JimC Posted February 10, 2021 Share Posted February 10, 2021 Hi all. I am having a problem with my 30hp Yahama outboard. The problem is that is seems to starve for fuel. Idles fine and runs ok up to about 6 knots then starts to lose power erratically. A quick pump of the bulb and it is right again. Fuel is clean, new hose and primer bulb fitted and used screw clamps on all joints. Engine filter is clean. New fuel pump kit fitted..gaskets and diaphragm. I am now scratching my head as to where to go next. Sounds like it is sucking air in but I cannot find where. Any suggestions?Jim Link to comment Share on other sites More sharing options...
noelm Posted February 10, 2021 Share Posted February 10, 2021 There's a bit at play here, first off, if the tank is not vented, the fuel primer bulb will "suck flat" pumping the primer kind of takes the fuel pump out of the system, you said you replaced the pump, was it a new, genuine pump, or a cheap after market one? do you feel confident doing the carbs yourself? they are not hard, and only require basic tools, but they need to be done right, not sprayed with cleaner or washed, but, properly cleaned. Link to comment Share on other sites More sharing options...
frankS Posted February 10, 2021 Share Posted February 10, 2021 I'm with Dave here, make sure the tank is vented, probably a small knob on fuel filler that needs to be opened. A mate had a similar problem and it turned out that the actual plastic tank was dissolving and particles of plastic were blocking the fuel line. Never heard of that before and I can only assume he was using ethanol in the fuel . DO YOU ?. Frank Link to comment Share on other sites More sharing options...
JimC Posted February 10, 2021 Author Share Posted February 10, 2021 Tank vent is open and not blocked. Tank pickup is clean and fuel flows freely. However I might have just fixed the problem. I only use unleaded, not E10. Apparently there is no fuel pump available, only gasket and diaphragm kits. However there are two one way valves. These are a tensioned metal strip and they open and close as required to allow fuel to flow in but not back. One of the valves appeared to not be closing properly so I readjusted the tension and now the motor is holding high speed idle without starving. Incidentally the on-line handbook says to replace the fuel pump every two years but it seems the complete pump is not available. Time will tell. 1 Link to comment Share on other sites More sharing options...
noelm Posted February 10, 2021 Share Posted February 10, 2021 Not too sure about replacing the pump every couple of years, but anyway, as I said, pumping the primer bulb kind of bypasses the fuel pump. Link to comment Share on other sites More sharing options...
dunc333 Posted February 11, 2021 Share Posted February 11, 2021 well done jim c let us know after 10 hours run time she is all good cheers dunc333 Link to comment Share on other sites More sharing options...
Hoods Posted February 11, 2021 Share Posted February 11, 2021 Check all fuel hoses and connections from the tabk to the fuel pump etc - sounds like air is getting in somewhere Link to comment Share on other sites More sharing options...
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