92 Yamaha 115 fuel problem

[atomictow]

My outboard will run fine for about 5 minutes. Then it will bogg and surge at full throttle. I had my buddy pump the bulb and the problem disappeared. I changed the fuel pump and cleaned the carburaters but the problem still exists. Any ideas?

[Ken]

Check the vent on your fuel tank - may be clogged/crimped and a vacuum is forming.
Try momentarily loosening the fuel filler cap when the motor boggs and then pump primer bulb and see if rpms pick back up and stay there.
Also, if you have an anti-siphon valve on the fuel line, they are bad about sticking and not allowing fuel flow at the higher rates.
Good luck [img]smile.gif[/img] ,
Ken K

[atomictow]

the vent is clear and I replaced both quick connections for the fuel line. No luck. I have a couple of ski-doos and when the shaft seal started leaking I had a similar problem but the engine would not idle. The outboard idles with no problem and low RPM is stable. What would cause the pump's pulse to weaken?

[Ken]

atomictow,
Try using a separate (6 gallon) fuel tank and primer bulb to see if that makes any difference.
Also, did you use a new gasket between the new fuel pump and engine block?
Ken K [img]smile.gif[/img]

[jb123]

choke each carb throat with your finger, listen for the rpm change and find out which carb is still clogged.
also, your motor is over 10 yrs old so i would visually check each fuel hose, from tank to carbs as you could also have an air leak.

[atomictow]

There is a new gasket and the bolts are tourqed properly. When I had the caburators off I checked the fuel lines and they are clear. They were replaced last year. I'll try choking each carb. I'll let you know what happens. Thanks for all the help.

[slim]

how old is the boat? some boat builders install a filter in the fuel pickup in the tank. try using a 6 gallon tank. if the problem goes away and you have looked at your fuel lines good, then it may be in the tank.

[atomictow]

The tank is new and there is no filter inline. However I will be installing a filter / water sep. after this problem is solved. I hooked up the fuel line directly to the filter on the engine, bypassing the quick connect. The engine no longer surges but at full throttle it will lose RPM and stay there. That to me means the fuel is not getting low enough in the bowls to cause a severe drop in RPM. I figured that the fuel is keeping up better. I am going to remove the fitting from the tank side and see what happens.

[atomictow]

My problem may be solved. When I purchaced the engine second hand I was not given the big oil supply tank that mounts in the boat. I installed it and it has been running fine, full RPM. Has anyone experienced this problem before?

[jb123]

save yourself a headache or 3 and rid of those quick disconnects in your fuel lines and i doubt much that pumping your ball had anything to do with your non-installed oil tank.