'76 Johnson 70hp worked perfect/now stalls wont idle in water

[voltron]

Thanks ahead for any help..
Got a '76 Johnson 70hp w/ a 12 gal tank. Worked perfect @ begining of the year..now won't idle in water, sounds like it wants to stay idling but stalls immediately. Put muffs on, started right up, idled fine, turn up throttle, looked great..except too much smoke I was told. Took out spark plugs, oil on tips. Replaced spark plugs.Drained gas/oil out of tank..put in 1qt oil 12gallons of gas and 1oz sta-bil. Same result. The spark plug wires and what they connect into are brand new too. Any ideas?? Thanks again

[DJ]

1. Champion Plugs-Only.

2. Your carburetors are plugged. a GREAT winter project. Welcome to E-fuels.

4. While you're at it, replace every fuel ine you see.

[HighTrim]

I would verify that you are sparking on all cylinders. The fact that she runs on the muffs, but not under load points me in this direction.

Do you have an inline spark tester and know the procedure for this? All cylinders should spark with a bright blue snap, and jump a good 7/16" gap.

[voltron]

My brother and I checked compression ..120 in all 3 cylinders. Checked plugs..good spark out of all three. Took off air box cover, a little gas leaked as we undid the screws. Noticed no air filter..being our first outboard, didn't know there is not supposed to be one, but now we know. throttle flaps moved in unison..so, going to re-build carbs. Notice the insulation on the boat motor cover is flakey and is on some of the engine parts when u take off cover...thinkin this may be pluggin the carbs?? Might remove the old flakey insulation. Thanks again for the help and will posts my results.