Logo
FULL SITE MENU

9.8 Tohatsu 4 stroke problem...

M

massflyfishing

New member
Hi Guys,
So my new to me engine has been running great until tonight, thank god I had the emergency paddle! Engine started right up but I got some weeds wrapped around the prop and she stalled after a few minutes of running out from the boat ramp. I then cleared the prop and restarted as if it was a cold start, she started right up and I went full throttle across the pond, the engine ran fine for a minute and then coughed and died. I realize I had left the choke on so that was the problem but I could not get the engine restarted. After paddling for five minutes I restarted the engine but it would only run with the throttle up and when put in gear it died.

Upon returning home I was able to get her restarted but only with throttle on, as I came down to idle she would sputter and die. Could the carb be clogged?

Thanks,
Zach
 
So here's what I've tried so far:
1. New plugs
2. Pulled carb and cleaned using carb cleaner...there was no visible debris or gunk in there

So, could it be the fuel pump?
thanks,
Zach
 
Perhaps another clue...after I reinstalled the carb and pumped the ball, prior to starting, I heard some air hissing around as I pumped the ball. Could I be getting air in the line somehow?
thanks,
Zach
 
The saga continues:
Since there's spark, the carb is clean, and it runs I figure it's got to be the fuel system. I was able to easily get fuel from the tank to the fuel pump easily, however when I tried to get fuel from the pump to the carb by turning it over with the spark plugs unplugged I just got a few drops of gas...so I'm thinking it's a faulty fuel pump. I pulled the pump, disassembled it and there were a bunch of cracks and corrosion in and on the pump. Does it sound like I've found the culprit?
thanks,
Zach
 
massflyfishing said:
So here's what I've tried so far:
1. New plugs
2. Pulled carb and cleaned using carb cleaner...there was no visible debris or gunk in there

So, could it be the fuel pump?
thanks,
Zach
Click to expand...

Carb cleaner is not aggressive enough. You need a 4-hour soak in carb dip, followed up by a blow-out with carb spray.
 
massflyfishing said:
Perhaps another clue...after I reinstalled the carb and pumped the ball, prior to starting, I heard some air hissing around as I pumped the ball. Could I be getting air in the line somehow?
thanks,
Zach
Click to expand...
Probably hearing the air purging out at the carb needle as the fuel line is filling the carb. Also, while priming a dry carb, the fuel will hiss as it squirts past the needle, until the float comes up.
 
massflyfishing said:
The saga continues:
Since there's spark, the carb is clean, and it runs I figure it's got to be the fuel system. I was able to easily get fuel from the tank to the fuel pump easily, however when I tried to get fuel from the pump to the carb by turning it over with the spark plugs unplugged I just got a few drops of gas...so I'm thinking it's a faulty fuel pump. I pulled the pump, disassembled it and there were a bunch of cracks and corrosion in and on the pump. Does it sound like I've found the culprit?
thanks,
Zach
Click to expand...
You may have a low-performing fuel pump, but that would usually limit top speed, not idle. As long as the check valves, spring and diaphragm in the pump are working, you should be OK. If in doubt, change the pump and o-ring. If there is corrosion in there, you have been pumping water (in some form). A water-separating filter is a good idea... and try to run only non-ethanol fuel.
However... your symptoms point to a carb varnishing issue. Do a Proper soak and clean, and the carb will probably work a lot better.
 
Thanks for all the help Paul, you were right, it was the carb. I replaced the fuel pump and the oil yesterday and still no change, so I pulled the carb (again) and realized that I hadn't fully accessed the jets during my initial cleaning, looked through the low speed jet and there was a tiny obstruction...cleaned that out, remounted the carb and she ran perfect! The good news was that I had never: pulled a carb, changed a spark plug, or installed a fuel pump so I learned a ton about my new motor.
Thanks again for the help.
Zach
 
Glad it worked out. In the future, run non-ethanol fuel, and always run the carb dry at the end of the day (unless you know you will be running tomorrow) to reduce buildups in the carb. The 9.8 can also benefit from a water-separating filter.
 
Back
Top