Should I lean to the idea of my running rich issue being the temp sensor?

fwc =fresh water cooling w/heat exchanger on front of motor if your in fresh water you probably dont have this
the check valves your talking about are most likely for a central drain system for winterizing
on your thermastat housing the largest hose should swing around to water circulating pump the next largest hose should be your water feed, thats the hose i backflush with [goes to p/s cooler]
usually the impellar material will be trapped in the p/s cooler,although i have had it get lodged in the thermastat
i would repair the raw water pump, backflush p/s cooler,hook everything back up and see what u have if it still runs hot or cold pull the t stat to check for material
once it passes that point it shouldnt cause a problem

you really need to address your water issue first
the computer could be going into default mode cause of the high temp once you get the raw water pump corrected see if the rich condition still exists

im sorry you did say that the boat is an 05 there probably is a y fitting in the big hose from the thermastat hsng to the circulating pump your water feed hooks up to the bottom of the y fitting not at the thermastat hsng like earlier models

I already pulled and replaced the thermostat. Had no material in the housing. I fill flush from the p.s. cooler. Thanks for the assistance

O.k....I have a new impeller and thermostat ...installing this week.
thanks

As it was addressed by others, you need to pull ALL the coolant hoses and back flush and clean out for all the impeller debris. I believe there are two coolant temp sensors. One for the gauge on the dash, and the other for the ECM operation.

If the temp sensor for the ECM was bad or not giving information it might be tripping a limp home mode.....or since it reads ECT (engine coolant temp) and uses this parameter to adjust fuel mapping it may be forcing the motor to run needlessly rich based on false information. They typically run richer when cold and it slowly phases out the ECT multiplier as the engine warms up, akin to a choke on a carb motor.

Lastly, and probably the least likely the injectors might be leaking causing the rich idle condition.

Fix the impeller, line debris, drain the block and look for debris there too. Verify the ECT sensor is working and go from there.

Good luck.

Flushed out system. Only one little piece came out. Installing pump this evening.
Thanx

the temp sensors may not be bad, they need to be surrounded by water. not air or steam, it will not recognize the temp, it will instead read cooler. this will tell the ecm engine is cold or choke, warm-up sequence = overfuel. smell oil for gas also. with that extended system drain, it has check valves that you want to ensure are at least flushed to prevent water taking shortcuts out. what is t-stat temp.