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Engine boggs down and dies after 3/4 throttle

N

Navcty850

New member
I have an S175txrv Yamaha oil injected two stroke. Runs great up till a little after mid range. If I throttle higher, it boggs down and will die if I keep it at full throttle. If I back off to mid range, it will pick up and haul butt. I am only able to achieve 3800rpm as of right now.

Carbs are cleaned, fuel lines are good, primer bulb is OEM yamaha and brand new. Fuel pumps are also new. WOT Timing advance is set wide open.
Any help would be appreciated thanks.
 
Last edited:
What does “carbs clean” mean to you?....using carb cleaner?...or pulling carbs and jets, clearing jets, checking float height and needles?
 
Navcty850 said:
I have an S175txrv Yamaha oil injected two stroke. Runs great up till a little after mid range. If I throttle higher, it boggs down and will die if I keep it at full throttle. If I back off to mid range, it will pick up and haul butt. I am only able to achieve 3800rpm as of right now.

Carbs are cleaned, fuel lines are good, primer bulb is OEM yamaha and brand new. Fuel pumps are also new. WOT Timing advance is set wide open.
Any help would be appreciated thanks.
Click to expand...
Sounds like a high speed jet problem or sucking air.
 
newyota said:
Sounds like a high speed jet problem or sucking air.
Click to expand...

I had a similar problem with smaller outboards, turns out the motor was starved for fuel each time. Fuel delivery couldn't keep up at high rpm and once it used up all the reservoir of fuel in the carb bowl it would sputter out and die. When I restarted the motor and kept it at mid-low rpm it ran fine. In one case, there was debris clogging up the fuel outlet port from an internal fuel tank, and another case it was the fuel pickup tube from an external fuel tank. Replacing carbs and fuel pumps did nothing to change the outcome.
 
Couple possibilities here.

Your tank might have some junk in it and your pickup tube is catching it at higher rpm. At low rpm it’s not creating enough suction to grab up all the junk. Higher rpm will create a higher suction clogging the pick up filter.

It also could be the fuel line. Ethanol could have eaten it and at higher rpm it creates enough pressure to bring whatever rubber is hanging in there creating a block in the line.

I had a very similar problem with a Johnson outboard. One of the cylinders wasn’t firing and it would bog down at higher rpm.
 
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