Water Temperature Gauge Extreme Fluctuation with Throttle

[blugrasmaniac]

Hey, guys and gals...

I've got a boat with a 1994 Evinrude 175HP V6, and as far as I know it has the original water temp gauge.

The question I have is on the behavior of the gauge. It reads basically zero at idle (maybe barely off the lower peg), but moves with the throttle...meaning that at WOT, the gauge reads what appears to be correct - safely inside the red. At half throttle, it's about halfway up, etc.

Is this normal? This behavior seems very odd to me. I heard that the temp should rise at idle, if anything, and drop at higher rpms. Currently, it doesn't reflect the operating temperature of the head. Now maybe the water is clod enough that the water temp at idle doesn't get very hot, I don't know. But the lake water temp has been about 45F.

 

[bob johnson]

Re: Water Temperature Gauge Extreme Fluctuation with Throttle

I have two gauges, the lowest reading is 100 degrees an it goes up to 260derees or so....is your gauge just a hot-cold gauge???

sounds like you are reading water pressure......

bob

 

[oldboat1]

Re: Water Temperature Gauge Extreme Fluctuation with Throttle

lots of good questions and posts here on monitoring cooling/engine temp, from water and pressure gauges to buzzers and tell-tales. I think the old cylinder head gauge might be overlooked a few times when it could be the easiest solution, IMO. I think Teleflex and Faria have versions of these gauges, packaged with sensors. iBoats has a link to a gauge or two, and a source for senders. The easiest way to install is with a clamp that attaches to a head bolt (sensor in contact with the head). These are good redundant systems if uneasy about your current one.

(can't see why it wouldn't work with a minimal amt. of set-up on non-electric engines too, BTW, as long as there is a battery source -- say, for lights, fishfinders, etc. -- some kind of on/off switch in lieu of a keyswitch, and a common ground to the engine block.) Just a thought.

 

[blugrasmaniac]

Re: Water Temperature Gauge Extreme Fluctuation with Throttle

Thanks, both of you. I didn't think about it reading water pressure - that is what it sounds like. I'll look at it. It may just be wired to a pressure sender. I'll see what other ideas are on here for setting up some additional monitoring.

 

[boobie]

Re: Water Temperature Gauge Extreme Fluctuation with Throttle

Look at the back of the gauge and see if there is a hose going to it.

 

[emdsapmgr]

Re: Water Temperature Gauge Extreme Fluctuation with Throttle

You did not mention what the numbers are on the face of the gauge. Maybe it's an old one with just colored areas, green, red, etc. You are correct, usually your outboard will run it's warmest temps at idle. (143-155 degrees.) Once on plane and the stats open up, the powerhead temps will decrease maybe 20 degrees. (Or more-in cold water.) If it's a water pressure gauge, it will idle about 4-6 lbs and could go up to around 20 lbs at WOT. If I had a gauge without any number markings, I'd consider replacing it-with a better gauge.

 

[boobie]

Re: Water Temperature Gauge Extreme Fluctuation with Throttle

Did you ever look behind the gauge ??