2012 Axis A22 - Temp running hotter than it used to - Help?

[Boatdude70]

Up to now:  My boat typically runs between 160 and 170 when we are out on the water.  At times, drops in the 150's, and once in a great great while may hit low 170''s, and immediately comes back down.  This is my baseline.

I recently ruptured a hose (between the thermostat and starboard side exhaust / cat).  It was spraying water, so I shut it down, and got towed in.  I replaced that hose, and decided to replace the impeller at the same time.

Now :  The boat heats up to 160 and (for 2 or 3 temperature cycles) appears to run like it used to.  After about 10 min, it will then climb past 170, and into the 180's before it cools back down to 160.  It then does this pattern fairly regularly (which seems to be new).  So it seems like  the (new) normal range of operation is from 160-185 (about 25 degree swings) where it used to be 160-170 (about 10 degree swings).  And with me seeing the temp run in the 170's and 180's that is freaking me out.  I am pretty sure that when the temp gets to the low 180's if I were to put the boat in idle instead of keeping the rpms up, it would climb even higher before it comes back down.

So far I have checked:  (trans cooler - nothing blocking it, replaced thermostat - no change, took hose off of at input to thermostat and started up the boat (seems like plenty of water coming out). 

Anyone have this problem before?  if so, what did you find?  (Air leak? / Blockage? / Other)?

 

[06malibu]

Try changing the impeller to the old or new. You changed 2 things at once and got new results, start from the beginning to narrow down possible causes

[justgary]

I suspect you have an air leak.  It would have to be on the suction side of the pump, so if the only thing you did was change the impeller, pull the cover plate and check the gasket.

[Saltydog]

Check the thermostat if not already replaced. They start getting lazy before they fail completely. 

[Boatdude70]

Thanks for the suggestions here guys!!

Switching back to the old impeller - I kept the old one, and it actually looks completely brand new, so that may not be a  bad idea.  Busy weekend, did not get to this, but would be a good way of narrowing in on things.

Air Leak - This is my current theory.  Again.. just ran out of time this weekend to look further.

Thermostat - Already changed.  Did not make a difference.

I ended up taking it to the dealer yesterday, as I just don't have time to sort this out myself right now.  I will let you know later what I find out.