Outboard engines pilot jet adjustment

[C08]

Disassembling my Tohatsu 20hp outboard to give the carburettor a long overdue clean out I was surprised not to find a pilot jet adjustment screw and spring. I am not able to compare my carb with the Tohatsu parts list or the Seloc workshop manual as my carb is not detailed for some reason. I cannot see any threaded hole where one could have been and dropped out _ is it common to have this arrangements?

 

[RichardS]

Pilot/idle/slow running jets are often blanked off so it might be behind a plug.

Richard

 

[C08]

It seems that the humble carburetor is now becoming unservicable. As RichardS said the idle mixture screw is behind a blanking plug (IPA Regulations presumably emission stuff). Once upon a time a carburetor had an idle mixture screw and a main jet with an adjustable needle for mixture setting, all very low tech and little to go wrong. My Tohatsu 20HP carb has a large number of holes and pipeways that go who knows where and is not really made to be serviced. I spoke to the outboard dealers close to the boat and he said that apart from floats, float needle valve and gasgets they could not obtain service parts such as butterflys and shafts and that once corrosion had started inside the carb due to water from the Ethanol there was no way of cleaning it out as US cleaning worked well on sticky deposits etc but it would not shift corrosion inside the internal drillings. He said they replaced a lot of carbs on all makes!
The float chamber was clean apart from some fine silt but the breather chamber at the top was quite heavily affected with surface corrosion. The final straw was sheering off 2 screw heads and the inability to drill and tap 5mm screws without workshop facilities meant I ended up buying a new carb. A bit disappointing with a 7 year old engine.