2014 Ski Nautique 200 cooling issue

[bobbulfer]

I have a 2014 Ski Nautique 200 5.7 closed coastal edition so it has closed cooling.  I have 1400 hours.  In June we got a warning DTC1415 EMWT1 higher than expected at stage 1.  We found some weeds in the strainer and have not had an issue until this week we got the same warning 4 different times.  However the weeds are gone from the lake now and no weeds are in the strainer.  From what I can tell it is the left side exhaust manifold is getting hot.  
It seems to act up when you let it sit for about 5 minutes between sets and idle back down the course.  I don’t get the warning light until the boat gets up to speed and then goes to limp mode.  If I turn it off and restart the warning goes away until I add throttle for another pass.  If I let it sit with engine cover up for 5 minutes it is fine.

The engine temps stays between 155 and 163 at all times when running.   I just  put a new impeller in it even though the old one looked fine.  I  have never had a blade brake on one.   I borrowed a friends radar heat gun and the left exhaust manifold is about 10 degrees hotter than right side.  Could I have a partial blockage in the left manifold.
 

The original owner had the same issue about a 1000 hours ago and the dealer flashed the ecm to change the warning parameters.

Any ideas of what I can check or where I can take it.  I’m in MN and dreading taking it to marine max the Nautique dealer.

Thanks

[skiep]

Impeller needs to be replaced  Happens to me all the time between two boats

[bobbulfer]

Already put new impeller in and still have the issue.

[Ski_Dad]

Drain the manifolds and see if water comes out both sides.  It might just have crud in the drain. 

[bobbulfer]

The manifolds are all fresh water or antifreeze.  Raw water comes out of heat exchanger and goes out back of manifolds down the exhaust.  

[bobbulfer]

Has anyone replaced a thermostat on a 343 closed cooling before.  It is in the heat exchanger and I’m a little concerned about letting too much air in the system when I open it up.

[paul]

Guaranteed your manifolds are plugged. Pull the bottom drain on each manifold (individually) and run the engine to flush out the particulate. Then flush the raw water cooling system with dilute acid. 

[bobbulfer]

From what I can tell my manifolds are cooled on the closed loop portion.  I loosened bottom plug and antifreeze came out.  The raw water from heat exchanger dumps in back of manifold going down exhaust.  No drain for that portion.

[DW]

Another spot to check with your temp gun is each side of the intake manifold water passage leading in to the tstat housing.  You might find a split across each side, you can also check which side incorporates the water temp and / or alarm sensor.

[Alberto Soares]

Check @Jody_Seal comment