Date: 10/27/2008
Name: Dave Doan
email: daved@rapidnet.net
subject:Tohatsu 4 hp 4 stroke
I couldn't resist going out to the garage to look at the carb on my 6 hp Nissan outboard. A Tohatsu 4 hp should be pretty much identical except for the calibration. As Mike mentioned, the only adjustment is for idle speed; no mixture adjustments at all. The described symptom of running slightly better with the choke pulled does indicate a lean condition. Assuming the fuel supply is not the problem (gas in tank, filter not plugged, etc.), the next logical step would be to remove the drain plug in the bottom of the float bowl. Try to catch the drainings to look for dirt or water. If it looks ugly, a disassembly/cleaning is probably in order. As a last resort one might try a shot of compressed air in the bowl.The idle (pilot) jet can be accessed from the top without disassembly. Look for the brass plug with a straight screwdriver slot about under the throttle link. When you see how small that orifice is it's no longer a surprise that they tend to plug up. A bit of air at that point might also help. The main jet is at the bottom of the float bowl and can only be reached by removing the bowl. Interestingly, right next to the idle jet is another plug which is pressed in so as to not be removable. This covers the idle mixture adjusting screw which is factory set. Best to not mess with it unless you know what you're doing and even then only as a last resort.
Tohatsu.com offers downloadable owners manuals. Onlineoutboards.com offers service manuals for 30 bucks.
One last comment; no need to get a kit unless a gasket is obviously bad. Really all that's neccessary is to get that float bowl off and clean out the junk.
I've run my 6 hp on a sawhorse with the bottom end in a 5 gallon bucket on occasion; just don't put it in gear! (Don't ask me how I know that!)
Cheers,
Dave
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