1987 Yamaha 50 hp 2 stroke fuel problem?

[nick jc]

Bought boat 15 yrs. ago, first thing i did was remove all parts associated with oil injection before it went bad and ruined the engine, used it for 2 yrs, ran great with 50:1 mix, parked it for 13 yrs. decided to use it, replaced all fuel lines, bulb, 2 quick connects and water separator, gas tank looked clean and empty, 3 new spk. plgs, started instantly after 13 yrs. ran great with garden hose attached, put in water comes up to 3100 rpm and on a nice plane, 30 seconds later it drops to 2800 rpm, to regain 3100 i have to pump the primer bulb every few seconds, came back and replaced the fuel pump with no improvement, with garden hose attached it runs great with no pumping bulb at 3100 rpms, got any ideas?

 

[mike_i]

Is the fuel vent clear? Besides the water separator are there any other fuel filters? Can you remove the water separator, swirl it around then pour the gas in a glass jar to see if there is crud in the fuel system? Do you have another fuel tank you can run it on?

 

[Sea Rider]

One story is running the motor with no load on muffs, a different one with load on water at throttle past fast idle. What about the motor behaviour at middle to max throttle range, with same issue ?

Have you cleaned all the carb to pristine immaculate condition ? 13 year stop is too much for 2 stroke motors to pretend to run strong as in the good oldie days before the motor stopped being run...

Happy Boating

 

[QBhoy]

Carbs need looked at. I’d also had that usually the oil injection system on these particular motors are excellent.