Warning system alert at 5300rpm on both Yamaha F100 4 stroke from2001

[pauliris]

I have in France 2 Yamaha F100 on a fishing boat length 23' beam 9' weight 4400lbs propellers 13x19.Both engines have run about 270 hours since 2004.The engines run great up to 4800rpm during hours when the boat is cruising .If I run at 5300rpm the alarm buzzer sounds and the ECU reduced the 2 engines speed but I see no visual indications on the instruments (oil and température).I reduce the throttle to the idle position without stopping the engines , and if I return to 4800rpm immediately the engines run great again .If I run one engine to 5300 rpm and left the other at 4800rpm the buzzer sounds and the ECU reduce the speed, if I change with the other engine the same think occurs. If I try without coupling the engines, both run at 6000rpm without problem. The engines temperatures looks normal.
According to Yamaha service and yamaha shop manuel the buzzer sounds if a low pressure or engine overheating occurs.
I test the 2 oil pressure switch with a pressure gauge , a vacuum pressure pomp , and a multimeter and they are OK (no continuity at 22psi),I test the both temperature sensors and the resistances are normal according the specifications but I decide to change the temperature sensors ,and thermostats on the 2 engines. One Yamaha technicien saw nothing anormal but founded that one rectifier regulator was out of order (problem well known on the engines from 2001) I change both rectifier with the new model, and the charging system is in order (14,92V at 1500 or 3000rpm) and always the same problem at 5300 rpm
New oil, filter, batteries...Yamaha France have never seen such a problem....
Is it possible that the problem comes from the throttle position sensors (on both engines ?) it seems that the ECU read an overspeed of the engine at 5300rpm but only when the boat is cruising (on both engines ?) the 2 ECU are out of order ???
The boat is equipped with the 704 remote control.
Any suggestions would be greatly appreciated
Thanks in advance PAUL

[rodbolt17]

the TPS sensors do not feed any engine speed data to the ECU. only throttle angle.

the overrev limiter wont set an alarm.

now it is possible that a wire has chafed or the DES switch on the back side of the ign key assy may be failing.

the way the DES works is if one engine alarms and goes into RPM reduction it forces the other into RPM reduction as well.

[pauliris]

Warning system alert at 5300rpm on both Yamaha F100 4 strokes from2001

Great thanks Robolt for the reply and explanation.
I will check the DES switch next week and give you the result
Thanks again

[pauliris]

Warning system alert at 5300rpm on both Yamaha F100 4 stroke from2001

Hi, Rodbolt
I checked the DES switch ,the wire and connexion and everything looks fine.
I have the feeling that the problem comes from the 704 remote control box (standard)because in gear, when I want to go to 5300 RPM I need to push the control lever very hard , I feel the throttle cable has a very high tension ant it seems that something is happening in the box at this speed .In free accelerator position I go to 6000RPM easily . Maybe I have to readjust the cable in the engine but coming out from the 704 control box I see the power trim wire left and right and both switches and the wire for neutral safety switches located in the box but there are another 2 wire harness, with 4 wires each, going to the DES switch and I ask me the fonction and if something can be wrong in the box with this connexion (safety or stop system or a wire harness pinch..??)
Do you know where I can buy the Yamaha manual for the remote control box
Thank you in advance for you help

[rodbolt17]

quit chasing that ghost.
there is nothing in a 704 box that can cause any alarms.

why rev a motor with no load?
teat on a boar hog and a good way to destroy a motor.