1988 Merc 115 inline 6-Rough in low gear only after WOT

[sklos19]

Hi all,
I Was hoping someone who knew more about these motors could potentially shed some light on an issue I have been having or where to start troubleshooting. Thank you!

Boat: 1988 procraft 1660v with merc 115 inline 6.
Background:
Motor starts up perfectly, most of the time first or second turn of key. The motor also runs perfectly in neutral or low gear all day long when/if the throttle is not engaged more than 50%. The motor also runs like a horse at full throttle and I have no issue. However, once I run WOT for more than a minute or two and try to come off plane back to idle the motor will die. The motor will continue to start perfectly but I will have to rev up in neutral to keep it from dying and it will also die in low rpms if I do not engage a good amount of throttle once in gear. If the boat sits for a few hours/overnight it will once again run perfectly at all amounts of throttle until WOT and then the issue occurs again.

About a year ago the following work was down to motor:
Carbs rebuilt, new hoses, connections, fuel filter, water pump, power packs, and spark plugs. Boat ran perfect until about a month ago.

Appreciate any feedback!

 

[Chris1956]

Tough one...check for exhaust leak under cowling, or simply run it with wrap cowling off.

 

[Faztbullet]

Sounds like a float is sticking and flooding a couple cylinders. Trimming it up and bouncing back home unsticks it and engine runs fine.

 

[racerone]

Running with back drag on carburetors ?----What elevation ?---Might be as simple as opening low speed mixture screws 1/8th turn at a time.

 

[jimmbo]

My 1984 inline 115 didn't have a Low Gear.
I wonder if the Idle Stabilizer was disconnected? I know a lot of People say to unhook it, but Mine never gave any Trouble, even after 14 yrs.
My 115 used to get Stuck Floats quite regularly and would run crappy, but I could also see Fuel dripping out of Air Bleed Orifice/Bowl Vent.