I'll post some more pics later, but this will give you a start.
The Yamaha two-stroke-power-cycle outboard engines have several items considered maintenance besides spark plugs. First, there is inspection and cleaning of the vapor separator tank filter and the vapor separator tank. Second is replacement of the low-pressure fuel pumps.
The VST fuel pump filter is a pricey plastic screen that snaps on to the bottom of the fuel pump. The tank can get muddied up apparently from use, clogging the screen.
The low pressure pumps have a diaphragm inside that can fail.
My engine would run fine at speed, but after idle speed running the engine quit. Two bulb squeezes and it started right up, no problem for a couple of hours then a repeat. Again, two squeezes and fine until I was idling up to the first of four bridges I have to transit.
Two things I noticed wre the the prime bulb would not get hard, and, when I was doing this in my driveway, I found a yucky oily mess coming out of the prop hub along with raw gasoline.
The VST tank and filter and the low pressure pumps have a user-group recommendation of just changing out the pumps and cleaning the tank and filter every three seasons.
The VST tanks needs an O-ring replaced. There are three bolts, two medium pressure fuel lines, a few other rubber hoses, and two wires; and the tank is off.
A bunch of screws and the tank is separated.
The fuel filter twists off the bottom of the pump.
NOTE; the fuel line pressure first has to be bled down, and the non-reusable fuel line clamps are not a standard PEX clamp--although they look close in size.
Figure [on performing the above procedure] along with three-year service of the thermostat and poppet valve.
[LINKS to part sources]
Gasket =
http://www.simyamaha.com/Yamaha_Vapor_Seperator_Float_Chamber_Gasket_p/66k-14984-00-00.htmFilter element =
http://www.simyamaha.com/Yamaha_Fuel_Filter_Element_p/65l-24563-00-00set.htmEngine mounted low pressure pump KIT =
http://www.simyamaha.com/Yamaha_Fuel_Pump_Assembly_p/6e5-24410-03-00kit.htmPressure fuel line clamps =
http://www.simyamaha.com/Yamaha_Fuel_Hose_Clamp_p/65l-24387-00-00.htmExpensive plastic fuel pump filter (cleanable) =
http://www.simyamaha.com/Yamaha_Fuel_Pump_Filter_p/66k-13915-00-00.htmAnother item if you have the old, prone to breakage plastic trim lever =
http://www.simyamaha.com/Yamaha_Cam_Trim_Sender_Kit_p/99999-03830-00.htmVapor separator tank or VST
VST pump filter with some debris. I used Brakleen and a parts cleaning brush with plastic bristles.
Low pressure fuel pumps
Failed pump diaphragm
This is about a 1 hour repair.