2000 airnautique with limp mode issue gt40

[toyfreak]

My buddy has a 2000 nautique with a gt40 motor and he let someone drive it last week and now it has an engine light upon idle and wont rev up seems like a limp mode . Cant tell exactly what rpms because the guage dosnt work but it can tow a tube at little kids speed and if try to go faster it cuts out. Temperature is at 160 165 and everything else seems perfect. What sensors make the engine light trip? We tested the front temp sensor and it seems to be working correctly when we grounded it out. Any help would be appreciated tests we can do etc.

Thanks
Ryan