dirty carb? bad fuel?

Condor1970

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The boat I just bought has been sitting for a year with a full tank of gas to keep the condensation out. However, I don't know if it had some Sta-bil in it or not.

Before we tried to start it, we checked the plugs, wire connections, battery fully charged. When I tried running it, we shot a lot of carb cleaner into the carb, and starting fluid to get it going. The fuel pump is working. I cleaned out the pump filter, and checked the fuel seperator. After trying for about an hour, we gave up for the night, and put the battery on the charger. There is definitely fuel getting to the carb, so we let it sit overnight to let the fuel eat away at whatever might be in the carb. The next day we got it running... sort of. It ran up and down, and responded close to what we would expect. So we shut it down for a few hours, while I worked on other parts of the boat.

Then, when I tried to start it again, it started bogging down on me again. It will not idle, only run sluggish at 1/3 throttle, and when I try to give it gas, I can here the carb sucking in air, but it won't accelerate, and just ends up sputtering and backfiring on ocassion.

I thought it could be bad fuel, varnishing in the carb, but I'm not so sure of that. Usually, even if the fuel is getting old, the engine will at least run, though may not give very good top end performance.... but run, none the less.

Other than pulling the carb and tearing it apart for a full manual cleaning, or perhaps just disconnecting the fuel line and filling it with carb cleaner, what other things do you guys think I should check out beforehand?
 
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Bondo

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Ayuh,..... What motor,..?? What carb,..?? What vintage,..??
 

Condor1970

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Mercruiser 3.0L in a 1989 Regal Medallion 185. Mechanical fuel pump, carburator (don't know which one), and standard round flame arrester. Has a new starter and battery.
 

JerryIrons

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Well if you could hook up a small external tank with fresh fuel you could rule out bad fuel.
 

midcarolina

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Being an 89 it prolly has a points ignition........ if so pull cap rotor and clean, clean or replace points set gap then try again. then if you are sure you have a good strong spark it's prolly time to remove carb disassemble and clean and inspect parts.......or better order rebuild kit for carb
 

UncleWillie

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Collect a sample of the fuel from the tank in a jar.

Fresh gas is clear with a light yellow tint.
If it is Milky/Opaque it has water in it.
If it is a Darker Amber/Brownish/Rusty color it is Oxidized.
If shaking the jar vigorously produces a Foamy "Head" that lasts for more than 5 seconds, the Oxidation has transformed into "Gum".

Diluting the old fuel 1:1 or more with fresh fuel will often resolve the water and Oxidation problems and allow you to run the tank low before refueling again.
 

Condor1970

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Jun 9, 2014
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Being an 89 it prolly has a points ignition........ if so pull cap rotor and clean, clean or replace points set gap then try again. then if you are sure you have a good strong spark it's prolly time to remove carb disassemble and clean and inspect parts.......or better order rebuild kit for carb

It is a points ignition, but the timing is ok, and sparks are strong. Inspected plugs, and color just about right (brownish). I think you're on the right track. I was thinking of just removing the fuel line, and flooding the carb with some cleaner a few times, then seeing what happens. If that won't do it, I can get a rebuild kit pretty cheap for those old carbs I think, and spend a night rebuilding it. If I have to pull it open, I may just take the time to replace most of the parts.
 

Bondo

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Ayuh,..... Attach a remote tank of fresh gas to yer fuel pump, to eliminate eveything Up-stream from there,.....
 
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