1983 Merc 115 sudden power loss

[humidex]

1983 Merc 115 outboard "tower of power" She was running fine for about 30 min. Was cruising at 3500rpm when she started sputtering and slowed down. I let off the throttle and suspected I ran out of gas since I was getting NEAR the end of the tank. So I switched to my second tank and went to take off and I could put it full throttle and it had no power. It surged every few seconds like it wants to go but doesn't seem to be getting gas. It idles fine and starts in half a second when warm.

Troubleshooting:
Switched back to first tank. No change
Checked all plug wires and connections. Pulled each plug as it was running and each one had spark and there was a loss of power after each was pulled. Changed all spark plugs. No change
Emptied all carb bowls and refilled. No change
Checked fuel "filter" screen at fuel pump. Wasn't clogged that I could see.
I took it back out and it idles fine but at full throttle it doesn't go anywhere, it seems to be misfiring a bit.
The water cooling stream out of the motor is interrupted as it misfires or stutters. Gets worse at full throttle.

I'm thinking, fuel pump? Carbs suddenly got clogged with a slug of oil possibly? Any ideas??

serial number: 7200742

 

[humidex]

If I sprayed gas into the carbs when I have it full throttle and it takes off, that surely would indicated a gas delivery issue?

 

[wired247]

You may have some partially clogged jets. Those carbs go directly from idle to mains and need a fat idle mix to transition. Try opening up the idle screws a bit.

 

[humidex]

would that happen suddenly? I will try and adjust the idle jets tonight but it seems like it only happens under load. At home with the muffs on in the driveway, it revs up fine

 

[cheers731]

Hi, I have an 86 115HP 2 strokes. Had experienced the same thing yesterday. I ordered a Seloc repair manual today but will appreciate if anyone can tell me or show a pic where the idle jets adjustment screw located?

 

[M0nhegaN]

What I have heard is: if you have spark at and and "idle" but no power much beyond idle, check the stator. My recollection is that the stator has a low speed and a high speed output for the ignition. If the high speed is out of commission you can start the motor and idle along but can't accelerate.

FYI in case you do have to replace with a new stator, I have seen the CDI Electronics stators to be interesting because - at least on the "high performance model" they don't put a whole lot of potting material on the coils and so they have a chance to run a little cooler--- maybe last longer.

I suppose this goes along with the adage that says: "most carburetor problems are electrical".