Constant alarm after sucking up mud. 2004 2 stroke 50 up Yamaha

[Arestheblue]

Ok, here goes. Yesterday I launched my boat and sucked up a bunch of mud to the point the tell-tale got clogged and there was no indication of cooling.
As soon as we got out of the mud, the general, non specific alarm went off, and I turned off the motor. Turned it back on, no alarm. So continued on my way. About 5 minutes later, alarm came on again, so rinse/repeat.
Eventually, the alarm came in and stayed in. Also, the motor would start vibrating excessively until I brought it down below 2000 rpm. I determined that we were unable to return too the original boat launch and ran it intermittently for the next few hours to get to another boat launch.
So far, I replaced the water pump impeller(looked pretty bad) and gave it a fresh water flush, but the only mud I got out was out of the tell-tale. Alarm comes in continuously when I have it turned over. I ordered a new thermostat, and I noticed an electrical connection near the front of the housing was disconnected, right as I was no longer able to work on it.
Also, it starts in gear now, but that was my fault when I replaced the impeller. I'm trying to figure out what could cause the alarm, I assume that is also what is forcing the motor into "safe mode."

 

[99yam40]

I have had some luck with hooking a water hose to the water pipe with lower unit removed, remove the stat, turning water hose on full blast,and injecting compressed air into that water stream right before it enters the water pipe in short blasts.
This seems to help loosen and remove a lot of junk that has settled into the lower parts of the power head.

But it may take opening up the motor to get it all out.

Disconnecting the over temperature alarm switch while the alarm is sounding will tell you if that is what is causing the alarm

 

[ClassicAQ]

Stat alarm is triggered when engine temp elevates above normal operating temp, subsequently grounding the switch and causing alarm to activate. If you were to plug together the 2 engine side stat wires and start the engine, there should be no alarm. If so, you've got bad wiring. If engine side stat wires are plugged into the stat and you unplugged either wire while engine is running, the alarm should active.

Once you've confirmed high temp alarm is functioning properly but are still getting high temp alarm, even though water is exiting the tell tale, this would indicate cooling passage blockage. Follow 99yam suggestion above for clearing out passages. With LU removed you can also do in reverse what 99yam has suggested, by removing the plastic part from the tell tale's rubber hose that inserts into lower cowling. Blast water/compressed air up through the hose. You should see water exit the water pipe. If all else fails, remove cylinder head and head covers to visually inspect cooling passages.

 

[Sea Rider]

If the impeller was destroyed while boating on muddy water, did engine overheated ? if so, retorque head gasket bolts to specs. Asume there's an overheat system that shuts off or lessen revs to safe minimum ?

Happy Boating

 

[99yam40]

Stat alarm is triggered when engine temp elevates above normal operating temp, subsequently grounding the switch and causing alarm to activate. If you were to plug together the 2 engine side stat wires and start the engine, there should be no alarm. If so, you've got bad wiring. If engine side stat wires are plugged into the stat and you unplugged either wire while engine is running, the alarm should active.

You need to look at the wires you are talking about a little closer.
one is a ground.
if you hook them together that would ground the other causing the alarm and RPM reduction

 

[ClassicAQ]

You need to look at the wires you are talking about a little closer.
one is a ground.
if you hook them together that would ground the other causing the alarm and RPM reduction

Now re-reading my post, you're 100% correct. My suggestion, "If you were to plug together the 2 engine side stat wires and start the engine, there should be no alarm." Typing mistake...this should read "there should be an alarm". Obviously 1 of the 2 engine side stat wires is ground, and plugging these 2 together would therefore "ground".

Thanks for catching my error.