I had a 01 21i and currently have an 03 21i both equiped with the 315 MPI. The Merc owners manual specifies the thermostat to be 160 degrees F yet on both boats the temp gauge will indicate 175 degrees when warmed up. I've been in several other brands of inboard boats equiped with GM motors and they all would run wih a temp of 160 degrees. Just curious if anyone knows why the difference in engine temps.
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don't know why the specs are different....from the actual.
But i can tell you that 170-175 is normal, on all the tige's i've been on that's been the norm.
my only guess would be cooling water temp when they spec'd the motor? -
not sure if you know or not, but the thermostat will not really effect the running temp of your engine (unless it is less than the thermostat rating). The thermostat merley blocks water flow into the engine until the engine reaches the tempurature (in this case 160) and then opens and lets water run into the engine. if the temp goes to 175 or even 200, the thermostat is out of the game after 160 unless it is blocking flow, which although many people try to cool an engine by pulling it, doesn't typically drop your running temp by a degree. sorry if this is all old story for you.Comment
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Blr,
couldn't have said it better myself
DomOriginally posted by G-MONEYComment
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I do agree that the thermostat gives the engine a minimum operating temp and if the temp rises above that then the thermostat should be wide open. I this case I believe the thermostat is still in the loop. The lake water can be 50 degrees or 85 degrees and the gauge on the dash will read the same. I suspect that the sensor for the engine water temp is not right at the thermostat but maybe dowm stream a little so the water temp is slightly higher. I have to look on mine Sunday and see if I can find the sensor.Comment
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at least in most cars, the temp gauge is screwed into the side of the block, not sure it would be any different on a boat??Comment
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Your sensor for your engine temp is in the housing that holds thermostat on a Mercruiser MPI. I just change mine a couple of days ago.Comment
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