Yahama 70 hp 2-stroke occasional alarm

[bessie2]

I've searched the forums, and can't find an exact duplicate of my question.

I have a 1999 70 HP 2-cycle Yamaha motor on a Carolina skiff. Once last season, and then just yesterday, I had trouble with the alarm going off. Last season it went off once when I had a full boatload of people. After sitting for a while, it ran again with the same number of people and no problem. In between seasons I had it serviced, water pump changed, etc.

Yesterday while puttering out from the ramp through low water, it went off again. After an hour, it would allow us to run about 25-40 minutes continuously and no problems. Today it did fine, but when we came to shore, it went on again.

Stream of water is coming out of the engine as it should, but the engine would not run at high rpm when the alarm sounds. Seems to run fine at low rpm even with alarm.

We don't want to run it far away from shore in case the alarm sounds again. Looking at a busy 4th with fun on the water. What do you all think?

[99yam40]

Thermostat or PRV may be sticking but who really knows what is going on until you test things and see what is bringing in the alarm.
Could be that you picked up something that covered water pick up.

Do you have gauges that will tell you what the alarm is?
If not I would be inspecting/testing/replacing stats and PRV if you have one and checking on the oil system