Tohatsu 4/5/6 B/C and the EPA

[kpgraci]

Found out today that on the Tohatsu 4/5/6 B and maybe C models with carbs that meet the stringent EPA standards and therefore have problems with E10 and other contaminants in the fuel, especially at idle due to an undersized low speed circuit, it is possible to replace the carb with the earlier ‘A’ model version which is less susceptible to this condition. Not advocating intentional by-passing of EPA regs, heaven forbid, but this may be a solution for those tied to E10 (which I am not). Out the box the B/C models run fine, and with proper attention to fuel care and the use of pure gasoline there should be no problems, but it’s nice to know that (for now) this option exists.

 

[Merlin Clark]

Ken,
Thanks for that info.
I had a problem with the "slow jet" (6B) clogging and others here led me to the solution (tiny wire through the end).
I painted the head with a dab of red enamel for easy ID if/when it happens again. The jet is easy to get to on these motors, see below.
But I would rather have the "other" carb.

 

[kpgraci]

You can run a wire through it as a quick fix - the brass slow jet itself and the aluminum carburetor passage associated with it - but you need to be careful not to scratch any surfaces. Minor deformation in the brass jet may cause undesired effects at various RPMs, scratching the anodized aluminum will invite future corrosion and more problems down the road. I've had experts tell me to never use a wire. If solvents don't work then ultrasonic cleaning equipment may work, but the orifice is so small that neither may. It was this very discussion that led to the revelation about using the earlier carb.

 

[Merlin Clark]

The slow jet is like a screw with a hole through it crosswise and a tiny hole drilled through the end to meet the crosswise hole. It has to be removed from the carb (see IDP) to get to the jet end of the screw.
The rest of the carb is completely seperated during the wire poking procedure.
I don't claim to be an expert and so am willing to risk this $7 part.

Edit: I made my response nicer.

 

[kpgraci]

Sure. Just relaying my experience and understanding of the subject. I agree that proper fuel management will prevent any problems and said as much in my post. I bought the motor used and inherited the problem. It may be from E10 (water) or it may be varnish. The problem I have is not with the slow (pilot) jet, but somewhere downline of that in the bypass port or passages leading to the idle port. On this carb the adjustable fuel/air screw is covered over and is illegal to adjust or remove! Behind that needle valve is where my problem lies.

 

[Merlin Clark]

Might check out these guys for a replacement if you decide to go that way. The deal in used outboard and inboard/outboard parts at (IIRC) 1/2 new cost.
http://marinepartsoutlet.com/