1977 85 HP. Misses/Cuts at idle and low speed

[jaynang]

Ok gentlemen, I put a 1977 85 HP Evinrude outboard on my boat. Replaced the lower end b/c I had the wrong shift cables and it wore the clutch dog down in a hurry.
Now that the lower end is fixed I am having another issue. It is difficult to start and runs on what best I can tell is 2-3 cylinders on idle up to mid throttle. Once you get underway you can hear the missing cylinders pick up and the power triples until they cut back off again. This only happens at low to mid throttle.
I have rebuilt the carbs and completed a decarb and ensure the fuel pump was working. This in my mind pretty well removes any doubt that it's electrical.
I just purchased new plugs for it since I now believe it's in the fire.
I want to make sure I'm not off base here, If it was a coil it would be doing it at top end instead of bottom. It had 2 different brands of plugs in it, all look fine and none are wet when pulled but they aren't the Champions that I bought to replace them.
In short, my question is..has anyone else on this board had the same symptoms with their 85 HP Evinrude of missing/cutting until top end?

 

[emdsapmgr]

Re: 1977 85 HP. Misses/Cuts at idle and low speed

If the engine runs fine at top end, unlikely that you have an ignition problem. Very possible you have some debris in the carb passages, even the idle jets. During carb overhaul did you use an aerosol carb cleaner to spray out each carb passage? Also, remove and inspect each jet visually? It is also possible you need to verify your sync and link settings.

 

[jaynang]

Re: 1977 85 HP. Misses/Cuts at idle and low speed

I used an aerosol spray cleaner as well as compressed air. Instinct tells me that it is a fuel problem as well but all passages were clear on rebuild. Jets did come out.
I will pull them off again this weekend and recheck.
I may have forgot to put in the original post that my fuel economy is horrible.
I understand outboards aren't known for being green machines but I will burn through 6 gallons of gas in less than an hour without the throttle pegged.
The last tank had seafoam ran through it as well.
Compression on all cylinders are between 115 and 120 PSI

 

[emdsapmgr]

Re: 1977 85 HP. Misses/Cuts at idle and low speed

These engines were always pretty thirsty for fuel, even the 85 hp engines.