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  #61  
Old 08-01-2012
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Re: tohatsu 3.5 won't run without choking

Quote:
Originally Posted by Sapperwhite View Post
Seloc Marine has a book on about every engine out there.
Agreed, Seloc has a way with words to help you understand your motor. I would recommend it over any others.

If choking it keeps it running it does sound starved for fuel. Float valve can stick or stuff can block flow even if the float and valve operate correctly. I had a head gasket leaking water into the combustion chamber on a 2 HP older motor and with choke on it would at least run. The evidence was in removing the spark plug and shining light on the piston to observe tiny droplets on the piston. Very little water, but gasoline will generally not leave this evidence so I replaced head gasket. The gasket gave me even better indication where the leak was.

Lastly, if the float or valve were not filling the carb bowl with gas due to sticking would expect a shot of starting fluid while it falters would bring up the rpm as the fuel shortage would be remedied and the intake path wouldn't be blocked. Hope this helps and let us know what you find.
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  #62  
Old 08-02-2012
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Re: tohatsu 3.5 won't run without choking

You did not adequately clean the carb. Carb spray itself it not aggressive enough to dissolve the organic varnishing in the low-speed passages. You must completely disassemble it (including jets, emulsion tube nozzle, and of course the needle and float). Then submerge in real carb dip for 4 hours at room temperature. THEN blow it out with generic carb spray, and reassemble, paying close attention to the float height.

You did not need to adjust the pilot mixture screw. But, since you did... It should not bottom out the spring; it should Gently seat in a delicate brass jet in the carb. The correct initial setting is about 1-3/4 turn out, and once the motor is running OK and fully warmed, you would then adjust it as on any other carb on any other motor. If you are not familiar with that procedure, or don't have a very good ear and a razor-accurate shop tach, get assistance from someone who does. Yes, you must pull the fuel tank bolts to make that adjustment... But since you are "never" supposed to change it, that's not a big deal.

There is in fact an inline filter screen between the fuel **** and the tank, which should be inspected.

HTH
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  #63  
Old 08-02-2012
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Re: tohatsu 3.5 won't run without choking

Quote:
Originally Posted by Sea Dawg View Post
Agreed, Seloc has a way with words to help you understand your motor. I would recommend it over any others.
The Factory service manual (either the Tohatsu or Mercury) is head-and-shoulders above the Seloc, generic, one-manual-fits-all, publication. For one thing, it explains how to disassemble the carb, which so far has not been done.
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Old 08-03-2012
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tohatsu 3.5 won't run without choking

I have a Tohatsu 3.5 as well. I have an intermittent problem driving me nuts. Most of the time it starts reasonably easily. Once started it runs fine But once in a while it is dead as a door nail. Yes the fuel **** is open, the fuel tank vent is open, the starter kill switch is in place the choke is pulled. I am inclined to think it is electrical, but have been unsuccessful in finding the problem. Any suggestions?
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  #65  
Old 08-04-2012
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Re: tohatsu 3.5 won't run without choking

You open the manual and start running the tests on the ignition system or you can randomly replace parts hoping that the shotgun approach will yield a positive result.
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