New Tohatsu 3.5 BS will not go in gear, will not accelerate

ruukee

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Aug 15, 2011
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My 3.5BS was purchased and tank tested four months ago. Last month, I tried it on my boat. When I place it gear, it usually dies. If it does not die, then when I accelerate, it will die.
I brought to the service center and they told me it was bad gas. After dip cleaning the carb, replacing the fuel and adding an additive to the fuel and charging me $110, they tank tested it without the propeller. It went into gear, but lagged or bogged down when accelerating. The technician told me that it was having problems at "transition" and the fuel additive would help it to work better over time. If it does not improve, I could bring it back and they will replace the carb for $125 plus labor.

With the prop on, I have the same problem as before the repair. I have discovered that if I'm able to sneak it in gear and keep it running, I can then move the throttle quickly from idle to faster, idle, then faster, idle, faster, etc. about 6 to 12 times, it will eventually take and run fine at higher speeds. If I go back to idle, I will often need to re-massage (idle, fast, idle fast...) it into the higher speed.

What's wrong? Do carburators need to be replaced if fuel has sat in them for 4 months? There must be something else. Is it the throttle control?
Rob
 

pvanv

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Apr 20, 2008
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Re: New Tohatsu 3.5 BS will not go in gear, will not accelerate

It's clear from your description that your low-speed carb passages are still fouled. Idle and transition issues is typical of that problem. If not too bad, it's sometimes possible that running at transition, with super-solvent additives may help some, over time, but we have never had much success trying that. A second trip to the dip tank may fix that, and IMHO, the shop should at least attempt that, because they did not fix the initial problem.

You can not effectively tank test with the prop off, as you are not loading the motor. The carb for the MFS3.5B is 3GV032000M, $141.82, so they are discounting it pretty aggressively for you. Yes, anything over a week with fuel left in the carb can/will indeed varnish up the narrow passages in the carb. You must run the carb dry, religiously, at the end of each and every day. If there was water in the fuel, the problem could be oxidation (microscopic white aluminum "rust") in the passages, which cannot be cleaned by ordinary methods -- and if so, a new carb is required.
 

Silmaril1067

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Aug 16, 2011
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Re: New Tohatsu 3.5 BS will not go in gear, will not accelerate

I had the same problem. I took off the carb and really hit it with spay carb cleaner. Worked fine. And like Pvanv said, run it dry every time.
 

Sea Rider

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Sep 20, 2008
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Re: New Tohatsu 3.5 BS will not go in gear, will not accelerate

Check tank's fuel **** filter for internal obstructions that limits fuel delivery to carb, clean carb as recommended.

Happy Boating
 

pvanv

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Re: New Tohatsu 3.5 BS will not go in gear, will not accelerate

On the B model, the fuel strainer filter is remote from the tank... integral with the fuel ****... difficult to reinstall, to say the least.
 

ruukee

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Aug 15, 2011
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Re: New Tohatsu 3.5 BS will not go in gear, will not accelerate

Thanks. I'll try to figure out if I can do anything with the fuel strainer. If it is difficult to re-install, I'm not certain I want to get into it.

The repair shop was unwilling for a second trip to the dip tank because it was in there for 6 hours for it's first bath and he felt that any longer would begin to destroy some of the necessary components. Also, fuel began leaking around the gas cap when the motor was tilted forward on the mount. I could not figure out the problem with the cap, but as I kept working with it, I discovered that the plastic gas tank was cracked around the threaded opening. So, I was told that is not under warranty and I had to buy a new $50 gas tank for my new Tohatsu. Perhaps the cracked gas tank alllowed water into my carb.

The repair shop again drained the fuel, put in new, and demonstrated that it works fine - as long as I hold the choke part way out while accelerating through transition and then pushing the choke in.

I sure hope I don't need to use this in an emergency situation - by the time I get it warmed up, sneak it into gear and then do the choke-dance through transition, it will be too late.

Another person told me that if I buy ethonal free fuel, I will greatly reduce the problem of fuel going stale in the tank and varnishing the carb within a week. Is this true?
Rob.
 

pvanv

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Re: New Tohatsu 3.5 BS will not go in gear, will not accelerate

You need to see a different dealer.

The tank should be covered under warranty, unless you cross-threaded the cap or wrenched it down super-tight.

While the carb issue may have been caused by contaminated fuel, or letting fuel stand in the carb, either way, it needs the carb working right. Either a better cleaning, or a new carb. Asking an owner to trick the choke to accelerate is Unacceptable.

Presence of alcohol in the fuel does not make it go stale faster, nor does it contribute to varnishing. There are other issues associated with ethanol (such as phase separation) which you will not experience as long as you follow the rules... and run the carb dry every day, and only run fresh fuel.
 
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