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1999 Yamaha F25 bogging down

A

Aussie Steve

New member
Hi all,

I have 1999 F25 (4 stroke), when I first launch I never have any problems, after trolling and idling for 20-30 minutes it bogs down and spatters when I try accelerate.

If turn the engine off for 30 seconds and then restart, it then runs at 100%.

I have replaced carburator, fuel pump, spark plugs, fuel filter and fuel line including prime bulb (everything new)

Had fuel tank cleaned and breather works.

Stumped as to what it could be?

Any advice would be appreciated.

Thanks
 
Hi mate, that’s actually a fairly common issue on the older F25 four strokes. Since you’ve already replaced most of the fuel system (carb, pump, lines, filter etc.), it sounds like the engine may be leaning out after long periods of trolling.

One thing to check is the carb float height. If the float level is slightly too low, the engine will idle fine but when you try to accelerate the bowl can’t refill fast enough and it will bog. Turning the engine off for 30 seconds allows the bowl to refill, which is why it runs perfectly again after restarting.

Another possibility is fuel vapour/heat soak after long idle periods. When it happens again, try squeezing the primer bulb while accelerating. If it immediately improves, then it’s definitely a fuel supply issue (float level, fuel restriction, or vapour lock).

Also worth checking the tank vent again and the thermostat, as overheating at idle can sometimes contribute to this behaviour.
 
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