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Temperature problem 50 MPI

R

rick12341

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"My engine has been running a

"My engine has been running a bit hot (185 or so, performance seems fine) when I am running about 4000 RPMs. Roughly for every 2oo RPM increase I see a 3-5 degree increase in temp until I get to about 4600 when I am running too close to 200 and throttle back. It was dropping back down to 160-165 in a few seconds after throttling back.

I had a new impeller put in last year so I am optimistic about it being OK. I put a new T stat in last night and the problem changed, worse in my opinion. Once heated up it stays around 170-175 degrees (up from 160-165 with the old t-stat) and goes up from there. At 4000 RPMs I am running 185-187 and still see the increase in temp as RPMs increase.

The thing I noticed is that when I key off the temp gauge stays right where it was. All of my other engine status gauges peg to the right. Upon cycling the key (not starting the engine), it will either instantly swing down to 160 or not move at all. When it flips to 160, it slowly creeps up to 175-180 over about a minute. If I start the boat, it drops back down to 170.

Could this be a bad gauge or temp sending unit? Any other thoughts?"
 
"This could still be an impell

"This could still be an impeller problem as the RPM's increase those blades really try and stretch out, might be losing some water flow. However your gauge symptoms don't sound right either so go to this link and scroll down, in the middle section you will see a simple test to do on the gauge and then a way to measure the resistance (ohms) of the sender itself at different temps.
http://www.teleflexmarine.com/cgi-bin/frameset2.cgi?site=gauges&type=us&link2=10 47"
 
"The gauge seems to be OK and

"The gauge seems to be OK and so does the sender. I did a little more digging around today, the port exhaust riser gets quite warm,you cant keep your hand on it very long at idle. When I bump up the RPMs it cools down... seems like there is some flow but it its not enough to keep the riser cool. Would this cause the engine to run hot?"
 
"Sure it could, wonder if the

"Sure it could, wonder if the impeller that was changed was all there? There could be a restriction on the port (piece of impeller) side causing the flow problem. You would need to backflush the system and see if that shows anything or helps."
 
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