Intermittent idle issue

Hi.

2005 VP 4.3gxi in a FW 18 footer
Just got the boat back from marina for tune-up and u-joints. Ran fine the 1st day after small test drive.

New problem the next day.
When at low idle (just up from minimum idle, 5 or 6mph or so) and putzing through the no-wake zones the engine will momentarily go off, just for a split second. It triggers the 2 beep startup and sometimes idles back to where it was or sometimes a bit faster. Happens when cold or hot. Gauges say oil pressure and temp are fine. Sometimes it happens 3 times in a minute and sometimes it wont happen for 3 or 5 minutes.

A couple times it would diesel (like the old 80s cars) until I turn off the key and re-start it.

No problems at high idle (above 10mph or so) or at high speed. Do not notice any running issues otherwise.

Anyone have an idea of what I can check?

New problem AFTER dealer work ? They should find what they caused to be intermittent.

While I am still learning about the electronic side of these ECM controlled motors (I have a 2005 5.0 GXi-E) the 2 beep symptom leads me to think its electrical. Here is my hypothesis: at that particular RPM the motor / boat is vibrating more than at other PRMs and an electrical connection is breaking and remaking. Could be something got knocked loose or not reconnected properly during the maintenance. Or could be something as simple as the key switch and is coincidental happening post maintenance. Have you noticed the gauges dropping out when the engine dies (like the key is turned off)? If yes, suspect key switch or the engine harness to helm connector.

Here are some checks to do. If anyone of these results in the motor dying momentarily, that is the primary suspect. With the motor idling (and not underway), (1) jiggle your keys, (2) looking up under your helm station, gently move around the various wires / wiring harnesses (3) in the engine compt. find the large round connector to the helm and jiggle that (4) jiggle other wires to the dist. and alt.

If no joy on above, post the extent of the maintenance (what was changed) along with any relevant history of boat and engine serial no. Lots of good folks here can help you figure this out.