2009 Tohatsu 9.8 Running Rough

[thannah84]

I bought a brand new Tohatsu 9.8hp electric start back in April. I am using it as a kicker on my Lake Erie boat. A few weeks back I took it out to troll and discovered that it would not stay running. It would run at high rpm's with the choke out and that is it, even at that it was hard pressed to stay running. I took it home and got all the old gas out of it (Because between trips I did not unplug that gas line) and put new gas in. Same thing. I pulled the plugs. Looks dirty so put 2 new ones in. Same thing. Pulled the carb and cleaned it (Jet's, Float..etc) Put it back on and now it idle's but still is running very very rough and it's rpm's seem to go up and down without moving that throttle. Any ideas? It is still obviously under dealer warranty, but the nearest Nissan/Tohatsu is 95 Miles from me. Also, I started running the motor out of gas between trips and I also put Stabil in the tank. I am running 87 Octane out of it. Should I be running higher octane? Thanks in advance.

 

[pvanv]

Re: 2009 Tohatsu 9.8 Running Rough

Sounds like you still have a fuel problem. The fouled plugs were likely due to excessive choking. Go through the carb again -- carefully and deliberately. Variations in idle RPM are typically either a vacuum leak due to improperly installed carb at the base gasket (rare) or some remaining crud in the carb (likely). The 9.8 carb has small fuel passages, and needs to be very clean. Soak it in real carb cleaner -- not just the spray stuff, then blow it out carefully. If there's ANY question about the inline fuel filter, install a fresh one.

Verify the oil is not overfilled -- not even a drop. Running that rich can dilute the oil with fuel.

Run a water-separating fuel filter. 87 octane is fine. Try to get non-ethanol fuel (we have several marinas in Buffalo that advertise "No Ethanol". Close the tank vent when not using the motor.

Draining the carb is usually not necessary, unless the motor will be unused for a few weeks. The 9.8 has a large fuel reserve, and sips gas, so if leaving the motor unused for an extended period, draining the carb (you need an 8mm wrench for the plug) may be more practical than running the motor for 10 or more minutes.

 

[Lion hunter]

Re: 2009 Tohatsu 9.8 Running Rough

Doesn't a 3 month old motor have a warranty?

 

[thannah84]

Re: 2009 Tohatsu 9.8 Running Rough

Thanks Paul...I had the day off so I decided to try and tackle it this morning. Pulled the carb off and soaked it in carb cleaner (Not the spray stuff). Pulled it out, flushed with water and blew out with air. While carb was soaking, pulled plugs and cleaned them up and noticed the gap was very small. Measured them, they were only .025, I re-gapped them to about .038. Put them back in. Put the carb back together and re-installed. She fired right up and ran better and smoother than when she was brand new. Thanks for the response!!

 

[pvanv]

Re: 2009 Tohatsu 9.8 Running Rough

Doesn't a 3 month old motor have a warranty?

Warranty is 3 years. Does not cover things that are beyond factory control, such as incorrect plug gap and poor fuel issues.

 

[pvanv]

Re: 2009 Tohatsu 9.8 Running Rough

Thanks Paul...I had the day off so I decided to try and tackle it this morning. Pulled the carb off and soaked it in carb cleaner (Not the spray stuff). Pulled it out, flushed with water and blew out with air. While carb was soaking, pulled plugs and cleaned them up and noticed the gap was very small. Measured them, they were only .025, I re-gapped them to about .038. Put them back in. Put the carb back together and re-installed. She fired right up and ran better and smoother than when she was brand new. Thanks for the response!!

thannah,

Glad it worked out for you. BTW, that .038 plug gap is a little on the wide side. Factory spec is .8 to .9 (mm), which is roughly .031 to .035 (inches). While the spark on the 9.8 is quite strong, and they will run OK even at .040, the spark is more reliable around .035.

Best,

 

[thannah84]

Re: 2009 Tohatsu 9.8 Running Rough

Thanks Paul...Had it out today and it ran like a top...Smooth and quite....As far as taking it to the shop...After reading some posts on here, it seems quite common that if you leave the fuel line plugged in and you have exposed the carbs to some iffy gas, that you can bet the jets are clogged. I am not about to pay someone $100 an hour to clean the carbs when I am perfectly capable. Paul, you don't happen to know a lot about OMC Sterndrives do you...Another problem developed today on my main and am in need of some advice....In short, it is overheating at high RPM's and High Load...I have just posted about it if you want to read...Thanks Again!