timsailing
New member
Hi all and thanks for reading this. I have a Yamaha F9.9 4 stroke 2017 outboard motor that has been running sweet until recently it started losing power. It has always been serviced at Yamaha. The motor has under 100 hours. I am a retired car mechanic. It starts fine and idles well but now will not get to full power or on the plane. It does not miss or sputter just has low power and not teaching full revs under load. The hull is clean, the propeller is free, I have changed the plugs, checked compressions, changed the fuel filter, removed and cleaned the carburettor that was very clean inside, checked the oil level and changed the fuel, checked the connections are fitting correctly. The timing belt looks fine and has the correct tension. The warning light works on starting and is not coming on when running. I have primed the hand fuel primer whilst running to check the fuel pump is working OK. I have searched the internet with no results other that the below video that looks like the same symptoms. To me it’s like the timing has moved or changed electronically. Can anyone suggest anything? Thanks. Tim
Yamaha 15 Hp Four Stroke outboard still no power under load - YouTube
Yamaha 15 Hp Four Stroke outboard still no power under load - YouTube