Keep getting overheat buzzer when idleing for a while.
Have replaced thermostats, but still- buzzer.
Is there a heat sensor that might cause this?
If we accelerate, the buzzer shortly stops.
Probably a stuck poppet.
What are the symptoms of a stuck open poppet valve on a 150 Pro XS?
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Answered in 14 minutes by:
10/23/2013
Marine Mechanic: Jeff G.
Welcome, this question may need more than a single answer. Please post back with additional questions on this at any time.
There are a couple of symptoms. But first let’s look at what it does.
At idle and slow speeds the cooling system is regulated by the thermostats. They open and close to restrict the water in the cylinder heads.
At speed as the engine needs additional cooling the poppet valve comes into effect.
So below 1500 rpm the thermostats control the flow and above 1500 the poppet valve controls the flow.
The water that flows through the poppet valve enters the adapter plate under the engine and then into the midsection. This allows more cooling water to flow through the engine, quiets the exhaust cools the exhaust and helps prevent air from getting into the water pump.
If you have a water pressure gauge you should be able to see the pressure change around the 1500 rpm mark, give or take a few hundred.
Symptoms are overheating at low rpm yet the water pump is pumping properly and the thermostats are open. Additionally, a very long time before the block fills with water and the stream is weak at slow speeds and idle.
When you get going if everything then goes back to “normal” the poppet valve is probably open.
Usually the poppet valve will stay closed from corrosion, broken spring or a hole in the diaphragm which will allow water to exit around the inside of the lower engine cover.
“I am constantly amazed at the stupidity of the general public.”
~my dad
Equipment:
2007 Grady White 222 Fisherman / 250 Yamaha
Simrad NSS evo2 and G4
1- 23 boy that won’t move out)
1 - 19 year old (fishing maniac)
1 - wife (The Warden)
ECFC
When was the last time you put a new water pump in?
why do you claim that it is a false overheat?
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False overheat =no slow to idle or other safety mode. Only happens after idle a while. Goes away if above 1600 rpm.
Waterpump is a yr.
Thermostats 9 months, with new gaskets. Cleaned passages. Worked great for about 3 month.
Suggestions?
DRMajor
quote:
Originally posted by chris Vwhy do you claim that it is a false overheat?
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Just curious Chris, but are there not levels of alarms? May actually be overheating but not to an extent to warrant engine derate? 
Personally drmajor, I’d recommend getting a thermal heat gun and actually know what your engine temp is when alarm goes off.
Mine did the same thing when the water pump was bad. Would overheat at idle and when I got on plane I guess the water would force itself through the engine enough to keep it cool. Could be the poppet valve thing going on above.
something else is going on.
Yamaha alarm system is linked to a pink wire in the harness.
that pink wire has power all the time, and it is searching for a ground.
when anything that makes the buzzer sound activates, it gives the pink wire a ground.
that ground also transfers to the computer, and is designed to put the motor in RPM reduction.
to my knowledge, Yamaha does not have a solid consistent alarm that does not put the engine into RPM reduction.
Only possibility might be if you have an HPDI motor
I notice you said "z"max
did you mean "v"max that is an HPDI which would be a VZ150
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Correct - VMax 150.
Alarm only comes on after idling a while. If I kill the motor and sit a while. It’s OK.
If I gun it above about 1600 RPM, it will go and shortly alarm will stop.
It was fine for about 3-4 months after new thermostats.
DRMajor
look on the side plate that has the model number
is it a VZ150
OR A VX150
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IF I RESPOND IN ALL CAPS, ITS NOT ON PURPOSE, AND I AM NOT YELLING
I found a sandbar and ingested a lot of sand, apparently. My alarm suddenly started sounding while idling at Y-73. It went away under power.
replaced the water pump and it still happened (I had forgotten to reinstall a little plastic bushing). Shope fixed the bushing and replaced the thermostats and it’s run great.
“I am constantly amazed at the stupidity of the general public.”
~my dad
Equipment:
2007 Grady White 222 Fisherman / 250 Yamaha
Simrad NSS evo2 and G4
1- 23 boy that won’t move out)
1 - 19 year old (fishing maniac)
1 - wife (The Warden)
ECFC
Probably need to give the water pump a look…or replace.
DRMajor
quote:
Originally posted by drmajorProbably need to give the water pump a look…or replace.
DRMajor
The alarm is less of a concern to me than the lack of RPM reduction.
if that motor is indeed overheating, you have a bigger problem if the motor isn’t going into guardian mode. easy way to tell if its pumping correctly, is take out the thermostat, and crank it up on the earmuffs. at idle water should quickly fill and spill out of the thermostat hole. if not, the water is not making it to the top of the motor.
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www.bombislandboats.com
IF I RESPOND IN ALL CAPS, ITS NOT ON PURPOSE, AND I AM NOT YELLING
CHRIS
The ZMax is a PX150TLRX.
DRMajor
THAT IS AN 0x66 MOTOR
1999
pretty basic technology.
I am not aware of anything on that motor that would allow an alarm without RPM reduction.
before you do anything, you need to verify that the motor is actually getting hot.
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IF I RESPOND IN ALL CAPS, ITS NOT ON PURPOSE, AND I AM NOT YELLING
Pardon my ignorance—How do you check if the motor is hot?
It has a good Pee stream, but that just verifies the water pump…?
Thanks.
DRMajor
quote:
Originally posted by drmajorPardon my ignorance—How do you check if the motor is hot?
It has a good Pee stream, but that just verifies the water pump…?Thanks.
DRMajor
Get an infrared temp gun. My first one cost me $600+, but you can get them super cheap now a days. Well worth having one. They work great for frying food and just goofing off with checking the temp on everything!
I’m not familiar with that engine, but I have installed several electric temp gauges on outboards just because I like to know. First you have to find a port and correct pipe thread to install the probe, then run one signal wire from it to your gauge, power the gauge and there you go. I don’t like one to get hotter than 150*. That could have changed with modern engines:question:
“live and let live” … “those that deserve it.”
The way this behaves, I wonder about temp sensor. Have to find some info and specs to test. Wonder where it is
DRMajor
BEFORE TRYING TO REPAIR A PROBLEM THAT MAY OR MAY NOT EXIST, IT MAKES A LOT MORE SENSE TO VERIFY YOU ACTUALLY HAVE A PROBLEM OR NOT.
WHEN THE ALARM SOUNDS, USE A LASER THERMOMETER, AND TAKE SIT TEMP. IF ITS 180 DEGREES OR HIGHER, THAT IS TEMP THAT THE ALARM IS DESIGNED TO ACTIVATE AT.
IF THE TEMP IS AROUND 140 THAT IS NORMAL OPERATING TEMP. IF THE ALARM IS SOUNDING AT THAT TMP, YOU ARE EXPEREINCING A FALSE OVERHEAT.
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www.bombislandboats.com
IF I RESPOND IN ALL CAPS, ITS NOT ON PURPOSE, AND I AM NOT YELLING