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kjkfender1996@gmail.com
10-05-2011, 05:22 PM
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

haventaclue
10-05-2011, 06:10 PM
I think you need to pull those carbs and clean them again,blow air through them,I believe that once gas is over six weeks,either in to the car or into the chainsaw.Some would say two weeks.:D Do no harm to check your fuel pump.But I think water/dirt in the carbs

guyjg
10-05-2011, 10:36 PM
I put some starbright star-tron the fuel to bring it back to life the gas was about 2.5 years old. Wishfull thinking.

Since the gas already turned to varnish you would get more out of it by adding some red pigment and painting a barn with it. The carbs are full of crap. I agree w/haventaclue.

kjkfender1996@gmail.com
10-05-2011, 10:58 PM
I put some starbright star-tron the fuel to bring it back to life the gas was about 2.5 years old. Wishfull thinking.

Since the gas already turned to varnish you would get more out of it by adding some red pigment and painting a barn with it. The carbs are full of crap. I agree w/haventaclue.

Ya obviously I am not a mechanic and if I had a barn I would take your advice lol. Thanks I will check the Carb again we pulled it apart and checked the filters and they looked good maybe something is obstructing the hoses?? is that seafoam stuff going to help at all or am I wasting my time with that as well.

guyjg
10-05-2011, 11:36 PM
is that seafoam stuff going to help at all or am I wasting my time with that as well.

Canned Seafoam is an additive that dissolves gum and varnish when added to the fuel tank or engine oil. It has been around about 50 years. It also claims to stabilize the fuel. I've been using it for 30 years and have never had a fuel varnish/gum problem in any gas powered device. I add one ounce per gallon to my yard tool gas cans at every fillup. It does not remove dirt from a carb. As I said it dissolves gum/varnish deposits in a fuel system. I had good results recently cleaning a plugged high speed jet in a Merc. carb using the spray Seafoam called Deep Creep.

I would remove your carbs and blow them out. If air does not blow thru each fuel passage then spray some carb cleaner into the plugged openings, let them soak an hour and blow them out again. Repeat as needed or soak the entire carb in cleaner. I like to use lacquer thinner on a neglected carb. It's a fast cleaner but dangerous to use. You need to use a respirator when using it. It needs to be used outdoors because of its toxicity and volatility.

gl115
10-06-2011, 04:21 AM
stabilizers are great to use especially now with the E-10 problems and phase separation,like said above you need to use them at fill up to pro long the gas life, after the fact its 2 late.