Tohatsu 3.5 HP Carburetor part 2


Carb II pic00 tohatsu 3.5 carburetor 150x

Opening and cleaning the carburetor out of a Tohatsu 3.5 HP outboard 4 stroke

A clogged carburetor can be easily taken apart, cleaned, and re-assembled. Here I will also clean/replace the main jet, the main nozzle, and the slow air jet. 

How to clean the carb of a Tohatsu 4 stroke outboard

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

Carb II pic01 tohatsu 3.5 carburetor assembly

 

Turn the carb upside down and unscrew both screws:

Carb II pic02 tohatsu 3.5 carburetor float chamber screws

 

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

Carb II pic03 tohatsu 3.5 carburetor float chamber removed

 

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.

Carb II pic04 tohatsu 3.5 carburetor cleaner

A clean carburetor:

Carb II pic05 tohatsu 3.5 carburetor clean

 

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.

Carb II pic06 tohatsu 3.5 carburetor main 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.

Carb II pic07 tohatsu 3.5 carburetor main jet free

 

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.

Carb II pic08 tohatsu 3.5 carburetor main jet nozzle

 

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:

Carb II pic09 tohatsu 3.5 carburetor main jet nozzle 3R4 03252 0

 

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.

Carb II pic10 tohatsu 3.5 carburetor slow 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.

Carb II pic11 tohatsu 3.5 carburetor slow jet free

 

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

 Carb II pic12 tohatsu 3.5 carburetor reassembly

 

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.

Tohatsu MFS3.5B carburetor diagram parts

 

ic. Ref.

Part Description

Tohatsu
Part Number

Original
Part Number

Remarks

(1)

INTAKE MANIFOLD

3BRB020910

3BRB02091-0

 

(2)

INTAKE MANIFOLD GASKET

3AB021040M

3AB-02104-0

 

(3)

BOLT

9101F45630M

9101F4-5630

 

(4)

CARBURETOR ASSY

3GV032000M

3BR-03200-0

3.5PS / MARK: 3GVA

(5)

MAIN NOZZLE

3R4032520M

3R4-03252-0

3.5PS

(6)

MAIN JET #68

3AU044680M

3AU-04468-0

3.5PS

(7)

SLOW AIR JET (#115)

3GT049150M

3GT-04915-0

2/3.5PS

(8)

FLOAT

3GT032310M

3GT-03231-0

 

(9)

FLOAT VALVE

3H6032400M

3H6-03240-0

 

(10)

CLIP

3H6032440M

3H6-03244-0

 

(11)

FLOAT ARM PIN

3H6032320M

3H6-03232-0

 

(12)

FLOAT CHAMBER

3GT032210M

3GT-03221-0

 

(13)

FLOAT CHAMBER GASKET

3H6032220M

3H6-03222-0

 

(14)

SCREW

9225036412M

922503-6412

 

(15)

DRAIN SCREW

3H6032920M

3H6-03292-0

 

(16)

DRAIN SCREW O-RING

3H6032930M

3H6-03293-0

 

(17)

STOP SCREW

3AB032650M

3AB-03265-0

 

(18)

STOP SCREW SPRING

3H6032670M

3H6-03267-0

 

(19)

RUBBER CAP

3GT032560M

3GT-03256-0

 

(20)

PILOT SCREW

3AB032660M

3AB-03266-0

2/3.5PS

(21)

CARBURETOR GASKET

3H6020110M

3H6-02011-0

 

(22)

INSULATOR

3H6039521M

3H6-03952-1

 

(23)

INTAKE SILENCER

3H6024110M

3H6-02411-0

 

(24)

FLAME ARRESTER

3H6026030M

3H6-02603-0

 

(25)

COLLAR 6.2-9-7.4

3A0760790M

3A0-76079-0

 

(26)

COLLAR 6.2-9-7

3H6760791M

3A0-76079-0

 

(27)

BOLT

9161F10685M

9161F1-0685

 

(28)

WASHER

9401030600M

940103-0600

 

(29)

CABLE HOLDER

3H6635050M

3H6-63505-0

 

(30)

BOLT

9101030616M

910113-0616

 

(31)

NUT

9301030600M

930113-0600

 

(32)

RUBBER HOSE

98AB30230M

98AB-3-0230

98AB-301000

(33)

BREATHER HOSE

3AB074350M

3AB-07435-0

 

Source www.tohatsu.us

 

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