Indmar 400 Thermostat

[jcarter20]

Changed the thermostat, checked the idler pulley and the raw water impeller. I thought I had the impeller in backwards at first and changed it around, but that didn’t make a difference either way to be honest. How would you know if the heat exchanger is the problem? Should this hose be hot? It was cold and my engine temp was climbing from 165 to 171 at idle speed on the fake a lake in the driveway. It also seemed like water wasn’t coming out of my exhaust like normal after idling for about 3-4 minutes so I killed the engine. It started out spewing water like always. Any thoughts?
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[jcarter20]

The weird thing is at 2000 rpm’s temp went to 169. I backed it off to idle and it dropped to 165 and then raised all the way up to 171 while remaining at idle. I would have thought it would continue to drop or at least maintain at 165ish.


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[Holdmybeer]

Did it ever go over 171 while idling?

Your heat exchanger could have buildup in it. I would remove the plug and see what comes out of the raw water side. Also, is your coolant low in the overflow tank. When I had to add coolant you had to do it through the small hose with a funnel to get past the air bubble that is created.

[jcarter20]

The level was not low, but I did wonder about air in the system. When you say small hose, is that on the port side of the motor? I have a heater, so rather than the connector loop, I have two hoses coming out and going to the heater pump.


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[Holdmybeer]

I had to use this hose to fill the system and bypass an air bubble.
Disconnect and lift up high, use a funnel to fill until bottom of funnel won't drain (it will only take 1 or 2 ounces at a time). Start the boat and it should suck it down and air will bubble into the bottom of the tank once the thermostat opens.

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