2003 optimax 200 over heat alarm only over 4200 rpm

[hawkf250]

Ok I'm at my wits end on this one... Hope you guys can help I have a 200 optimax with an m2 jet drive. Anytime I go over 4200 rpm the lights not the gauges slightly dim and I get an overheat or steady alarm tone.
If I back it. Down below 4200 the lights brighten back up and the tone immediately goes away. I have checked and have good water flow and the powerhead is not overheating. I have reverse flushed and checked all the lines for clogs but All seems well. If I go to wide open throttle the alarm will immediately sound then rpms will drop to 5500 on it's own but anything under WOT the engine does not go into limp mode. Any ideas?

 

[Texasmark]

What's confusing here is the dimming of the lights. No correlation between the two symptoms other than a short in the wiring harness in the control box. It has to be in the control box as you have to get ground (batt -) on the low side of the horn to get it to sound. The lights could be dimming because whatever is shorting out the horn to make it blow is also shorting out your lights. I'd associate the 4200 rpm and immediate recovery a throttle position of the shift/throttle lever in the control box that does the shorting.

Some control boxes have the horn in the box and others have it tied onto the wiring harness adjacent to the control box. You didn't say if you had the Commander 2000, 3000 or something else and it depends on who built the boat as to where they installed the horn. If the horn is attached to the wiring harness, external to the control box then I don't know where you'd find + and - shorting out at 4200 rpm and getting the - down stream of the horn.

 

[hawkf250]

I thought that as well but this is a flush mount control box with no wires going to or near it... All engine wording including the horn are routed well away from the control box and cables. And go to the dash. Crazy huh?

 

[Texasmark]

I thought that as well but this is a flush mount control box with no wires going to or near it... All engine wording including the horn are routed well away from the control box and cables. And go to the dash. Crazy huh?

Have a big black plastic button at the pivot point of the shift/throttle lever? That would be the 3000 Merc/Quicksilver series. All the stuff is behind the bulkhead to which it's mounted.

".............. All engine wording including the horn................." Don't understand that. Some engine information is displayed on the dash in addition to what goes to the control: Sometimes a visual alarm indicator (light bulb) is on the dash, the horn button could be on the dash plus switches for bilge pump, trim might be there if not on the handle of the throttle/shift control.......you still have to have the mechanical cables between the control box and the engine to operate it along with the electrical connections that are needed to operate the engine.

 

[hawkf250]

The engine "wires" not wording... Sorry my phone has an autocorrect issue lol. But no this is not a classic or 3000 control box this is a jet drive boat so No wiring at all going to the control box no trim or tillt and the nuetral switch is on the motor. I'm reasonably sure that all associated wiring is good and the fact that the motor goes into limp mode rules out an after ecu short to ground.

 

[Texasmark]

Looks like you are out of my league. Sorry.