merc 350 mag temperature variation

[andyj]

I have twin 350 mags in a 27 foot SR pachanga. Port engine, while running fine @ 4000K the temperature gauge gradually swings from 100 - 200 degrees every 15 - 30 seconds or so. exhaust plumes look even - no overheating sirens. At Idle speed it holds true at about 145. Does this sound familiar and is it symptomatic of a thermostat or a sending unit, or loose gauge wires? It does not run hot and stay there, or go too cool and stay there. Always moving up and down at higher RPM.

 

[vipzach]

Re: merc 350 mag temperature variation

Welcome to iboats! I think that swing is way to fast to be a thermostat. I think I would be checking the wiring and electrical connections, maybe even the gauge itself.

 

[andyj]

Re: merc 350 mag temperature variation

Thanks for your input zach - I modified the post a bit.