Selva/Yamaha 50hp 4stroke conking out
I recently bought a 4.5m Valiant with a 5 year old 50hp 4 stroke Selva, re badged Yamaha, from a friend of mine, it had been sat in a river and had less than 20 hours use and as far as I can make out had never been opened up as the river has a 8 knot speed limit - I know what I was buying and aware of the history and it was serviced.
I had it serviced again locally and took it out today, I was having a problem with it dieing when I went to engage gear and at a low RPM and it did not sound healthy but when it I gave it some throttle it was fine, it seemed to clear itself so I headed out of Chichester to open it up (had arranged to meet a friend at West Pole just in case of problems).
It was running fine, though seemed a little underpowered for a 50hp on a boat that size, after about 10 mins the problem came back and it would not idle at all and it sounded terrible at low RPM so we towed it back into the harbour, where as before it would come back to life it remained sick every time I tried it, periodically on the trip back to the marina.
I have a warranty from the service and will take it back next week but would love to know what the problem could be.