40 hp missing at 2000rpms

I have a 40 hp 1985 2stroke and rev it up to 2000 rpm and it sounds like it hits a rev limiter. all the fuel delivery system has been redone im thinking its electrical but i dont know where to begin any ideas? my boat dealer didnt even want to look at it he said it was to complicated I need some help

[boats.net]

The overheat or low oil level warning may be engaging and engine will be limited to 2000 rpm's.

how do i check the low oil or over heating warning theres no buzzers sounds. where do i check the over heating is it just a sensor that could be faulty?

[99yam40]

unplug the wires to the temp sencer and short together while switch is on. this should cause the alarm to sound

I looked every where for this sensor cant find it, were is it located 1985 40hp yamaha

ok i touched the wires togerther on the over heat sensor and there was no alarm do i have to replace it?

[jb123]

aparently your buzzer is broken also, as you didnt hear it, right?

thats right no buzzer will it run properly if i disconnect it ?

[jb123]

no you should get it working.

[99yam40]

If the buzzer is not working then you may have a bad sensor giving a false signal that you could not tell was happening causing the RPM limiter

[mechmagcn]

I hate to revive an old thread, but this sounds exactly like my 1988 40LG. It runs fine up to a certain point, say half throttle, then it starts dropping one cylinder, intermitantly. If throttled farther, it will drop out completely. If run at WOT it will try to drop to 1 cylinder at times. I noticed that the warning light will flicker occasionally,but didn't realize that it could cause the firing problems. Can the warning system be disabled temporarily just for test purposes? If so, what wires need to be disconnected?