Tohatsu MSF 6D Sail Pro

Our Etap is fitted with a 6 HP Tohatsu four stroke outboard engine, ultra long shaft "Sail Pro" edition. The "sail pro" means the propellor is customized towards sailing vessels (higher torque and less speed) and has a through-the-prop exhaust so you stop the boat or go aft.

Owners manual here >>

Service manual here >>

Annual maintenance consists of:

Replace fuel filter (these will fit)
Replace spark plug (NGK DCP 6 RE)
Clean water cooling outlet with wire
Check starter rope for wear
Replace motor oil (450ml 10W-30/40) and washer (part 3H6-07406-0)
Inspect propellor
Replace gear oil (195ml ASAE 80/90) and gasket (part 332-60006-1)
Replace impellor (part 369-6501-1)
Inspect anode and replace if >50% has worn
Grease points as per manual

July, 2023 - Engine troubles continues

The engine still suddenly shuts down occasionally, although the behavior is different now. The shutdowns only occur when the engine is hot, and when it is set back to idle or just above idle after a prolonger period under load. Unlike the previous issues due to a failing primer bulb, there is no audible cue before the engine shuts down. Also, the RPM seems to fluctuate a bit during normal operation, going up and down ever so slightly.

What I've tried so far:

Ensure the tank vent is open
Replaced fuel filter and spark plug
Adjusted the idle screw, it now runs close to 1300 RPM in idle!
Cleaned the carburetor

Update August 2023:

After some googling I suspected the fuel pump may be the culprit. I've order a new one of AliExpress which does NOT fit!. Even though the part number listed is the same one (3H6-04000-7M), in fact the screw hole is slightly padded such that it will NOT be possible to mount the fuel pump flush to the cam shaft/block, which in turn prevents the fuel pump from pumping any fuel.

I wrote a post in a sailing forum which responses suggested I try the following (which I will do soon):

Clean the carburetor again with high-grade carb cleaner
Pierce the mainjet and regulator with copper wire
Remove the fuel cab (in case the air valve is not working)
Have the whole carburetor cleaned ultrasonic (will try this one if all the above fails)

... I'll keep you posted...

April, 2023 - Engine stalls

The engine would suddenly stop after 10-15 minutes of operations. When under load, the RPMs would suddenly decrease just before shutting down. The engine would not restart before priming the pumping ball again. Also, I noticed that if you'd start pumping immediately after the RPMs would fell, it wouldn't shut down (for another 10-15 minutes).

Replacing the fuel lines and primer bulb seemed to do the trick.... I think.