Muff Flushing Mystery - Any Ideas?

[HMBJack]

I did the water backflush up through the black TT hose and had no effect. I could hear the water filling the powerhead and backflushing but nothing changed.

Thanks for the suggestion pstephens but for now, I will not pull the LU off again. I kinda give up now on this.

To summarize - two identical F250's:
With good water pressure at my dock, they both used to pee on the garden hose fitting (engine off) as well as on muffs + garden hose with engine ON.
My Port motor, had an over heat alarm the other day at 4,300 RPM's and I immediately shut it down.
I think I had a kelp leaf over my lower unit intake as this has happened before. Anyway, the engine started right up and behaved normal - TT pee stream at low and high RPM's.

As a precaution, I pulled the LU and inspected and replaced the impeller (old one was fine).
I then removed and inspected the poppet - it was perfect.
I then removed the TT hose and backflushed the powerhead with water thinking something was blocking it. No love...
T-stats were changed six months ago.

So no pee stream from the TT in freshwater flush mode (engine on or off) yet a good pee stream with the boat in the water.

This "Muff Mystery" really has me baffled! I now however give up unless you can think of something else.

Thank you for your thoughts and suggestions. I really appreciate it!

[DennisG01]

I know you said you checked the impeller, but...

If you had an overheat alarm, it's reasonable to think that the impeller may have been compromised (maybe not as "flexible" as it used to be) or the housing/wear plates now have a small groove in them). It doesn't take much - if you can get a fingernail even just slightly caught in a groove, that is often enough.

[99yam40]

I always do the kit.
that gets the wear plate and cup too

[walleye1]

If you got it hot you may need the plastic housing that holds the the ss cup.

[HMBJack]

Good ideas but I had a whole new water pump kit installed exactly one year ago.
Upon my inspection a couple of days ago, everything looked perfect in there including the plastic housing (which I focused heavily on for obvious reasons).
I put in a new impeller anyway. The thing pees like a race horse in the salt. Just nothing when flushing... Weird.

[HMBJack]

I solved the above mystery today (no pee stream while on muffs but pees when in salt water).

And the answer is...

>>> One of my two Thermostats was in the stuck OPEN position.

After I installed new T-stats, it now pees like a race horse both in salt AND on the muffs or garden hose fitting.

Not enough pressure from the FW with that T-stat open I guess.