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Old 07-09-2014, 05:50   #1
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Tohatsu 9.8 Outboard runs poorly

My 2006 Tohatsu 9.8- 4 cycle outboard which has served me well through 2 seasons in the Caribbean and 3 years in Europe has just started to run poorly. After cruising the Maine coast for several months on the US ethanol laced gasoline I noted it started to run worse and worse. Hard starting and poor idle. I installed new spark plugs properly gapped. I added fresh fuel, with stabilizer, added some carb- fuel injector cleaner to the fuel. In took off the top of the carb and used spray carb cleaner to flush out all the the accessible passages. After all of this one day driving the dingy at full throttle it just died like it wasn't getting any fuel. I pumped the bulb on the fuel line and it was hard & I was able to restart the motor but only could keep it running by using partial choke. Using partial choke I was able to get back to the boat.
I removed the carb, and verified the fuel pump was pumping fuel when the engine was turned over.
I disassembled the carb completely and inspected and cleaned the main and idle jets. Note, they appeared to be clean when I removed them. I sprayed carb cleaner in every passage I could find. verified the float and its valve looked proper and was set correctly, I did note what appeared to be corrosion or brown deposits in the bowl of the carb. I cleaned the inside of the bowl the best I could. I reassembled the carb and re-installed and it starts right up but will only run if I keep it half choked. Note this is one of the EPA certified carbs where there are not adjustable needle valves like in the old days.

Before I replace the carb, any wisdom out there?
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Old 07-09-2014, 06:27   #2
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Re: Tohatsu 9.8 Outboard runs poorly

Any chance there's a clogged-up fuel filter in the system?
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Old 07-09-2014, 06:49   #3
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Sounds dumb but check the fuel connection on the motor had same problem when squeezing the ball gas would come out the quick connect replaced it and solved my problem I think it was sucking air
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Old 07-09-2014, 07:10   #4
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Re: Tohatsu 9.8 Outboard runs poorly

Ethanol fuel, dogonnit, will stiffen and warp outboard fuel pump diaphragms and the rubber tip on CARB's inlet needle.
If it's not an air leak, you can get carb rebuild kit and a diaphragm for the fuel pump- this is cheaper than total replacement, but means you gotta rebuild the parts if you're cool with it.
If Tohatsus tiny inline fuel filter (the one leading to carb) is the thread on type, their o-rings will developed air leaks from age/ethanol.
Good luck! Those are great little motors!
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Old 07-09-2014, 07:26   #5
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Re: Tohatsu 9.8 Outboard runs poorly

Wish I could be some help. I have a 9.8 2007 nissan (same motor) I have not had a problem YET.. Good luck.
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Old 07-09-2014, 07:37   #6
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Re: Tohatsu 9.8 Outboard runs poorly

I had a 9.8 hp Nissan (made by Tohatsu) that ran perfectly until I let the fuel get old. I just kept soaking and rinsing the carb in carb cleaner, over and over, and it finally perked up again.

Once mixed with 2-stroke oil, gasoline has a definite (relatively short) shelf life. I started discarding mine after it was a month old and never had any more problems.
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Old 07-09-2014, 10:20   #7
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Re: Tohatsu 9.8 Outboard runs poorly

Only way I have ever had much luck cleaning carbs is to remove and dis-assemble them and soak the pieces in carb cleaner, the kind that comes i a 1 gl can, is sold at any auto parts store and has a screen type of container inside to put all the little pieces in, just no plastic or gaskets, the carb soak will eat those
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Old 07-09-2014, 10:50   #8
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Re: Tohatsu 9.8 Outboard runs poorly

s/v Angel has the right diagnosis or is at least letting you know the culprit. I only use non-ethanol fuel in my small engines and I run them dry either by shut off valve or disconnecting the tank. I do that after nearly every use except with lawnmowers. The not being able to idle symptom means you need a carb rebuild.
Please let us know if you are able to get her running good again and what you did to fix it.
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Old 07-09-2014, 11:29   #9
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Re: Tohatsu 9.8 Outboard runs poorly

In my case it was the fuel pump diapragm. Of course I rebuilt the carb three times before I decided to look elsewhere...
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Old 07-09-2014, 21:22   #10
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Re: Tohatsu 9.8 Outboard runs poorly

Quote:
Originally Posted by onestepcsy37 View Post
In my case it was the fuel pump diapragm. Of course I rebuilt the carb three times before I decided to look elsewhere...
Well, there's another possible problem.
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