2020 Mercury 150L 4S 6 Beeps at various RPMs

[Keithh41]

Bought my 2020 Ranger tritoon this spring used, test drove with no problems, boat was in great condition. 2nd time on my home lake was slowly speeding up and at 2800 RPMs motor went to what I suspect is called limp mode and I heard 6 beeps. Moving the throttle to neutral seemed to reset and as long as I kept below the 2800 RPMs it ran fine. I Immediately called the local authorized mechanic and scheduled it in. They changed the impeller and flushed the cooling system and $468 latter still got the 6 beeps, only this time beeps didn't sound until 3800 RPMs. When I called back they told me that the engine did not show any codes and they would have to contact mercury, which is the last I've heard from them. I have scowered the forums and talked with local small time repair shops with no luck. After a several more trips on the lake when gas got low I fuel up with some premium gas and added some SeaFoam hoping it was a fuel problem, but no such luck. Still searching for answers and assistance each trip on the lake I would always rev up the motor montoring the RPMs, our trip out about two weeks ago it got all the way up to 4800 RPMs before the beeps came. On our last trip this Mememorial Day the beeps were back this time at 4600 RPMs. On the internet Mercury says it's 1 of 3 sensors, but witch one. Been thinking of investing in a Smarcraft, not certian of the $250 investment. Getting down to the last straw and thinking I'm going to try another mechanic, but thought I give this one last shot. Any information or thoughts would be appreciated.