1975 Merc 500 No Low to Mid Idel stalling NEED HELP

[MADMERCOWNER]

I have a low idel problem. When I start my outboard it runs for about 20 seconds then starts to stall. To keep it running I have to tap the choke. Then it will rev up again for about 5 seconds. I have to continue this process just to keep it running. If I tap it too much she stalls.When I put it into gear I have to do the same thing up until it is over half throttle. At full throttle she runs sweet. There is fresh high octane fuel and vented-new fuel pump-new fuel lines and a fresh tune up. Now what. Hope you guys can help! Thanx

 

[12Footer]

Re: 1975 Merc 500 No Low to Mid Idel stalling NEED HELP

Check the compression. I suspect one or more low cylinders, but maybee not. But without it, no sence in proceding, because everything hinges on that.

 

[MADMERCOWNER]

Re: 1975 Merc 500 No Low to Mid Idel stalling NEED HELP

Did compression check. 130 to 140 across all 4 cylinders. Is it possible only one of the two carbs is not working. I used that gum out carb cleaner and when I would spray it in the top carb the engine would slow down until I stop spraying. But in the bottom one no effect at all.