Tohatsu 9.8 idle screw

[wgoepf]

I know, the screw for idle is nr. 3. But which function has screw nr, 4. What is happen, if I push this up or down ? How I must adjust this screw?

 

[Sea Rider]

Welcome to Iboats,

The other one is the air/fuel mixture screw, if OB maintains a smooth idle don't play with it unless you know how to adjust that screw well...

Happy Boating

 

[pvanv]

What is your actual model? On the MFS9.8A3, there is the idle stop screw, which adjusts idle throttle. On that carb, if manual choke, there is also a screw to advance the idle throttle when choking. On all 9.8 carbs, it is also possible to adjust the low-speed air/fuel mixture, but, as Luis noted, don't tinker with that unless you are an expert.

 

[wgoepf]

Hallo, my Typ is EP(remote)
I have Information. The screw nr. 4 is not for mixture air/ fuel. It is the screw for ACCELERATION PUMP! Not all typs of tohatsu 9.8 have this pump! My question, what is changing, if I turn this screw?

 

[pvanv]

OK, so you have a 9.8 4-stroke; European model. The US info does not describe that carb; it was used on some Mercury 9.9 (Tohatsu 9.8 power head) motors. Changing that adjustment is seldom if ever needed, but it changes the timing and stroke of when the accelerator pump operates. The accelerator pump is to counteract stumble when the throttle is rapidly opened. The US models don't even have one. I would not adjust it, unless you are either dumping too much fuel, or getting too much stumble when accelerating.