Tohatsu 3.5 HP Carburetor part 2

How to clean the carb of a Tohatsu 4 stroke outboard

Remove the carburetor from the engine (see article "Tohatsu 3.5 HP Carburetor").

Turn the carb upside down and unscrew both screws:

Once the screws are out, you to take the carburetor apart by removing the flow chamber:

Use a carburetor cleaner (available at any automotive store) and some cotton tips to remove any deposits. The cleaner I used (Nulon), called for a one-minute soak, followed by a respray to flush off all deposits. I did that, plus I then went after more stubborn deposits with cotton tips soaked in cleaner - it worked well.

A clean carburetor:

If you want to go a step further, you can remove and clean the jets and the main nozzle. Let’s start with the main jet. For this you need a wide flat screwdriver that grips both notches very well. Be careful it's easy to damage the soft brass of the jet.

If the jet is frozen, which seems to happen a lot and is to be expected since two dissimilar metals tend to corrode and bond in the marine environment, you have a few options. However, all of them will most likely result in a damaged main jet. So, make sure you have a replacement ready before you proceed.

Option 1: Clamp the carburetor into a wise, tighten only slightly to not damage the carb, then tap your screwdriver into the jet with a hammer. This did the trick for me and I could unscrew the jet.

Option 2: Use a screw extractor kit with a left hand drill bit and a matching extractor bit. Left hand drills ensure the frozen screw is not tightened in the hole while drilling. Luckily, I didn't need that, but drilling into the jet and then extracting it would have been my second option.

Unscrew the jet, take it out, and hold the carb upside down and tap it a couple of times until the main nozzle comes out. Soak the nozzle with carb cleaner or replace it.

I installed a new main nozzle (3R4-03252-0; 171207) and a new main jet (3AU-04468-0; 171003) from Tohatsu Genuine Parts and Accessories:

Next is the slow air jet, which is used during idling and low speed. It sits on the “right” side of the card (see image). To replace it you need a flat screwdriver with a head just a bid smaller than the diameter of the hole in which the jet is hiding. The screwdriver has to grip both notches (red arrows), otherwise it’s easy to damage the jet.

Replace the slow air jet, or clean it with carb cleaner and then use compressed air to get any gunk out. Do not take an object such as a paper clip and force it through the opening of the slow jet. This will likely enlarge the opening and ruining the jet for good.

Finally assemble the carb again - good luck. Btw, don't forget to tighten the drain screw before you fill the fuel tank ;-)

All the steps above are for my Tohatsu MFS 3.5B outboard engine, but a similar approach might work for other outboards as well. Here is the diagram and the part numbers for this particular carb. The jets and the main nozzle are highlighted in red.

Source www.tohatsu.us

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