Offshoreonly.com - 496 Mag Warning Horn

I have a 2002 Baja with a 496 Mag that has been giving me a warning horn for about the last week. When the boat is running I get the 2 horns/minute warning. The boat will run good until I get up around 4300 to 4500rpm and then I get a constant horn until I get off of plane and slowed down at which time the horn goes away. I can take off again it will do the same thing. Since I am not sure if the two warnings go together I tried to install a new gear lube reservoir but it did not change anything. When running the water temperature is good at 165 to 170F, the oil pressure is between 40 and 50 psi on the gauge and the voltage is around 13.5v. The first time it did this I took it to the shop and it appeared to show a low oil pressure for 5 sec along with numerous other codes that I was thinking may have been from me unhooking sensors. We cleared the codes and I took it back out but I haven’t got the results from hooking it back up to the computer. Any ideas????