Tohatsu MFS3.5B idling problem

[Catalina36]

"ran great (apart from idle) for 5 minutes then suddenly died."

When you replaced the tank, did you also replace the cap? I had this problem years ago, ran for five minutes then died and it took me far too long to realise that the tank breather in the cap was blocked.

 

[Jamie Dundee]

"ran great (apart from idle) for 5 minutes then suddenly died."

When you replaced the tank, did you also replace the cap? I had this problem years ago, ran for five minutes then died and it took me far too long to realise that the tank breather in the cap was blocked.

Tank came with a new cap. I also unscrewed the cap to check that the fuel was flowing properly. Had I realised the carb had been played with I wouldn’t have bought the engine. Too late now but at least it’s now running properly and I know the impeller and gear oil have been done correctly.

 

[bluerm166]

For anyone else who has doubts about their carb float level and has no measurement instructions about how to check or reset it by ,if necessary,bending the tab ,I suggest they take a look at this video which demonstrates the very simple clear tube method of seeing the actual fuel level .

The demonstration starts around 6.30 and applies to any carb.
Whilst I have the precise manual instruction for setting the height of the 3.5A carb this is no help at all on the 3.5B carb ,because the float is different, so I used the method to make progress.

 

[Stemar]

An off the wall idea: I had a Tohatsu 3.5 2T which had classic symptoms of fuel starvation - not the same as yours, but typical carb issue. After stripping the carb twice, a sharp eared friend heard a ticking noise, which turned out to be sparking at the earth connection of the coil. I remade the connection to the block and no more "fuel starvation".

 

[Jamie Dundee]

An off the wall idea: I had a Tohatsu 3.5 2T which had classic symptoms of fuel starvation - not the same as yours, but typical carb issue. After stripping the carb twice, a sharp eared friend heard a ticking noise, which turned out to be sparking at the earth connection of the coil. I remade the connection to the block and no more "fuel starvation".

I did wonder about an electrical fault but seeing the state of the carb installation suggested a carb problem, confirmed by the results from the new carb.