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Tohatsu troubles

9K views 56 replies 21 participants last post by  cthoops 
#1 ·
We have a 2010 Tohatsu 9.8 hp outboard on our boat. The previous owner said it could be temperamental.

It ran pretty well for the first six weeks or so, but now it either runs very smoothly, or it's very rough and acts like it wants to stall (and occasionally does). When it's running rough, increasing/decreasing the throttle or fiddling with the choke doesn't help it. Yesterday we went to the dock to get water, etc. and it purred right along. On the way back, it stuttered away (made for a stressful return to the mooring).

Before the season we put in a new water/fuel separator filter, we always run it dry, and we use high octane fuel and put stabilizer in it. We top off the tank frequently (it's an external 3+ gallon tank), and it gets used once a week.

At this point we're not comfortable heading out for a sail until we get it straightened out. Any thoughts? Would it be something that we can try to fix ourselves? Mr. Cthoops was an airframes mechanic 30 years ago in the Marines and he can fix any bicycle, but he doesn't consider himself a motor head. I'm really good at cheering him on and handing him things.

Any suggestions would be greatly appreciated. Thanks.
 
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#4 ·
The electronics are so good on these now that it really has to be the fuel system. Makes it simple. Either the carb needs to be cleaned (which is very easy) or the fuel lines and/or connectors need to be replaced.
 
#5 ·
We have a 2009 Tohatsu 9.8, with what sounds like the same issues. I had the carb rebuilt about 2 weeks ago, and it ran great until last Sunday. I ran it dry and started it again on Friday, and we are back to square one.

I had been leaving the fuel bowl full since it sat no more than a couple of days at a time, but Sunday I decided to run it dry. My very amateur thought is that when it is really warm (it has been in the 90's) that running it dry caused the problem, since the fuel evaporates much more quickly in the heat, leaving behind the varnishes and residue that wrecks fuel systems.
 
#6 · (Edited)
Its probably the carburetor which is easily disassembled and clean using a Carb cleaner. You will be surprised just how easy it is.

I have the same engine, it was stored for a couple years and had problems running smooth. I took apart the Carb and cleaned it and of will start on the first pull and runs smooth as ever.

The fuel is the problem, not the engine
 
#8 ·
"Running it dry" will leave a small amount of fuel in the bowl. Suggest you drain it instead. Just had the same problem with my generator which I haven't run for a long time.
I drain the carb after each use. Anyway, I dropped the bowl, which was perfectly clean, turned the gas on and manually "tickeled" the float up and down many times. It worked, ran perfectly without having to remove the carb.

Removing the carb and cleaning the jets and air passages is not difficult. Suggest you work over a large towel and place the parts top side up in the sequence, cleaning with a thin wire, compressed air and/or spray carb cleaner. No hands on experience with your particular carb but have done many others. Be aware of little check balls and/or springs, work slowly and carefully. Worst case is if your fix doesn't work you can take it, the carb, to a shop. Agree with the earlier post that modern ignitions are basically bullet proof.

Paul T
 
#9 ·
These are all great suggestions with your theories confirming ours - that it's likely the carb. We've never removed one before so it should be entertaining, but I'm taking to heart the fact that it doesn't seem to be a difficult job.

Would it be better to use the spray cleaner or should we let it soak in the other stuff?
 
#17 ·
These are all great suggestions with your theories confirming ours - that it's likely the carb. We've never removed one before so it should be entertaining, but I'm taking to heart the fact that it doesn't seem to be a difficult job.

Would it be better to use the spray cleaner or should we let it soak in the other stuff?
You can try mixing about a 50% mix of gas & cleaner. Run it, let it set for a day or two, you might get lucky.

I have used a combination of spray cleaner , thin wire and compressed air. Never had to soak the whole carb but it might help if the first attempts don't work. I have used Berryman's B-12 fuel conditioner/ cleaner for many years. Other products may be as good. Be careful, Berrymans can remove paint.

Paul T
 
#12 ·
Can't remember the exact HP, I think 2.5. One of the biggest mistakes I have made. Took it back to Boat US a day or two after I bought it and they would not replace it. We took it apart outside the store and found the carb bowl full of gas. Drained it and it ran ok for about one day. Finally took it to their authorized dealer and they told me it was dirty gas. Well gas was only about 1 week old. anyway they cleaned the Carb, charged me $80 and told me I should have bought it from an authorized dealer in the first place.
About a week or two later I took it on a short cruise and guess what, it wouldn't run again.

I will never never never buy any product made by Tohatsu. They are crap.
Got rid of it and bought a Suzky 2.5 four stroke. Believe it or not, same problem. This time I took it back to the dealer and the factory replaced the Carb. Finally it worked.
THE JETS ARE TOO SMALL.
 
#16 · (Edited)
I will never never never buy any product made by Tohatsu. They are crap.
Got rid of it and bought a Suzky 2.5 four stroke. Believe it or not, same problem. This time I took it back to the dealer and the factory replaced the Carb. Finally it worked.
THE JETS ARE TOO SMALL.
I believe it because its not the engine, its the fuel, ethanol that is. You proved it yourself in your statement highlighted above.

I have not had my Tohatsu 9.8 for long, three years, but I am very satisfied with it. They also make the small Mercury and Nissan's, just different labels and some minor differences.

In any of the smaller engines using something like Sta Bil and running it dry will pretty much eliminate any issues with starting or idle/running...if long term storage such as winter, I would also drain the bowl.

I'll mention it again, there is really no need to waste $80+ on a mechanic, the carb on the Tohatsu is so easy to clean its silly. Cant say the same for Honda.
 
#13 ·
I have a Tahotsu 9.8 and have only use ethanol free gas. I have never had a problem. I don't think it's Tahotsu that's the problem it's the fuel. Mercury dealers here in Canada, probably in the USA as well, have been told to tell there customers to avoid ethanol gas. They too will not cover ethanol related problems.
 
#18 ·
I have seen a few threads like this one with people advising to use non-ethanol gas, run the carb dry after use, drain the carb, dump gas older than 30 days, ect., and it is all is good advice, but I find it a little strange that I can put ethanol gas in my lawn mower, leave it sit all winter, and in the spring it starts right up. Ok, so I don't advise doing that to your lawn mower, and I understand that a lawn mower is not the same thing as a marine outboard engine, but why don't they make them a little more lawn mower like? A little more forgiving, a little more bullet proof? they just seem to be overly fussy. Is there some kind of reason for this?
 
#20 ·
A friend of mine researched this

We at TSBB had several conversations about this, and Bill Butts called the manufacturer who told him they are required to sell new motors with a the small-jet carbs due to EPA requirements, but could sell an after market replacement that isn't allowed on motors sold as new. I took his advice, and bought Item ID:354, 0.07CARB 3R4032001M from Internet Outboards. My OB is 6 HP 4 stroke.

That was in 2009, but I had to stop sailing before getting the boat back in the water. I just got her back in the water in May, and have had no trouble so far.
 
#21 ·
We're going to give it a go at cleaning the carb ourselves this weekend when we're down at the boat. Hopefully giving the carb a good clean will take care of it.

We also found a place to get ethanol-free gas approx. 60 miles from here. Frankly, if that's what's causing the problem we will gladly make that drive with a few 10-gallon portable tanks to stock up!
 
#29 ·
We're going to give it a go at cleaning the carb ourselves this weekend when we're down at the boat. Hopefully giving the carb a good clean will take care of it.

We also found a place to get ethanol-free gas approx. 60 miles from here. Frankly, if that's what's causing the problem we will gladly make that drive with a few 10-gallon portable tanks to stock up!
Your motor is rated at 1 gallon per hour fuel burn at 5500 rpm. That said you can run at full throttle for about 3 hours on a tank of gas. In reality you will not be running nearly that much gas through it. I wouldn't stock up on a bunch of bulk fuel unless you have some other gasoline sucking equipment to use it in.
 
#22 ·
If you drive that far, and stockpile that much gas, you'll find yourself using very old gas in your motor, which can also cause problems. One advantage to a four stroke is that you can burn off your gas in your truck and never use old fuel for the outboard. Do you really want to take a chance on last year's gas stranding you in the bay?

I'd keep looking for a local source, or better, add a fuel treatment like seafoam.
 
#23 · (Edited)
The one problem I had was when I forgot to drain the carb on my Honda 2 HP 4 stroke outboard. The float bowl was full of nasty debris. I have a Honda generator that I replace the fuel once a year. It starts right up on the year old fuel. Did have a small problem with debris or a stuck float but not sure it was because of old fuel, maybe stuff in the tank, it is over 20 years old. I do, however, drain the carbs on my outboards, snow blower and generator. Running them dry leaves a small bit of fuel in the bowl.

I have also used this for many years:

B-12 Chemtool® Carburetor, Fuel System and Injector Cleaner | Berryman Products

FWIW, I bought a new Tohatsu 6HP 4 stroke about 2 years ago. Use it a lot, ran/runs perfectly right out of the box at 6,000 feet elevation, no tweaks or adjustments necessary.

Paul T
 
#24 ·
We always make sure we use Ethanol free gas in our Tohatsu. And we still add fuel treatment to lengthen the life of the fuel. I have the same year but a 6hp version and it has be flawless,,,,,so far.

If possible, don't stock pile gas, even ethanol free goes bad in no time at all. Most all fuel docks have ethanol free gas.
 
#26 ·
JUst bought a new carb for our 2009 20hp Tohatsu that flipped in Hurricane Sandy. It now runs like new. I figure that will give me plenty of time to clean the old carb, and it was relatively inexpensive (10% of the cost of a new engine).

In prior years, we had a problem that we had to "rev" the engine constantly (like motorcyle riders do, up and down rapidly with the rpms). I'd be curious to hear whether your engine needs "rev-ing". When we replaced the gas the problems went away. remember to drain the bad gas out of the hose too.

Regards,
Brad
 
#27 ·
I heard that plastic gas tanks deteriorate and clog carbs.

Regards,
Brad
 
#28 ·
I can only speak from my own experience of having plastic tanks on many motorcycles and outboards for over 40 years. the only fuel related problems I have had were related to forgetting to drain the carb for long periods of time.

There are probably many different types of plastic tanks so it may be a possibility? If they deteriorate you could probably see the debris in the tank or they may start to leak?, which would be very bad, especially with a permanently mounted tank.

Paul T
 
#30 ·
rhr1956 -

We usually run our 8hp Tohatsu with the throttle just cracked open and it quietly pushes our 24' boat along at around 3.5 kt in smooth water. In rougher conditions, we might open it up a bit more. Only when pushing into pretty heavy wind (30+ kt) and sea do we have to open it to maybe half throttle. Do you have any idea what the fuel consumption might be under low throttle conditions?

I've been figuring maybe 1/2 gallon per hour, but haven't been able to find any good information. It would be good to know to get an idea of our motoring range.
 
#32 ·
rhr1956 -

We usually run our 8hp Tohatsu with the throttle just cracked open and it quietly pushes our 24' boat along at around 3.5 kt in smooth water. In rougher conditions, we might open it up a bit more. Only when pushing into pretty heavy wind (30+ kt) and sea do we have to open it to maybe half throttle. Do you have any idea what the fuel consumption might be under low throttle conditions?

I've been figuring maybe 1/2 gallon per hour, but haven't been able to find any good information. It would be good to know to get an idea of our motoring range.
Not really...I found the info on one of the Tohatsu websites. It showed the 9.8 4 stroke burning 1 gal per hour @5500 rpm. The 6hp 4 stroke burned 0.5 gal per hour at similar rpm. My motor is the 6hp and I have yet to burn a full tank in an entire summer-and we go a couple times a week. Bottom line is...they don't burn much gas.
 
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