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Replaced all fuel lines and filters replaced plugs. Engine ran fantastic after short warm up idles beautifully with idle control not engaged. I ran one tank of gas and had no problems ran fantastic then ran a second tank which may have had bad gas in it. I put some starbright star-tron the fuel to bring it back to life the gas was about 2.5 years old. Ran it for a bit even opened it up for a short run brought it in and it started cutting out and wouldn't idle. I actually had to use my trolling motor to bring the boat in because it wouldn't stay running. I replaced the plugs again filled both tanks with new gas and and put some seafoam in it, Checked the fuel filters they were good and took it back down to the launch to test it. Same issue it just won't go to full idle it started getting a little better as I ran it but then when I went to idle it it wouldn't idle, Typically cold I'll start the motor run it on full idle for about a minute and then I never have to touch the idle again it just runs great. I am stuck I have no idea what else to check any suggestions would be great.
Could it be a Fuel Pump Diaphragm??
Mercury 500
SN#4142853
think its a 1979
Could it be a Fuel Pump Diaphragm??
Mercury 500
SN#4142853
think its a 1979
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