1999 15 hp yamaha fuel problem

fisherman47

Cadet
Joined
Sep 25, 2009
Messages
10
I just put a new diaphram in the carb. The engine idles great, but will not take the gas fast but will take it if you turn throttle slowly. If running about 1500 rpms for about 30 seconds engine will cut off like it is out of gas, but will start right back up. Could it be a clogged carb or fuel pump? any advice
would be greatly appreciated.
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
7,596
Re: 1999 15 hp yamaha fuel problem

The diaphragm you replaced was it the only part you replaced? There are more than one in that fuel pump.
Sounds like the pump is not getting enough the fuel into carb or you have plugging in the carb. Pull the carb and clean out all passages
 

fisherman47

Cadet
Joined
Sep 25, 2009
Messages
10
Re: 1999 15 hp yamaha fuel problem

The only diaphram I replaced was the one in the carburetor. The motor was running great until the diaphram started leaking at the bottom of the carb. I also forgot to mention that the motor is a 4 stroke.
 

ENSIGN

Lieutenant Junior Grade
Joined
Jun 21, 2009
Messages
1,179
Re: 1999 15 hp yamaha fuel problem

These carbs can be very fussy! The passages and jets are very small and the only way to get them right is a complete rebuild,disassemble and soak all metal parts in carb cleaner for a day and blow ALL passages out with compressed air. This is not the time to take shortcuts!!! Installing a water seperating filter between the engine and primer bulb would be a good idea.
 

fisherman47

Cadet
Joined
Sep 25, 2009
Messages
10
Re: 1999 15 hp yamaha fuel problem

I disassembled the carb to clean it and it looked ok inside. I went ahead and checked all holes and cleaned it. Put it back together and it still would not take the gas and would cut off. So I decided to reajust the air mixture screw. It was backed out 3 turns so I backed it out 1/2 turn at a time to 4 1/2 turns, it takes the gas now and does not cut off. I haven't tried it in the lake yet, but I think I will probably have do a little fine tuning. Is it normal to have the air adjustment backed out to 4 1/2 turns?
 

ENSIGN

Lieutenant Junior Grade
Joined
Jun 21, 2009
Messages
1,179
Re: 1999 15 hp yamaha fuel problem

Four stroke carbs run lean from the start.(You can thank the EPA) I really can't tell you the exact number of turns on the mixture screw,there all different.Just make sure you have CLEAN fuel,put the boat in the water and run and adjust the carb.
 

fisherman47

Cadet
Joined
Sep 25, 2009
Messages
10
Re: 1999 15 hp yamaha fuel problem

Thanks for the reply. I realy appreciate the info. Hope you have a great day.
 
Top