2002 225ox66 overheat alarm

[DennisJensen]

First run of the year and got temp alarm after about 2 min running at 3200 rpm. I shut motor off right away waited about ten minutes for alarm to shut off but it went off after about a min off running again I shut down used trolling motor to get to cabin glad I’m not far from launch. New lower unit installed just before put into storage last fall. Has strong stream from pee hole water pressure gauge has been off for last few years (I know shame on me). What should I check first? Third summer with boat I’ve never done anything with temp system sorry for wall of text

[McQuaig]

If it were me, I'd first check or replace thermostats and replace poppet valve (the design changed since 2002)...and definitely put a new pressure gauge on it.

[DennisJensen]

Is there a easy way to test them in the middle of nowhere atm. Thanks for the reply

[McQuaig]

Sorry, i don't know any easy way other than removing the thermostats and putting in a hot enough cup of water to see if they open. You would likely need new gaskets to re-install them (so may as well just put new stats in if they're original). The same idea with the poppet valve.

[DennisJensen]

Thanks a lot not what I needed on first day of vacation

[milligjg]

Strange, 1st trip out last Friday mine (2000 225) went off for about 20 seconds while idling around and when I hammered it again it went off and ran fine. I headed to the ramp though. I figured just idling around caused it. Hmmmm. This is the 1st Yamaha I have ever owned. Should I replace thermostats and poppet too?

[DennisJensen]

I talked to dealer he didn’t have thermostats on hand. He said I could run it without them til I could get some. Not sure if I like that. I did let it idle at the dock for about 5 min and the stream was only warm not hot at all. I didn’t check it when the alarm went off.

[04_triton]

just cut the wire to the alarm....that SOB wont go off again lol

[DennisJensen]

I got new thermostats today had 3 hour round trip drive but no one has poppet in stock I haven’t pulled poppet yet what should I look for when it’s pulled? And if is bad anything I can do to link it till I get home and can order a new one 2 days left of vacation I don’t want to do anything that will disable the boat

[McQuaig]

If it were me, I'd go ahead and replace the thermostats since you have them now. Put the old ones in hot enough water to check them. If one or both are bad, then your problem should be solved....hopefully enjoy your last days of holiday. You could change the poppet another time. But if the old stats test ok in hot water, you still have a problem, but have at least eliminated one thing. You could check the poppet also, and maybe free it up if it's stuck open, but you'd probably tear the old gasket when removing it.

[DennisJensen]

Installed thermostats and installed water pressure gauge still gets hot and pressure is all over place will get up to 15 psi the drop to almost 0 climb back up then drop back down again then want to stay way down it doesn’t matter what rpms I couldn’t keep constant reading

[McQuaig]

Most likely now the poppit valve? It's simple, just a valve and spring. If you take it out just be sure it goes back in the correct way so it seats properly (could whoever did your new water pump have had it out maybe and put in backwards?). If could have debris or buildup not letting it seat properly, worn spring.....I'm only guessing. Hope I'm not leading you down the wrong path, but stats and valve are the simplest to check, assuming your water pump was done correctly.

[McQuaig]

Most likely now the poppit valve? It's simple, just a grommet, valve and spring. If you take it out just be sure it goes back in the correct way so it seats properly (could whoever did your new water pump have had it out maybe and put in backwards?). If could have debris or buildup not letting it seat properly, weak spring.....I'm only guessing. Hope I'm not leading you down the wrong path, but stats and valve are the simplest to check, assuming your water pump was done correctly.

[DennisJensen]

Well I give up I pulled poppet cleaned it. It wasn’t very dirty. My water pressure was ok for awhile but not right seemed low only about 5 psi at high idle when up on plane around 15 then it would just drop to zero I’m at a loss. I called the shop that did the lower unit they said it was reman so they don’t know if impeller was installed correctly. The strong telltail just has me confused if it was weak I would bet impeller was problem. I did pull the thermostats and started it water is making it to them. And when the temp alarm went off I pulled cowling off I could touch the heads they where hot but not that hot. Thanks McQuaig for all the help

[McQuaig]

That's too bad, sorry couldn't help you. 5 lbs at idle is actually fine for a Yamaha, since they work on volume, not pressure. The only reason I can think of that it would go to 15 lbs and drop to nothing would be the poppit releasing pressure, (possibly the spring doesn't have enough tension left to hold the pressure). I have heard of guys stretching the spring successfully, but that's not the real solution. You may want to send a PM to YAMII on this forum as he seems to know a lot about Vmax's.

[DennisJensen]

Where does the water go that escapes past the poppet valve?

[BuzzB8]

Just throwing out a couple more ideas.

Could the water jacket have enough loose bolts that water is escaping down the back, outside of the engine? How about the gasket between the power head and mid section. I know of a couple 250 OX66 that had these problems.

[DennisJensen]

Everything under the cowling is dry

[javelin90]

Has the boat been stored outside or in a garage? Check the fins on the bottom of the lower unit and make sure something like dirt dobbers have not made a nest inside of the plastic fins. Did a shop replace the impeller? Was the rubber impeller replaced or was an entire water pump kit installed? Plastic housing, stainless water pump plate, new gasket, woodruf key locking rubber impeller in place, check the rubber o-ring where the metal tube slides into the bottom of the powerhead? Sounds like the water pump is your issue and at idle it is ok. Under load the water is bypassing the kit and allowing water pressure to escape and not being pushed up into the powerhead. alot of things can be tied to the water pump, rubber impeller installed backwards, rubber impeller fins not all in the same angle/direction, gap where impeller slides down onto the woodruf key and a small gap not sealing. Are you able to remove the lower unit at the Cabin? If you are I am sending you my number so you can text me pictures to help diagnose issue from afar.

[DennisJensen]

Looks like I have more than normal water coming out from the exhaust just below the cowling when at idle. Maybe weak spring on poppet valve?