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S2 7.9 Bear Lake, UT
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Discussion Starter · #1 ·
This is not my Suzuki of the pervious post with oil in the carb but my Tohatsu 9.8hp four stroke.

I bought the engine 2-3 years ago. It has always started on the first pull as far as i can remember. I bought it used with less than 10 hours on it and put about 2 hours on it two summers ago, last summer it did not get started at all. Last weekend it started on the first pull I let it run a few minutes then shut it down by closing the choke and revving the throttle, after a few minutes of boat setup it would not start again. I finally got it started and it got me to the slip, but would not start the rest of the day or the next morning. I even tried starting fluid. I had to move slips so borrowed a SUP paddle. On day 3 it started on the first pull but ran rough and I quickly opened the choke and it died. I had to once again borrow a paddle to get to the ramp.

I brought the motor home and have removed the carb, which I will open and clean later today, which usually solves any outboard issues. Is there anything else I should look at while the motor is home on the stand? Found out it is not fun trying to work on an outboard while hanging off a transom.
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S2 7.9 Bear Lake, UT
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Discussion Starter · #3 ·
Carb is most likely. Other ideas... Did you remember to open the fuel vent? Check spark plug and wire? Fuel quality, if use was light last year
I have yet to check out the spark plug, I will do all the above. I only use ethanol free fuel and the fuel was fresh this year. Tank was vented. I was tempted to replace the fuel filter and check the spark plugs but knew I would have dropped something off the back. I will order a new air filter, fuel filter, and spark plugs to replace before putting the motor back on the boat.
 

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Tartan 37
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I have the same engine and it has mostly been trouble free using fresh fuel, I now only use fuel from the local airport which of course is ethanol free. But to your question... Last year I was having issues and ended up seeking a mechanic to look it over. Needed a new throttle body control or something like that, whatever it is that controls the shift, throttle, etc. It had essentially worn out.

I would add, the Tohatsu does NOT like the bulb squeezed to build pressure, not sure why, but don't do it I swear ;)
 

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Discussion Starter · #6 ·
I would add, the Tohatsu does NOT like the bulb squeezed to build pressure, not sure why, but don't do it I swear ;)
Thanks for the warning, I keep pumping the bulb when it won't start, hoping fuel pressure will solve my problems.

I cleaned the carb and it fired right up. There was obvious signs of fuel left in the float bowl when I cleaned the carb. I will now shut the motor down by removing the fuel line at the end of each sailing day.
 

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Thanks for the warning, I keep pumping the bulb when it won't start, hoping fuel pressure will solve my problems.

I cleaned the carb and it fired right up. There was obvious signs of fuel left in the float bowl when I cleaned the carb. I will now shut the motor down by removing the fuel line at the end of each sailing day.
Glad you got it going. That engine has a carburetor drain screw (see page 79 https://www.tohatsu.com/tech_info/own_man_pdfs/Toh_MFS8B_98B_003-11114-3AG1.pdf ). I have found that with most small outboards, removing fuel line and/or shutting off fuel valve (if it has one) and THEN draining the carb via drain screw if you are not going to use the engine for a few days is the best way to keep the carb happy.

A word of caution: most carb drain screws will fall out if backed out too much. One only needs to loosen it until fuel starts to flow. Here is the advice from the cited manual:

1. Disconnect the fuel hose from the out-board motor.
2. Remove the top cowl.
3. Place an approved fuel container under the drain screw and use a funnel to avoid spilling fuel.
4. Loosen the carburetor drain screw.
5. Tilt up the outboard motor until fuel flows out of the drain hole.
6. Leave the outboard motor in this position until all fuel has been drained.
7. When thoroughly drained, retighten the drain screw securely.

Good luck,

Nick
 

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The way I have been shutting down the outboard is to turn off the fuel while engine is running. As it approaches stopping I open the throttle and pull the choke to get it to run just a few seconds more in the hope all the fuel in the carb has been sucked up. Anyone else do the same?
 

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The way I have been shutting down the outboard is to turn off the fuel while engine is running. As it approaches stopping I open the throttle and pull the choke to get it to run just a few seconds more in the hope all the fuel in the carb has been sucked up. Anyone else do the same?
That method never completely drains the carb in my experience (but is certainly better than nothing). I do let the engine run out of fuel by shutting off fuel supply, but I found that pulling choke and running tends to "richen" the air/fuel mixture and carbon up the spark plug(s) making starting more difficult next time.

Nick
 

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Discussion Starter · #10 ·
The way I have been shutting down the outboard is to turn off the fuel while engine is running. As it approaches stopping I open the throttle and pull the choke to get it to run just a few seconds more in the hope all the fuel in the carb has been sucked up. Anyone else do the same?
I do something like this. Open the throttle and pull the choke to shut the engine down. It has worked in the past. I did it this time after starting the motor. It started on first pull ran smoothly for about 5 minutes. I then shut it down and the engine would not start 10 minutes later. My first thought was my shut down method was the reason it would not start but realize it is likely my insufficient shut down nearly 2 years previous that caused my problems.
 

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I do something like this. Open the throttle and pull the choke to shut the engine down. It has worked in the past. I did it this time after starting the motor. It started on first pull ran smoothly for about 5 minutes. I then shut it down and the engine would not start 10 minutes later. My first thought was my shut down method was the reason it would not start but realize it is likely my insufficient shut down nearly 2 years previous that caused my problems.
More than likely the remaining fuel turned into a varnish like sludge after two years and then when you ran the engine that mixture clogged the tiny jets in the carb. I have seen it so bad that the only option is to replace the carb.

That is why I recommend shutting off fuel supply and draining the carb (see above)


Nick
 
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