Air/Fuel Mix??

Islandlure

Seaman
Joined
May 14, 2006
Messages
63
I have a 1988 30hp Yamaha pushing a 16' aluminum jon boat. Recently the primer ball has started to collapse at full throttle pinching off my fuel to the motor, but it only does this at full throttle. About 10 seconds before it kills the fuel flow the boat really starts moving it really does feel like a boost of nitrous. Now I am wondering if the motor is getting too much gas and is bogging down. If I could get it to run liek it does for that 10 seconds before it dies, it would be awesome. Any Suggestions. Thanks :)
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: Air/Fuel Mix??

what you have is a restriction between the primer and the liquid in the tank, what your noticing is the added power of a very lean fuel mix. what the results will be is burned pistons.
 

Islandlure

Seaman
Joined
May 14, 2006
Messages
63
Re: Air/Fuel Mix??

The manual says mix at 100:1. Should I make a richer mixture? And it also sounds like I just need to replace all the fuel line and primer ball.
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: Air/Fuel Mix??

oil/fuel and air/fuel dont have much in common.<br /> do ya know anything aboutgas welding and gas cutting ?<br /> sounds like ya need to do some inspecting/testing before replacing.
 

Islandlure

Seaman
Joined
May 14, 2006
Messages
63
Re: Air/Fuel Mix??

Okay thanks, I thought that my problem might have something to do too much fuel or too much air into the carb. But I will play around and see what I can figure out. Thanks again.
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: Air/Fuel Mix??

dude<br /> I am in a foul mood tonight.<br /> you do have an air/fuel mix issue.<br /> its called way to much air for the amount of fuelin the combustion chamber.<br /> I am gonna bust your chops but if ya listen I will make you teach yourself.<br />if ya play to much yopu WILL damage a piston.<br /> the difference between gas welding and gas cutting is basically the amount of oxygen(air) used for heat or melt.<br /> most portable tanks have a screen in the draw tube.<br /> check carefully for anything that will restrict fuel from the draw tube to the primer bulb.<br /> as your bulb is sucking flat it indicates something is restricted from the outlet of the bulb to the liquid level in the tank.<br /> the pump is trying to suck something. it cannot. so the bulb sucks shut.<br /> think of it as you sucking a coke through a crazy straw, the vacum only appears at the restriction.<br /> the relation of vacum to air pressure is difficult to visualize. next time you stick a straw in a coke think about it.<br /> the air pressure on the liquid in the glass and the lip end of the straw is equal.<br /> when you suck on it its not the suction of your lungs moving the liquid but the airpressure on the coke that places that refreshing beverage in your mouth.
 
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