What Is this alarm? Mercury 2001 125hp

lgaytan said:

Hi guys getting back to this topic I went out this weekend on the Boat and I confirmed the issue if over heating is only in los RPMs no issue at all while planning but if I stay in low RPMs for five minutes or less the alarm turns on if I then rev up the motor the alarm goes off. So based on what Texasmark said previously the issue should be on the thermostat right? The poppet valve should be working as it it supposed to work on higher RPMs?

Thanks

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I don't know if this got answered and I didn't look through the responses as I am here answering a different question. The Tstat operates up to about 2500 RPM (per the serv. manual) and the Poppet above that when increased flow is required. I don't know if I mentioned it here but in 2004 I bought a used 2002 rig with a Merc 90. On the maiden voyage, I cleared the "no wake" floats and got lazily on plane. Was at a cruising speed for a short while and the alarm sounded. I sped up wondering what to do and what was the problem and in a minute or so, the alarm went off......OK, boated for awhile at the higher speed and decided to go back to the ramp....as soon as I slowed down, bam.....alarm was on again. Changed out the stat, and checked the pop off and that was that.

Based on what I experience I think it's the thermostat, not opening at the temperature required on low RPMs then if REVing up the poppet valve seems to be working good, I will change the thermostat and try again.

Installed a new factory impeller ?

racerone said:

Installed a new factory impeller ?

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I didn't changed, I have the replacement but didn't had time to make the change, I see a good flow through the pee hole, any ways I think I will change it and the thermostat as well.