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Yamaha F100 bogs down after running perfect

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Buddy Row

New member
Off the trailer, my Yamaha F100 will crank perfect, run smooth at full throttle, and idle perfect through the "no wake zone", but when I get back on the throttle it will run smooth only to about 3000 rpm's. When I go to full throttle it objects and sputters and will not rev up. It then seems to rev up OK in neutral but will not under load.
Thanks in advance for suggestions.
 
Buddy Row said:
Off the trailer, my Yamaha F100 will crank perfect, run smooth at full throttle, and idle perfect through the "no wake zone", but when I get back on the throttle it will run smooth only to about 3000 rpm's. When I go to full throttle it objects and sputters and will not rev up. It then seems to rev up OK in neutral but will not under load.
Thanks in advance for suggestions.
Click to expand...

What year is the engine? 2-stroke or 4 stroke? Carbureted or Electronic Fuel Injected? Built-in or external fuel tank and gal size? Old stale gas? Ethanol blended gas? Have you been adding any fuel stabilizers and what kind? Have you checked all fuel filters, checked for water in filters, and tightened of all fuel connections? Pulled fuel line from under the cowling and confirmed pumping the squeeze ball delivers a strong, easy flow/squirt out of that line? Have you pulled the fuel pick-up line that runs to the bottom of the fuel tank and checked if there is a small filter on the end of it? If there is - pull it off or cut it off and DO NOT REPLACE IT OR TRY TO CLEAN IT. Sounds like a fuel issue to me - stale ethanol gas, water in gas, poor flow, gummed up filters or fuel jets due to ethanol, sucking air due to a lose fuel line connection/fitting somewhere, or a clogged fuel pick up line filter in the that cloggs after running for a while and then magically unclogs after a shut down with debris falling off and floating back into the tank before udner load again and it clogs again.

High reving under no load requires minimal fuel - under load is when the engine is really trying to suck fuel from the tank and push it into the cylinders.
 
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Try squeezing primer bulb while underway after 3000 rpms and see what happens,if all good fuel pump or fuel delivery problem is your possible issue. keep us posted.
 
Buddy Row said:
Off the trailer, my Yamaha F100 will crank perfect, run smooth at full throttle, and idle perfect through the "no wake zone", but when I get back on the throttle it will run smooth only to about 3000 rpm's. When I go to full throttle it objects and sputters and will not rev up. It then seems to rev up OK in neutral but will not under load.
Thanks in advance for suggestions.
Click to expand...

Did you ever solve this issue? having the exact same problem in my carbed F100.
 
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