[abillmann]

Hi all,

I've been enjoying my new (well, new to me!) Mariah 1991 1900ZS for a few weeks, and noticed something with the water temperature gauge.

The gauge ranges from 110 degrees on the left to 170 degrees on the right. Most of the time, at no-wake speeds or slightly faster, it sits pretty steady at about 140. Last night, I had the boat at about 80% of wide open for about three miles and the gauge shot up to just under 170 degrees. After backing off, it came back down to the 140 range within about five minutes.

Is this normal? I mean, I would expect the water temp to increase when the engine is running hard for a few miles. Then again, if it's not supposed to do that (or not supposed to increase that much) I don't want to damage the engine.

Any thoughts, insights or opinions GREATLY appreciated.

[ShabahZ280]

Hmm, my temp gauge shows from 100-250, and always hangs around the 175 mark. Not sure about the early model motors what their normal operating temp is. It would seem normal, but you might want to have your impeller checked, just to be on the safe side. They recommend changing them every 3yrs in freshwater, and every 2yrs in saltwater. It's an overlooked part most of the time, but if yours is damaged, it'll cause the motor to overheat really quickly. Any Mercruiser shop should be able to handle the repair for you, or if you're mechanically inclined, you can do it yourself for about $25 in parts.

[WetWilly]

Hi abillmann,

ShabahZ250 is correct, if you're not sure of the age of the impeller, replace it and you might want to check the thermostat too, it can produce similar symptoms if it's only partially opening.

Good luck and let us know what you find out!