Mercury 18hp will not start. Please help!

[dixie189]

I recently purchased a 1981 Merc 18hp. It had been sitting awhile. I cleaned the carb and replaced the fuel pump and gaskets, replaced the spark plugs, water impeller. It will only fire and run if i have it in forward gear and full throttle. Even then it takes forever and many many hard pulls to get it to fire. It fires and then will stay running, I back off the throttle so it isnt over reving. Will run fine at a higher speed, still in gear.. but when i drop it down to idle it dies immediately. I cleaned the contacts on the coils.. it has a nice strong blue spark. Has new clean fuel in a new tank. Idle screw is backed out 2 full turns, I tried 1 1/4 like the book says.. made no difference.
Ideas anyone?

 

[MH Hawker]

Clean the carb again and blow out ever port and passage and in stall new floats.

 

[dixie189]

Clean the carb again and blow out ever port and passage and in stall new floats.

I cleaned the carb 3 different times.. soaked the parts over night.. blew out all the ports and passages with compressed air. Other than leaking..what would be wrong with the float? I checked mine to see if it floats and if it leaked.. which it does float..no leaks.

 

[MH Hawker]

floats get heavy

 

[herdsman]

Good chance the even with cleaning the idle passages and jets could still be clogged with some gunk, they're sometime very hard to get open. Other than that, maybe weak fuel pump?

 

[Guest]

have you verified both cylinders have good compression? i had the same symptoms on an 87 force 15. Hope thats the issue but good to check

 

[dixie189]

have you verified both cylinders have good compression? i had the same symptoms on an 87 force 15. Hope thats the issue but good to check

Have not checked the compression yet.. will for sure check it and post the results.