I just bought a used 16ft 1975 vhull it has a 20hp  mercury tillerd handle and its probly form 1975 to (not sure). and i got to pull start it and i cant find the idle on it. on the handle it says shift, then start, then fast ive crancked it up and it sounds  like its wide open, i havent tryed to crank it in the water yet but i have in my drive way. can anyone tell me how can find the idle on it i dont wont to through my self out the boat.

Idle screw is located on the carb.  Usually just above the bowl.  It will be a small screw running through a tension spring.

what do i do to the screw do i lossen it ir tight it up.

one thing you have to remember is that its always going to be moving or in gear.  it wont just sit still due to the disc always being engaged.

LEFT- idle down

RIGHT-idle up

HOWEVER, this sounds more like a frozen throttle cable.

we think its the choke on it. I might have to just brake down and have someone take a look at it.

I hope you have some muffs or other water supply when running it in the drive. If not when you have someone look at it they had better replace the water pumo impellor.

Are you talking about how to make it sit and idle in neutral while you start it, so it isn't starting in gear?

If so, there should be a forward/neutral/reverse shift on the motor, probably on the side.

I'd suggest you buy a Clymer or Seloc manual for it. Your local marine supply place should be willing to tell you the year from the serial number.

Also, as NBR said, if you haven't been running on muffs or in a barrel full of water, you'll need a new water pump impeller; they fry in about ten seconds, and you'll blow the motor. If it hasn't been replaced lately, or you don't know, it's a good investment anyway, especially if the boat has been sitting unused. They dry out, and don't work. By the time you find out it's bad, your motor can be toast. It's not hard to do yourself with a manual, or it's not that expensive a job to have done.