Possible carb issue with Merc/Tohatsu 9.9?

WN2712NJ

Seaman
Joined
Jul 17, 2010
Messages
65
Hi-

I am posting this here rather than in the Merc forum because I know the OB in question is really a Tohatsu powerhead. It's a 2006 Mercury 9.9 4 stroke. It's been stored most of the last 3 years and I recently pulled it out of storage because we plan on selling it. The engine was "run dry" and fogged before storage.

The good news is that it started right up. Seems to idle fine. However, if I rev the engine up even a little bit, after 10 or 15 seconds it will suddenly die. If I then try to restart, a normal restart doesn't work. What does work is to open the throttle all the way (flooded start procedure). It will then start and idle. However, as soon as try to rev up it again dies. There is visual evidence of gas in the exhaust when this happens.

I'm trying to get a handle on what the likely problem is, and what it might cost to fix. From the symptoms, I guessing some type of carb or fuel pump issue, for example a carb float that is stuck, causing it to run way to rich on the main jet.

Anyway, I'd welcome input from Tohatsu Guru or anyone else on the forum.

Thanks

-dm
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Re: Possible carb issue with Merc/Tohatsu 9.9?

Soak carb properly in real carb dip to start with. Carb must be inmaculate clean for engine to perform best at all throttle ranges.

Happy Boating
 

TOHATSU GURU

Admiral
Joined
Jul 22, 2004
Messages
6,164
Re: Possible carb issue with Merc/Tohatsu 9.9?

Ditto...Take the carb apart, remove the rubbers and soak in carb cleaner for at least three hours.
 

WN2712NJ

Seaman
Joined
Jul 17, 2010
Messages
65
Re: Possible carb issue with Merc/Tohatsu 9.9?

Ditto...Take the carb apart, remove the rubbers and soak in carb cleaner for at least three hours.

I just had an interesting phone call with the local Merc dealer. He claims that my problem is probably due to running the carb dry before storing the motor! This runs contrary to all the advice I've ever gotten on this forum.

What do you guys think?

Thanks

-dm
 

TOHATSU GURU

Admiral
Joined
Jul 22, 2004
Messages
6,164
Re: Possible carb issue with Merc/Tohatsu 9.9?

Think about it for a minute. If the carb is dry it would be impossible for it to cause a problem. There are a variety of people who are now in the marine industry who do not have a clue about basic mechanics, fuel system troubleshooting or have any sense at all. Always run the engine dry. And the way to do that is as follows:

Run the engine at an idle until the engine starts to run rough.

Then pull the choke out and shove it back in.

Repeat until you have to keep the choke pulled out for it to run.

When the engine finally dies the true death you have emptied the carb of all but two or three drops of fuel.

Or

You can simply open the drain screw on the bottom of the carb and avoid running it dry.

The theory about not running the fuel dry is based on the FALSE premise that the fuel system is a closed loop. It is not. Over time the fuel in the system will eventually evaporate leaving the sticky residue that causes the clogged jets and stuck needles. Usually the same people that tell you to leave the fuel in the carb will tell you to add a fuel stabilizer...As if that had anything to do with the problem. Stabilizer keeps the fuel from rotting (remember the fuel is biological and does go bad) but does nothing to prevent the evaporation that causes 99% of carb issues.

Side note*

I have a few friends who have a different opinion than mine on this issue. Some are very bright, some are very experienced and all are very wrong:) There are also people who never run their carbs dry and "have never have problem"....It's like running a red light. You might get away with it a hundred times, but one day...You will come to an abrupt stop.
 

pvanv

Admiral
Joined
Apr 20, 2008
Messages
6,500
Re: Possible carb issue with Merc/Tohatsu 9.9?

I need to have this framed and hang it in my shop. Well said, Elvin !

Think about it for a minute. If the carb is dry it would be impossible for it to cause a problem. There are a variety of people who are now in the marine industry who do not have a clue about basic mechanics, fuel system troubleshooting or have any sense at all. Always run the engine dry. And the way to do that is as follows:

Run the engine at an idle until the engine starts to run rough.

Then pull the choke out and shove it back in.

Repeat until you have to keep the choke pulled out for it to run.

When the engine finally dies the true death you have emptied the carb of all but two or three drops of fuel.

Or

You can simply open the drain screw on the bottom of the carb and avoid running it dry.

The theory about not running the fuel dry is based on the FALSE premise that the fuel system is a closed loop. It is not. Over time the fuel in the system will eventually evaporate leaving the sticky residue that causes the clogged jets and stuck needles. Usually the same people that tell you to leave the fuel in the carb will tell you to add a fuel stabilizer...As if that had anything to do with the problem. Stabilizer keeps the fuel from rotting (remember the fuel is biological and does go bad) but does nothing to prevent the evaporation that causes 99% of carb issues.

Side note*

I have a few friends who have a different opinion than mine on this issue. Some are very bright, some are very experienced and all are very wrong:) There are also people who never run their carbs dry and "have never have problem"....It's like running a red light. You might get away with it a hundred times, but one day...You will come to an abrupt stop.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Re: Possible carb issue with Merc/Tohatsu 9.9?

Will add, once engine starts to die of fuel starvation, pull choke out and back in while throttling from idle to fast idle, repeat untill engine drops dead. Runing carb dry is a must do if wanting to count with an inmaculate clean carb, the soul of the party.

Happy Boating
 
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