no power

Just bought a cobia 174 with 90 Yamaha. Put in water fired right up, ran great for 5 min. Then no power. starts right back up and can put in gear, put as soon as I give it gas it goes dead. Restarts right up. Made it to the ramp. Have changed the separator and put a inline filter. Having trouble getting the bad gas out. Has hand pump does not get real firm? Not sure if it is gas.

are you saying you know yo have bad gas?are you saying the bulb never gets hard when you pump it?

that bulb should get hard if the motor is not running...then as you run the boat it is normal for it to not be hard...but you dont want it to try to cave in and try to suck flat...is the tank vent open?

the way the system works is you pump the bulb....that bulb has check valve in it to keep the gas from running back into the tank...when the carbs get enough gas in them they will cut the gas off as the float rises..then the bulb gets hard and should remain hard til you start burning gas...if it dont get hard then this is the first problem you want to address...

Agree with Papyson - check the pump up bulb first. Also, when stalling out, squeeze the bulb several times in quick succession. If engine picks back up, it could be a bad low pressure fuel pump.

Is the Yamaha carbed or fuel injected? If fuel injected, often the culprit is the high pressure fuel filter.