Single beep when RPMs under 2000

[05StingRay]

Good afternoon all

Struggling with an issue on my 05 4.3 MPI. Runs great when engine is running hard, the issue only comes when idling or running at RPMs under 2000. We will be putting along and get a single beep and immediate cut back on power, can then rev the engine back up and acts like nothing happened. Keep putting along and it will do it again but not at any regular interval. Get through the no wake zone that we were putting through and hammer down and no problem running at normal top speed or continuing across the water until we get back to the lower RPM.
Gauges all read fine for water temp and oil pressure. Checked oil level and it was fine, checked drive lube and it was good. Really confused as to what is causing my issue but look forward to any advice you may have!

 

[alldodge]

Watch your voltage reading, might be dropping below 14V

 

[05StingRay]

What is the best way to test that?

 

[alldodge]

Watch your battery gauge at the helm. If you don't have one, connect one at the 50 amp breaker on the motor or purple wire at the key switch

 

[QBhoy]

I’d just double check the temp she is running at when going slow. What you are saying has all the signs of a bad impeller on its way out.

 

[05StingRay]

Took it to a new mechanic this week and he replaced the thermostat because he said it wasn’t coming up to temp. Got that done now says the codes show the tps and iac. Is either of those a reasonable explanation for the alarm I am getting?

 

[alldodge]

Paraphrase: after replacing the thermostat it NOW has codes

This is kind of a bad start from my view. I'm thinking it either had codes before the thermostat change, or he's guessing. Would be nice to know (better yet see) what codes are seen

The TPS and IAC run off of 12V source
If voltage is dropping both can throw a code

Below is a list of 555 codes and none are a single beep. They are either continuous or 2 beeps. This is the reason I think this might be electrical. Power drops, alarm sounds and ECM cuts power which turns off alarm and it comes back. Might be a bad connection

 

[05StingRay]

Alldodge, I agree that it seems like he is guessing. I am going to go pick it up tomorrow and see what I can figure out with the voltage and go from there. I know I can do the TPS and IAC myself it no luck with the voltage.

 

[05StingRay]

UPDATE
Checked and cleaned battery connections, checked voltage at 50 amp breaker and it never dropped below 14.3v
Changed IAC and TPS to rule those out and no change.
Frustration was setting in and we started looking at everything we could find. By chance we unplugged the ground to the lube bottle, no beeps. Plugged it back in and more beeps than were before. Never a constant beep just one beep sporadically. Unplugged both leads to the lube bottle and again no beeps for awhile then one beep but no more.
So I am not sure if the lube bottle is actually involved or not. Also not sure if it would make a difference if one of the lube bottle leads was unhooked versus both of them being unhooked.
Tried to get it to a different mechanic but they aren't taking any service appointments until winterizations are done for the year. So I am kind of stuck if I can't get it myself.
Don't really want to buy a scan tool as I am selling the boat. I did see that there is a mobile version of the vessel view, would that give me accurate fault codes to where I could see what is happening?
Any input is much appreciated because I am beyond frustrated.

 

[alldodge]

The lube bottle is a switch with 2 leads. One goes to the ECM and the other goes to ground. If the switch goes bad or the bottle is low it grounds the lead going to the ECM. If lube bottle is disconnected, another switch such as oil pressure can do the same

 

[05StingRay]

Alldodge can’t thank you enough for all your help/knowledge. Sounds like I need to find a good mechanic with a scanner to pinpoint what’s going on. Thanks again