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meboater 06-21-2013 09:02 AM

Tohatsu help
The Saga that is my sailing season continues.

3 year old Tohatsu 8 hp. Ran fine in a tank at my house pre-season. I transported it to the coast in the correct position.

Still starts easily and runs perfectly smoothly, now that the boat is in the water. Had I not opened the throttle while on the mooring, I would have never suspected a problem.

But, give it a minute amount of throttle, and it responds appropriately, with a slight increase in idle. Give it any more, even very gently, and it dies.

My first thought was air starved/ bad air filter. Or, less likely, not able to draw enough fuel because of a kinked hose, fuel filter, etc. I no longer think that because:
  • I disconnected the tube running from the filter to the carb- no change.
  • I briefly disconnected the fuel line between the carb and the filter, allowing it to run on what was in the fuel line for a bit- no change.
  • And, if I pull the choke all the way out, it runs like it is nearly WOT. RPMs will increase slightly if I am full choke and give it some throttle.

All of the external linkage seems to operate smoothly.

My next thought is to pull the air filter, and to spray carb/choke cleaner directly into the carb, in the hope that there is some internal linkage sticking.

Anybody out there have any other thoughts?

Minnewaska 06-21-2013 09:14 AM

Re: Tohatsu help
Guessing carburetor. You can try a can of ValvTec Marine Motor De-carb as a cheat. You need to spray the whole can in. The only tough part is that the motor may need a few extra rpms to eat the stuff.

You may just be out of lean adjustment.

meboater 06-21-2013 10:04 AM

Re: Tohatsu help
An thoughts on where the rich/lean screw might be?

dabnis 06-21-2013 10:11 AM

Re: Tohatsu help
Likely some debris has formed during storage and is partially blocking the high speed jet, which is fixed. Before ripping the carb apart, as mentioned, try the spray or another carb cleaner, mixed at about 50% with fresh gas. Let it run, then let it sit for a few days and try again, you might get lucky. If it will pull with the choke on that is almost a sure sign it is starving for fuel, assuming the ignition system is up to par.

I have used this for many years with no fuel related problems:

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

Paul T

meboater 06-21-2013 10:33 AM

Re: Tohatsu help

deniseO30 06-21-2013 10:41 AM

Re: Tohatsu help
I had that same problem with a honda 2 hp. put straight gumout in the tank let it sit a few days. then added gas. it was fine after that. It' s the gas, I think it goes bad in a very short time.

dabnis 06-21-2013 11:14 AM

Re: Tohatsu help

Originally Posted by meboater (Post 1047395)

Appears the fixed high speed jet is restricted, see above.

Paul T

meboater 06-21-2013 11:54 AM

Re: Tohatsu help
Taking nominations for best easy fix.

I am a little frustrated right now, as this motor thing has turned into a saga. This Tohatsu ran like a charm, and it was on the boat just while the Yamaha was getting fixed. To sum u my recent challenges:

• Season 1- Bought boat with Yamaha. Ran a little rough.
• Season 2- Brought motor to shop, carb clean, ran great.
• Boat sat for a couple weeks, would not start at all.
• Brought carb to second shop. They cleaned the carb. Re-installed carb on last day of season to pull boat. Started and ran beautifully, but spit gas out of the bottom.
• Left carb at shop on my way home for the season. They replaced the accelerator pump diaphragm, which was leaking.
• Season 3- picked up carb, re-installed. Motor started and ran beautifully, but spit gas out the bottom of carb.
• Shop is reputable, but 1.5 hrs from house. 2 round trips = 6 hours driving time. Opted to have fixed locally.
• Re-installed carb. Motor ran perfect. Tested in a barrel, ran well at all speeds. Repeatedly.
• Went to launch boat, blew a brake line in truck.. Very lucky I did not launch the truck. Or crash on the highway.
• Returned a few days later when marina said they could launch me, as my truck is not fixed. Marina was too busy to launch me.
• Returned a few days later to sail. Motor does not work at all.
• Took Tohatsu, which had been fogged and stored properly, then tested multiple times at home. Transported it properly to marina, and enlisted their help to swap, as boat is on a mooring, and I have no truck yet. Tohatsu runs as described in my first post.

Sal Paradise 06-21-2013 12:12 PM

Re: Tohatsu help
Plugged carb. You should do this yourself. Go to Walmart get the 1 gallon bucket of carb cleaner with the screen basket inside. Take the carb apart, dip it for a couple hours and put it together and back on.

I can take the cab apart in less time that it took me to post this, almost.

MarkSF 06-21-2013 01:28 PM

Re: Tohatsu help
When you have finished running the engine, do you always run the carb dry of fuel? If not, you are constantly gumming up the jets, and it's a cumulative effect.

Another good habit is Stabil or similar in the fuel.

A third good habit is NEVER to use fuel that is more than one month old. Dispose of it in your car's gas tank.

Following these 3 habits, or not, can make all the difference, between a nightmare engine and a dependable one.

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