Alarm noise on merc 2.5 EFI 280 HP

[Kanookstr]

I have twin merc 2001 2.5 EFI sports 280HP. i have one that started making a continuous alarm noise after running for 5 min or so around 4500 and higher rpm. i would back off to an idle and it would stop. i thought it might be temp but i pulled off the cowl cover and the heads felt fine. i even checked the other engine and it felt the same.
Today i replaced the impeller just in case and it did the same thing, i did notice that even when the alarm is going on i can still run the engine at any rpm including WOT. I was told that if it were high water temp that the ECU would limit my rpms to below 5000 rpm. but i can reach 7000 even when the alarm is on??? any sugestions would be very helpfull.
thanks

[FWP3LCF]

water psi ?????

[Kanookstr]

i put a new impeller and i still have the same problem. The water coming out the other engine has the same amount as the one giving me the buzzer alarm

[olmo40]

If the motor still revs it may be a faulty sensor ? try swapping them or disconnscting the one making the noise,if you are sure temp is ok .A fuel restriction can set the alarm off but usually limit the rpm also ,Empty your water seperator into a container and look for debris or little black particles which can be the fuel line deteriating .How long since the injectors have has a service ?

[Kanookstr]

i put new water seps and inline filters this year before going out for the first time. I even emptied all the gas from the tank and put new 93 octain fuel. i lost a power head one year because of bad gas so i start with fresh fuel every season. i didnt know these engines had a fuel alarm as well? if they do i can check fuel pressure as well this weekend. just trying to get as much info as possible before going up to the river this weekend.

[olmo40]

They dont have a fuel alarm , a fuel restriction will make the motor run hotter and hence can set off the over heat alarm .

[skydog]

Hook up DDT look for fault codes.