Yamaha 4hp revs

[Portland Billy]

I have a Yam 4hp on an inflatable tender which has run well all season - until now!
It revs OK when not under load, but when in gear stalls if I exceed dead slow revs.
Any ideas?

 

[neale]

How old is the fuel? Current fuel seems to have the shelf life of a bottle of milk. My first action when faced with any outboard related problem is to try fresh fuel. Seems to cure the problem more times than not.

 

[john_q]

I had a similar but not identical problem, I knew my fuel was OK as I use the O/B every day.

The engine would start OK, rev OK out of gear but fail under load (but not always immediately). The local Yamaha dealer in Rio Dulce eventually diagnosed a bad main jet (he had a spare carb to play with), problem solved and jet cost about £5.00. The engine has never started so well!!

He said that the jets can wear quickly due to the "bad" quality of fuel htese days and also water/condensation in the fuel

 

[landlockedpirate]

When was it last serviced ? How old is the fuel ? Is there anything wrapped round the prop ?

Fishing line could stall the engine in the circumstances you mention.

 

[Lakesailor]

Just clean the carb and pay attention to the main jet as that is, as said, the symptom you describe. Use an air line if possible to blow it out.
It may be worth putting a fresh plug in first.

 

[Fantasie 19]

Just clean the carb and pay attention to the main jet as that is, as said, the symptom you describe. Use an air line if possible to blow it out.
It may be worth putting a fresh plug in first.

Praise where praise is due - I'm a mechanical numpty and couldn't figure out why changing the plug would make a difference but having not fixed the outboard stopping issue with a carb clean, I remembered this post and changed the plug for the spare I carry - looks to have fixed the issue.. cheers Lakey..