I have a new 2019 4 stroke Yamaha 6 hp outboard, with less than 10 hours the motor overheated. Brought it back to the dealer and he replaced the impeller and thermostat. Motor starts up fine, but will only run for a short time, if I watch the fuel filter as it empties below 50% the motor shuts down, if I keep pumping the bulb from the external tank I can fill the filter and keep the motor running. On the internal tank it will stayed full a it longer but will also empty out and shut down. I suspect its the fuel pump, however the dealer wants $300 to replace with no guarantee it would be covered under warranty as it might be covered under warrant. All the usual tests such as checking fittings, different fuel lines, checking gas in carb, arrows right way, pick up in fuel tank, have been checked.
It should be possible to test the pump for proper function - there should be no need to replace it hoping for a cure.
A fuel pump should suck at one end and blow at the other and this can be measured using appropriate gauges and if those measurements are satisfactory the amount of fuel pumped can be measured...
Such tests are fairly routine on wheeled vehicles and not only are they a valuable aid to correct diagnosis they remove all doubt when warranty work is involved.
Testimonial: "Thank you, it seems the dealer should have been able to test the fuel pump prior to telling to replace it."
SOURCE: 40hp 1987 yamaha outboard motor will run for 30-60
Sound like the fuel pump is not keeping up with the engine's demand. Check it out. Good luck. Hope this helps.
SOURCE: 6hp Johnson outboard stalls & quits
go to an auto parts store and get a can of gasoline additive called seafoam. Read the label so you know how much to add to your 6 gallon tank. This stuff works wonders on outboard motors.
SOURCE: 4 stroke 6hp mercury outboard -brand new first
????? Was the dealer using his fuel tank or yours.Might be a blockage or contaminate in the fuel tank.Hope this helps
SOURCE: Filling my gas tank the pump keeps shutting off
Its a fact the pump will kick off on some makes especially trucks. here is a hint. When filling up insert the nozzle fully and then pull it back one inch. This way it will not stop or splash back at you which some pumps do
SOURCE: i have 30 hp two stroke pull start yamaha outboard
yam water pumps are clever the offste centre causes the pump vanes to flex during rotation and at low RPM you have a displacement type pump, at high RPM water pressure forces the vanes to flex inwards and the pump becomes centrifugal, you can fit the impellar either way up so you cant fit it wrongly make sure your gaskets are ok and that the delivery pipe to the power haed is not leaking (try a hose on it) also make sure the little woodruff key or on some models the pin through the drive shaft which turns the pump is fitted ok, not much else that can be wrong!
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Hi Buddy, did you ever get to the bottom of this? I have exactly the same symptoms after over heating my Yamaha 6HP and the dealer replaced the impeller and thermostat. Now it only runs for any length of time on the external tank and I need to keep the bulb primed otherwise it cuts out.
FYI for my issue it was the fuel pump. The overheating had seized it and the engine was cutting out once it had used the primed fuel. I bought and replaced the pump myself (took ages to get the part) and it is now working well.
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