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70 yamaha 2 stroke wil not run on plain

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lott1431

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I have 90s 70 yamaha 2stroke, runs great at idle and at half throtle. It will get up and get the boat onto a plain at about 3/4 throtle, but after it runs for about a half mile or so it boggs and the dies. It will start right back up. This spring I had the carbs cleaned out, plugs changed, new empeller installed, compression checked out ok, and changed the oil in the lower unit. what could be causing the problem?
 
Try pumping the primer bulb and if it helps you are looking for a fuel delivery problem. Fuel pump? Fuel pickup tube in your tank might have a screen gathering debris that falls away when the motor stops. ????
 
Hi there. I have a similar problem and was wondering if you ever figured it out. It's frustrating as hell because when it goes, it really goes but then dies out and I have to go through the same old process of restarting and nursing her up to speed again. Anything to help rule it out would be helpful.
Thanks, Greg

p.s pumping the bulb doesn't help and my tank and fuel are new as well as the complete line from the tank to motor
 
My 90HP yamaha 2 stroke did this when I first got my boat. I installed a clear fuel filter between the water separator and the motor and found out there is water coming thru and going into the motor. That's when I decided to suck out all the gas from the tank. Drain the carbs and all the filters and clean the carbs and solved all my running issues. Well not quite until it over heated and shut off the motor too. If it's over heated and shuts off it won't be easy to restart it back up and it should beep constantly. GL
 
Vinh said:
My 90HP yamaha 2 stroke did this when I first got my boat. I installed a clear fuel filter between the water separator and the motor and found out there is water coming thru and going into the motor. That's when I decided to suck out all the gas from the tank. Drain the carbs and all the filters and clean the carbs and solved all my running issues. Well not quite until it over heated and shut off the motor too. If it's over heated and shuts off it won't be easy to restart it back up and it should beep constantly. GL
Click to expand...

Hey, thanks a lot! I spoke to a Yamaha mechanic today and he said the same thing. He said he cleans ALOT of carbs for these motors all summer long. I think I'll start there because I know there's no water in the fuel. I don't think it's overheating because it fires up again right away.

Thanks again, Greg
 
Re: 70 yamaha 2 stroke wil not run on plain-PROBLEM SOLVED!!!!!

I am a happy guy tonight. After having the carbs cleaned and set up, the problem was still there. Today, I had the fuel pump rebuilt with new seals and diaphrams and NOW there is no cutting out at high speed.....just high speed!!!! I have a 16 ft Sunray bowrider that will now do 48 MPH according to my gps.
It was a choppy night but the boat planed out and ran like a charm. If in doubt, either replace or rebuild your fuel pump! :cool:
 
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