before so I'll read up on it .i hope the level of difficulty is not to bad

[steplift20]

I will tell you one thing, once the heavy hitters start advising you your getting the best it's like that song We are family Am I showing my age? Lol I hope not I only wish I knew a fraction of what they know Maybe some day

[steplift20]

I changed the poppit valve once I did it wrong the first time cause water was coming out of where I put it than I redid it again and it turned out good Not yo hard from what I could remeber