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C_Sealover

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Hello all, first time posting so be gentle. I’ve tried to do as much research to resolve the issue but I haven’t had any luck. I have a 20sl with I believe it’s a 24 gallon tank powered by a 2012 Yamaha f70 with 459ish hours. And the problem that I’m having is that I can start the motor and it will idle perfect for how ever long you let it sit. But if you turn it off and go inside for a hour or until the next day all it will do is turn over and won’t fire off. I’ve changed spark plugs, and fuel filter on the motor, and new high pressure fuel pump as suggested by someone. Took it to the sandbar and wouldn’t crank up so disconnected the fuel line at the fuel rail, reconnected and it fired off. Only other thing that hasn’t been changed yet is the primer bulb which gets hard after you pump it 4/5 times and fuel lines
 
Do you have a water/fuel separator?
Do you run Ethanol Free fuel?
 
Yes, I just recently ran all of the fuel out of the tank this last weekend in hopes that it was bad gas. But I had just recently purchased the boat so it was my second time taking it out. First time I took it out was in November when I bought it. Sat in my my shop and finally warmed up enough to take it out and all it would do was turn over unless sprayed starting fluid
 
I am going to assume that when you say “it wouldn’t crank up” you mean the motor will not start when the starter cranks over the motor. The fact that it fired with starter fluid is telling. It could be gas that has lost its volatility. If you recently drained the gas in the tank after draining the gas in the engine fuel rail try draining the gas downstream at the fuel rail again. While you are at it pump out the gas in the fuel line with the squeeze bulb. Keep us informed.
 
If new gas doesn’t fix it, idk what is it could be. It’s just weird that I can get it to crank and idle. But when I turn it off it won’t crank back up but jus turn over
 
DVW said:
I am going to assume that when you say “it wouldn’t crank up” you mean the motor will not start when the starter cranks over the motor. The fact that it fired with starter fluid is telling. It could be gas that has lost its volatility. If you recently drained the gas in the tank after draining the gas in the engine fuel rail try draining the gas downstream at the fuel rail again. While you are at it pump out the gas in the fuel line with the squeeze bulb. Keep us informed.
Click to expand...
 
DVW said:
I am going to assume that when you say “it wouldn’t crank up” you mean the motor will not start when the starter cranks over the motor. The fact that it fired with starter fluid is telling. It could be gas that has lost its volatility. If you recently drained the gas in the tank after draining the gas in the engine fuel rail try draining the gas downstream at the fuel rail again. While you are at it pump out the gas in the fuel line with the squeeze bulb. Keep us informed.
Click to expand...
Also if it was bad gas, wouldn’t it not idle smoothly?
 
I know you said the bulb is firm after 4 or 5 pumps, but is that when it runs fine? When you goto start it and it doesn't fire up, is the bulb still firm? Maybe have somebody squeeze the bulb while your cranking it when it doesn't fire up and see if that helps it start.
 
Your terminology confuses me. The term cranking the motor over means rotating the motor with a external power source in order to ignite the fuel-air mixture that should continue the rotation. The external power source is a battery powered electric starter motor. If the starter rotates the motor initially but it will not continue to rotate (run) when you release the key it is said the motor cranks over but it will not run. Your terminology makes it difficult to understand the symptoms.
 
I seen this many times. Replace your squeeze bulb with a high quality bulb or remove it completely as it’s not really needed in this day and age with 4 stroke engines which you have. If you do replace it, please notice on the bulb the arrows pointing direction of fuel flow.
 
I don't know if this is helpful or not but I used Google Gemini and asked it for potential causes for the engine issue you are having and this is what it said could be your issue...

As Ronald Regan would say "... Trust, but verify..."

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Anything in the fuel system could make it act funny. I'd start with any outstanding maintenance items - VST service done? - so maybe get the service manual and pore over it. Also tank venting issues aren't likely to be your issue but you never know, try unscrewing the fuel filler cap to see if that helps firing it up.
 
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