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2012 Tohatsu 6hp won't idle

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bullfrog88

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Hi - I bought a 2012 6hp Tohatsu 6 hp (maybe 50 hrs on it) from a buddy that changed the oil but way overfilled it (2x the correct amount of oil). I read the forum and see that causes major issues so i changed the oil (it smelled like gas) but it still runs rough and won't idle. If there is any good news it was only run with the excess oil for 10 mins connected to the hose but it was long enough to make the oil turn dark brown. Did we riun the motor? Any input would be appreciated.
 
Assuming your model is MFS6C; year is irrelevant. Verify oil level is between the hash marks on the dipstick when it is screwed all the way in. Odds are the excess fuel in the oil was from flooding, possibly due to not disconnecting the fuel primer hose overnights; that can also damage the fuel pump, causing fuel to pump into the crankcase. Poor idle is usually due to varnishing in the carb, usually due to not running the carb dry at the end of each day. A proper carb cleaning -- with real carb dip -- will probably get everything back to normal.
 
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Hi - pulled out the spark plug - end was full of black soot - i will get another one when i get a chance this weekend let you know how it goes. Thanks for all your help - appreciate it.
 
bullfrog88 said:
Hi - I bought a 2012 6hp Tohatsu 6 hp (maybe 50 hrs on it) from a buddy that changed the oil but way overfilled it (2x the correct amount of oil). I read the forum and see that causes major issues so i changed the oil (it smelled like gas) but it still runs rough and won't idle. If there is any good news it was only run with the excess oil for 10 mins connected to the hose but it was long enough to make the oil turn dark brown. Did we riun the motor? Any input would be appreciated.
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I’ll throw in my two cents as a newby “mechanic”. Hopefully it will help someone. Had the same problem. Removed the carburetor, disassembled it (at least I thought I had disassembled it), unscrewed the jet, and soaked it all in a carburetor dip for four hours. The carburetor looked like new. I reassembled it and reinstalled it. But only modest improvement. After some more YouTube searching I found reference to an idle jet. I removed the carburetor again and found the idle jet which was actually on the exterior of the carburetor and soaked the idle jet in carb cleaner dip for four hours. Put the jet back in the carburetor and the carburetor back in the engine and viola, idles beautifully.
 
Lasflyer said:
I’ll throw in my two cents as a newby “mechanic”. Hopefully it will help someone. Had the same problem. Removed the carburetor, disassembled it (at least I thought I had disassembled it), unscrewed the jet, and soaked it all in a carburetor dip for four hours. The carburetor looked like new. I reassembled it and reinstalled it. But only modest improvement. After some more YouTube searching I found reference to an idle jet. I removed the carburetor again and found the idle jet which was actually on the exterior of the carburetor and soaked the idle jet in carb cleaner dip for four hours. Put the jet back in the carburetor and the carburetor back in the engine and viola, idles beautifully.
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The idle air jet is not adjustable. It could get dust accumulation, which you apparently cleaned.
You do know that this post is two years old. The OP probably got things rectified by now.
 
Paul,
Hello, I have an '06 Nissan 6hp. I purchased it second hand from a person who virtually never used it(back up motor on fishing skiff). It starts and runs beautifully, but will not idle LOW. I have done all you suggest, but carb dip, which I will purchase today. My question: What are the factory settings for the Idle/Stop screw? I have both manuals, but I can find no reference to the Stop screw settings. The difference between too high idle and low/lumpy/surging/stalling idle is Maybe 1 or 2 degrees of turn on the screw. It almost seems like just looking at the screw throws it from one to the other.
It is driving me nuts...
 
Again, this post is years old. You really should start a new one.

I assume you have an MFS6B. Again, year is irrelevant, but model/serial is critical.

That characteristic is typical of a varnished low-speed circuit: when adjusted to low warm idle (1300 in N, 1100 in gear), the mix is a bit lean, and the motor wants to stall. Then, to cover up the issue, shade tree mechanics increase the idle, which puts the carb into the transition area. That fixes the majority of the mixture issue, but runs way too fast. After a Proper cleaning, that problem should resolve itself.

There is no set number of turns for the idle stop screw; You set the idle by tachometer.
 
@PACIFICMAN, probably the idle jet emulsion tube holes clogged. Simple zero dollar fix is to pull the carb off, open the bottom, clean out the jet and reassemble. See what that does for you. blow out all the passages with compressed air while you have it out. My sister's Tohatsu was doing the same thing and this fixed it.
 
Paul, Yes, MFS6B. Branded Nissan, but, you know...

O2B, I have opened the Carb and cleaned the Tube, holes, jets and seats, etc. It had no impact on the LOW idle. But I appreciate the input. I am going to do a "Dip" soak clean and blowout. Hope that will get it idling Low and consistent.

Thank you both.
 
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NSF6B idle speed in neutral should be 1300. In gear in the water, 1100. Use a shop tach to check that.
 
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