No power

[retfire02]

I have an 04 yamaha 115 four stroke that has been sitting for about six months. When I took it out to just run it recently, it wouldn't power up! I tried changing the fuel filter and water seperarator filter to no avail. My son is an automobile mechanic and he pinched off the return line from the fuel pressure regulator. The engine immediately powered up with the muffs on. He thinks the pressure regulator is bad. A friend who is an outboard mechanic said I probably just need to drain the fuel/water from the tank (no easy task) and it should be alright, but the injectors may need cleaning. The Yamaha dealer said they have never seen a fuel pressure regulator go bad. On subsequent checking, the water seperator filter did not seem to have any water in it. The boat had less than half a tank when I first tried it. After it wouldn't power up I went and filled it up which may have been a mistake? Any suggestions?

[99yam40]

yes 6 month old fuel can be a problem and all you did was add some to it which could mean all of it is bad now

[glfolts@gmail.com]

New fuel might be the easiest place to start but it is also pretty straight forward to test your High Pressure fuel rail to see if you are holding pressure. There is a Scharder valve (like a bicycle tire air valve) on top of the fuel rail. I think Yamaha specs 42 # (Seloc says 35-42#) of pressure, mine is currently running at about 40. The pressure regulator will dump off excess pressure and is generally vacuum operated. If it is failing and causing the performance issue, you should see low pressure or pressure falling off under load.

Most auto stores will have the HPFP test gauge with adapters for various size valves. Mine cost about $14 at harbor freight.

I tried to attach the specs from the 03 service manual. They should be close, but you probably should verify. In any case, you should see it dropping if there are any issues with,vent, fuel lines, filters, low pressure pump, HPFP, or regulator. Most will starve the VST tank of fuel.

Cheers