I have a Yamaha 25hp 2 stroke that starts and idols great but will only run about half power when running full throttle. It will run full power for about 5 seconds if I squeeze the bulb then bogs back down. I have checked fuel lines and fuel filter. Thanks in advance for the help
Sounds like a plugged main jet to me, I would look into the carbs for sure.
What kind of tank? Those external connections can also develop cracks that will be fine when vacuum is low, but running full will let air in causing stall.
Do you have the mix right? Sounds like the same thing that happened to us when we shorted the oil to save some money dumb idea!!!!!
6 gallon portable fuel tank. I’m going to use a different fuel tank and line tomorrow morning. Hopefully this will solve the problem. I always mix the fuel correctly
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Worth trying the new tank and fuel line before taking apart a carb.
If you do take it apart better off just ordering the rebuild on it beforehand. New gaskets are cheap and easier to not have to line back up the old impressions of carb in old gaskets.
6 gallon portable fuel tank. I’m going to use a different fuel tank and line tomorrow morning. Hopefully this will solve the problem. I always mix the fuel correctly
Yes, try this first. My first thought was a possible air leak in a fuel hose, dip tube, or a leaking fitting, so it’s worth trying a different tank and hose to see if that clears up or isolates the problem.
Check every fuel line under the cowling as well. Pay special attention to any fuel line that looks “wet” or has oil on it. These can be very hard to diagnose if they are leaking so the rule is if they look bad or are wet from possible leaks, replace them.
It could be a clogged main, but I’m not sure this would clear up in the way you describe just by pumping the bulb. Usually a clogged main will result in the engine just dying when full throttle is applied, I suppose it could be partially blocked somehow.
Your symptoms also sound like they could be caused by a weak fuel pump. I don’t know Yamaha’s 2 stroke setup, the old OMCs were very easy to access, Mercs are more difficult to get to and I’ve never done one. This is a very common symptom as you describe it, pumping the bulb will provide fuel pressure to the weak pump to allow it to run for a short period of time.
A few things to check, hopefully you can at least narrow it down.
Grouse
Trying a different fuel tank should tell you, but it sounds like possibly a bad bulb to me. If changing the tank fixes the problem, I would start with replacing the bulb on your fuel tank.
Does the bulb stay pumped up or does it need to be pumped up again to make it run again. Might just be the bulb or line.
The bulb on my last motor would stay pumped up for months. The boat had an internal tank. I pumped it up in the spring and forgot about it the rest of the season.
Thanks for the help. After taking the fuel line of the fuel tank connector, I could see to where the inside liner of the line appeared to be separating. Changed line and problem seems to be fixed
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