Fuel Starvation

[Bug]

89 90hp, 2-stroke motor, the motor only runs at 20kts, at full throttle. Seems like it is starving for fuel. We have checked the fuel vent, fuel filter looks fine..of course we can't tell if the problem is getting fixed until we put it in the water.

Any other easy suggestions before out next trial run would be appreciated.

Thanks

[Hamfisted]

Can you pump up the primer ball firm? If not check the fuel pump. How old is the fuel pump anyway? If it's more than 5 years old I'd change it. Have the carbs ever been rebuilt? If the motor is allowed to sit up for more than a month with fuel in the carbs it will turn to glue and clog up everything in the carb. You can try pulling the main jets out and spraying some Amsoil Power Foam or Berryman's Chemtool spray (Walmart) up in the fuel bowls to flush 'em out but they may be too clogged up and require a tear-down. Do you have a service manual for the motor? If not you can go to www.Yamahapubs.com and order one for about $60.


Mike

[Ken]

Bug,
Yeah - what Mike says.
I'm assuming that 20kts is a lot less than you normally run at WOT.
Get the boat up to top speed and have someone check the primer bulb. If it has collapsed, then there is a restriction from there on back to the fuel tank. Could be kinked fuel hose, or tank not venting properly, or faulty anti-siphon valve if you have one on that tank.
If the bulb has not collapsed, then try pumping it several times - if rpm comes up, then you have a faulty fuel pump. If rpm does not come up, then carbs are probably clogged up.
What about spark plugs? If more than a year old, I would put in new ones.
Good luck [img]smile.gif[/img] ,
Ken K