Overheating alarm goes off sometimes and boat sputters

[wylielandon]

I have a 2012 StarCraft 220 scx with a Mercruiser 350 Mag. I changed out the water pump impeller, had all the codes cleared. Now the boat at idle will keep a temp of 160. Once I take off the and get to a good cruising speed, the temperature gauge drops to zero and the alarm goes off making my boat sputter. I can shift to neutral and take right back off full throttle no problem. 2-3 mins later same thing. I have had it hooked back up to a code reader, and there were not any codes. Any thoughts or ideas.

 

[alldodge]

temperature gauge drops to zero and the alarm goes off making my boat sputter

Howdy

Your motor has two sensors in the thermostat housing, temp gauge sender and engine temp sender. The engine temp sender goes to the PCM and set off the alarm. The puzzler is saying the gauge goes to zero (cold). If it went off and temp stayed the same I would look at the water pressure switch.

Get a IR temp gun and when it goes off, check the temp at the thermostat housing.