Tohahatsu 4hp MFS4

[builderbill]

I am new to this forum so please excusse me in advance of any misstakes. I have a carb problem, When I hook up a fuel tank and prime the bulb gas pours out of the carb at the top and will not stop until I disconnect it. What possably could be the cause? The engine also does not run smooth.

 

[TOHATSU GURU]

Re: Tohahatsu 4hp MFS4

It has a dirty carburetor. Take it to a dealer and have it cleaned.

 

[pvanv]

Re: Tohahatsu 4hp MFS4

Yep. The needle isn't seating correctly.

 

[builderbill]

Re: Tohahatsu 4hp MFS4

Thanks for the advise. I forgot to mention the motor has only a couple hours on it. I used a gas additive and it did set for a couple of months without use. I am also interested in the info on upping the HP to 6. If the carb is changed out do you also replace the prop with a differant one?

 

[Sea Rider]

Re: Tohahatsu 4hp MFS4

The prop must be same for both models, you should run carb dry after each outing to avoid oil gum formation inside carb specially when stopping an engine for so long.

Happy Boating

 

[pvanv]

Re: Tohahatsu 4hp MFS4

The carb is 3R4032001M, CARBURETOR ASSY, MFS/NSF6A2, $110.97, available from any dealer, including me. You must run the carb dry at the end of each and every day, or risk gunking the carb up again.

You can run a variety of props depending on your needs. In most cases start with the original prop and see how that works; If needed, then install a different pitch.

 

[builderbill]

Re: Tohahatsu 4hp MFS4

Thanks to all that replied. Yep! I took the carb apart and sure enough, float and needle where stuck. I will drain it after ea. use. Gummy gas. I guess Stabul is not all it claims to be? Back to the 6HP carb, how could 50% more HP transfer to the same prop without over revving the engine?

 

[pvanv]

Re: Tohahatsu 4hp MFS4

Odds are that your carb still needs a proper soak cleaning. The passages involved are microscopic compared with the needle and fuel inlet. Stabilizer helps the shelf life of gas by slowing spoiling; It does not prevent gunking varnish residue that is left after evaporation.

The same prop may well be OK. On-board testing is the only definitive way to determine the best prop pitch. Check the specs for the prop that comes standard on the 6 hp; the standard props are 7" - 9" pitch. Not a huge difference unless way under-powered with a very heavy load. For an analogy, a pickup truck can come equipped with either a 6 cylinder or a hemi, yet run the same tires and rear end.