2014 Yam 50hp knocking

[redsinthehead]

Starts strong, runs for an hour or so at different speeds, usually from a low idle it will act like it’s starving for fuel, squeeze the bulb and rpms come back up, get up on plane it sometimes hiccups a little but there is serious knocking sound from front of motor. Fuel is good, tried two different tanks and lines... oil pump? Sensor? Not running hot... doesn’t go into limp mode... water pump peeing strong and cold?? Any ideas?

[99yam40]

F50?
if pumping bulb makes a difference, I would be checking on the fuel pump
knocking ,running so lean getting preignition maybe

I would be checking fuel pressure at the rail and to the VST
if pressure stays in spec then test & clean injectors

[rejesterd]

If the rpms increase when you pump the bulb, you need to inspect the mechanical fuel pump. Also check the fuel filter cup for any solid bits that might be floating around.

I would not focus on the knocking.. instead, focus on the fuel starvation symptoms, and then see how the knocking is after resolving the fuel issue.

[redsinthehead]

Had my mechanic go through the VST, he checked all fuel lines, fuel pump... (I actually replaced it) said all looked good???? If I pump the bulb before every run, stay at high RPMs ... runs fine, if I don’t pump the bulb, run high rpms then drop to a low idle For a few minutes ... it starts knocking and chokes down... bulb almost empty... pump bulb, knocking quiets down and runs ok... I was told possible vapor lock from fuel heat exchanger being plugged?

[TownsendsFJR1300]

Built in fuel tank or remote?

If built in, try running the engine directly to a 3 or 6 gallon vented tank...


If your engine has a fuel cooler, it's easy enough to check if it's clogged. Two lines in, two out. One has water, so that /part of the cooler should not be clogged...