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2005 40 hp stalls at high throttle

S

sdeloach

New member
I have a 2005 2-stroke, 3 cylinder 40 hp mercury outboard. When the throttle is increased to three-quarter speed or higher it immediately dies. It starts and runs at low speed fine. It has a small miss at low speed. I tried different tanks with different lines and ball bulbs. I’ve also changed the fuel filter and gas line in the motor and changed the spark plugs. I’ve taken the screws out of all three carburetor and the screws and carburetor appeared exceptionally clean. I ran a compression test on all three cylinders and all three read the same. I talked with several certified boat mechanics and none of them have heard of this problem or find it in any of the books. Any ideas on what the problem could be?
 
IF your motor has a trigger coil (part under the flywheel moved by the throttle arm) then it does not have alow/ high speed switch box design. If there is no trigger coil, however, then all spark advance is done within the switch box and the high speed portion of it OR the stator is shot.
You can check the stator circuits with a simple volt meter.

Jeff

PS: From what I see in my files, your motor has a trigger coil (and, hence, no high speed switch box set up). You need to check, though, as you might have a foreign built motor that might be different.
 
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Your motor has a moveable trigger, stator and CDM modules. Remove the cowling and install a timing lite to on of the sparkplug leads, run it to problem happens and see if spark drops when this happens, if so disconnect the main harness from engine and retest. If it does not fail you are getting feed back on kill circuit of CDMs from wiring problem in key/kill switch. If it still fails check battery voltage as if low you could have a rectifier overheating stator an causing it to drop out. Finally ohm the stator as I have only seen 7-8 of these fail as pretty dependable on the CDM engines. The miss you have at low speed leads me to to believe you have a CDM module acting up as the share the same kill/ground internallly.
 
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