Alan - I'd start with looking for a clogged fuel filter or a weakened rubber fuel line that is collapsing....if that's not it maybe look at the carburetor float as it could be saturated with gas. Those are great engines.

 

And make sure the gas tank is vented. As gas is consumed, air needs to get into the tank or a vacuum will form. Have that probably with my lawn tractor. Took two fuel pump replacements until I figured out to loosen the gas cap to keep her running.

 

In the carb body (bowl off), within the 'circle' of the float there a sort of pedestal with a rubber plug in it.. At the base of that there's a jet that can plug up and cause the symptoms you describe.

 

Remedy is simple ..... mark how many turns 'in' for all jets. disassemble the carb and use carb cleaner, precisely reinstall all jets to the previously made marks.

Next time when putting the OB away for storage for more than 2 months, run completely dry, drain the carb bowl, fill/flush the empty bowl with isopropyl alcohol -IPA (use a large syringe to load the bowl with IPA)

The carb on the Tohatsu 4,5 & 6 HP. has an extremely fine orfice in the idle trim adjusting jet which EASILY forms gum and varnish when the carb 'dries out' during long term storage.
Even if you use a stabilizer and store the OB for more than a month or two - seal the VENT on the carb bowl body to prevent evaporation of the gasoline to help prevent gum and varnish formation when the gasoline 'vaporizes' out through the carb bowl VENT (and again, even if you use 'stabilizers' in the fuel).

Best is to always run dry and then 'dump' the bowl via the drain plug; the IPA 'wash' will remove any 'already started' gum/varnish formation in the jets and orfices ... and in the bowl. A cleaned and dry carb bowl won't form gums, etc.; nor will have any 'phase-separated' fuel.

If you think you're having 'fun' now with 10% ethanolated gasoline, just wait until the newly mandated 15% EtOH gasoline 'hits' your OB.

 

It's likely fuel/air mixture, as others have given examples. Good winter storage ideas as well.

Ethanol is a high causal suspect. Hate the stuff. You can do a google search for land stations in your area that sell non-ethanol gasoline. It pays to haul it to the marina in a can. It also pays to religiously use a stabilizer, even during the season. Our OBs typically don't run enough, even in season.

 

Everything said above is spot on. One thing I will add: my father's Tohatsu sail pro suffered this same problem two different times. First time, it was clogged jet as RichH said. Second time, the fuel line connector between the hose and motor was not sealing properly. At idle, it was fine, but at any revs it would suck lots of air through the connection between connector and motor. We verified this with some soap and bubbles. Check your O-ring on the connector too and make sure it's not disintegrated.

 

At idle, it was fine, but at any revs it would suck lots of air through the connection between connector and motor. We verified this with some soap and bubbles. .

Yikes! You should never do this with soap and water - very bad for your engine when it gets sucked in like that.

The traditional way mechanics do it is to spray WD-40 instead. When it gets sucked in, it usually kills the motor telegraphing a leak. However, it is not harmful to get sucked into the carb.

 

Startron fuel stabilizer is the best I have found. Mix some gas heavily with a good 2 stroke oil and the startron 9even in your 4 stroke motor). Run it through the motor, shut off the fuel supply, let it run till it stalls. Then drain the bowl. When restarting after storage, open the bowl drain for 30 seconds and let the new/clean fuel flush the carb, then start.

The 2 stroke oil doesn't evaporate. I have found that when the fuel does, the 2 stroke oil is left behind and prevents 'bad gas' from sticking in the carb/jets. Thus, the fresh gas rinse in the spring leaves a clean and ready to go carb!

 

I totally agree with running it dry. It's been my SOP. However, my Yamaha manual says not to. It recommends a fuel additive and choking the engine off with fogging oil. Just bought a new one last year, so that's what I did. It was hard to restart, since the plugs were soaked. Once it did kick over, it belched out the oil and then ran like a charm again. I'm guesssing the fogging oil might also protect the jets, etc, since you spray it through the carb.

I've also been know to spray a half can of Vavltect Marine Motor De-carb through the running outboard and kill all the bugs within miles. Sit upwind! Not sure it works, but it feels good.

 

The brave mechanics don't use soapy water, they use a propane torch, unlit. When the propane gets sucked into an engine, it creates a richer fuel mixture and you'll hear the engine rpm change. No residue, no contaminants, and only the usual chance of gas vapor explosions.

 

Thanks to all for the suggestions. It gives me some good avenues to pursue.

 

Same problem with SailPro... dirty filter. Same problem with Nissan 4hp ... air leak in tank line. Check both suggestions.

 

Hi,

I have a Tohatsu 6hp Sail Pro Long Shaft.

It starts right up, idles fine but dies after a few seconds once I put it in gear and get underway.

It was running great all last season, and then died on me while underway and hasn't worked properly since.

I cleaned the carburetor and put it in an ultrasonic machine so I don't believe that's an issue.

How would I go about troubleshooting this to determine the problems.

Thanks,
Alan

I have one of those outboards and it has done the exact same thing a few times. Each time changing the fuel filter fixed the problem.

 

A little STP gas treatment is your friend too...

 

Check your fuel line it may be cracked is allowing air to come in and causing it's to stall above idle... I had the same issue on my Tohatsu so I would start with that then maybe look at the carburetor or a fuel tank it could be as simple as not having the air open on the tank

 

Good advice. The typical hose and pressed-on hose connections on the Tohatsu 4, 5 & 6 HP and the remote tanks are NOTORIOUS for loosening, cracking, etc. The tank vent (thumb screw with built in rubber 'mitral valve') is notorious for sticking in the closed position. Most OB repair shops advocate to entirely replace the OEM remote tanks every 3-4 years.
Apparently the 'rubber' used on the OEM fuel supply components and tank systems aren't truly compatible with ethanol-loaded gasoline - hence the rapid cracking, etc.

 

Thanks for your comment. I've gotten several suggestions about the fuel filter including one in the boatyard today. That will be one of my first checks.