How many idle screws, and how to adjust.

[kriphead]

I have an 1989 90Hp Mariner 2 stroke, 3 cyl outboard motor.

I unfortunately decided to mess with 3 screws on the side to see if I could get a slightly better idle, and now I have problems, and can't remember the initial settings.

I want to know if in fact this motor has 3 idle screws? I have attached a picture, which locates the 3 screws I have been messing with. It is kinda hard to see on the pic, but they are spring ajustable scews, and they turn in and out.

After I starting messing with them, I now experiencing not being able to start the motor. If I then lean them all 3 to where I can start them, I get a delayed reaction when I give full power.

Please help. I really have a hard time understanding how to hear if the engine is not firing correctly, as fx. I can lean 1 screw all the way shut without too much happening to the idle or sound????

 

[achris]

Re: How many idle screws, and how to adjust.

Those are the idle mixture screws, one on each carb. The initial setting for them is 1-1/2 turns out from LIGHTLY seated.

If you don't have the Merc service manual, download it HERE, the password for the file is <ribforum>.

The full setup is on page 3A-17.

Chris.........

 

[kriphead]

Re: How many idle screws, and how to adjust.

Thanks achris,

I actually have this, I believe from you as well earlier.

I don't know how I missed this, as I have read the thing so many times (sometimes you get blind looking for something).. Thanks.

A few more, which are related to my problems and understanding:

Would it be fair to say that adjusting from that position "1?" out you would only need to adjust leaner? Also, would it be fair to assume that adjusting from the initial position should only be slightly, say 1/4 + 1/2 a turn? or is it really individual and could be several turns both ways?

Also, can I sorta use the same setting for all 3 screws or do they have enough personality, so that I have to adjust them all seperate?

 

[achris]

Re: How many idle screws, and how to adjust.

T... do they have enough personality, so that I have to adjust them all separate?

That's the one. Usually (but not always) the initial setting is reasonable close, +/- 1/4 turn....

 

[kriphead]

Re: How many idle screws, and how to adjust.

Thanks. You have been most helpful. I will hit the lake tomorrow morning and see if I can get my good ol' motor back in shape. I should never have tinkered with it to start with.

What if I think the engine sounds good, but accellerates kinda slow or bogging, do I then adjust all 3 slightly richer?

 

[achris]

Re: How many idle screws, and how to adjust.

What if I think the engine sounds good, but accellerates kinda slow or bogging, do I then adjust all 3 slightly richer?

Yes...

Just a word on those engines... They idle like a bag of sh1t....

Chris.....

 

[kriphead]

Re: How many idle screws, and how to adjust.

Ahhh, yes they do........ I think I will just have to accept that and make peace with it.