Outboard won't run after sitting for the winter

pekstrom

Chief Petty Officer
Joined
Dec 31, 2015
Messages
490
Hi everyone,

I have a 1980 Mercury 25HP outboard with electric start and remote controls. I have posted about this outboard before, but last year I managed to get it to run good thanks to some good advice here. Well, last fall I decided to follow the manual's procedure for running it dry for the winter.

Since the weather has finally cooperated this weekend I decided to get it running so we could go to the lake for a bit. It started ok, but only ran for a few seconds and then acted as if it didn't get any gas. If I primed it, it would start again but die a few moments later. I noticed that the cup for the fuel filter was about half full before it ran, and after it had run, the cup was full. If I pumped the prime bulb the level in the cup went down. One thing I didn't try was to pump the bulb while the engine was running. Based on how it was behaving though I would think it would have kept running as long as I kept pumping. Since there isn't much in between the connection for the fuel line and the carburetor, I'm leaning towards something with the fuel pump. It doesn't seem like it pulls gas from the tank like it should. Would y'all agree with that as a place to start? The pump is basically a thin rubber membrane in the carburetor so I'm wondering if I have a tear in it or something.

How do y'all winterize smaller engines like this one? Would it be ok to leave ethanol-free gas with stabilizer in it over the winter?
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
Did you remember to open the vent on the gas tank?

When you ran the carb dry, what did you do with the remaining gas in the tank and the fuel line? Did you add a stabilizer to the gas before running the engine for the last time?

Fogging an engine while running on Stabilized Fuel, then shutting it off. is the procedure usually recommended in owners manuals. I guess a fussy person could drain the carb.
 

pekstrom

Chief Petty Officer
Joined
Dec 31, 2015
Messages
490
Did you remember to open the vent on the gas tank?

When you ran the carb dry, what did you do with the remaining gas in the tank and the fuel line? Did you add a stabilizer to the gas before running the engine for the last time?

Fogging an engine while running on Stabilized Fuel, then shutting it off. is the procedure usually recommended in owners manuals. I guess a fussy person could drain the carb.

I did catch the tank vent, so it was open when I tried. The first time it was closed. But it didn't seem to make much difference.
Hmm, now that you mention it, I don't think I had any stabilizer in the tank. That would probably have been a good idea. The manual basically just said to start it, disconnect the fuel line and let it run dry.
 

JDusza

Ensign
Joined
Apr 21, 2009
Messages
934
Sounds like carburetors but want to rule out spark first. Check spark with an air gap spark tester. Do try running and squeezing the fuel ball. Are the carburetors getting fuel?
Fuel pump is a quick test. Remove fuel line between fuel pump and carburetor and turn the engine over. Fuel should squirt out of the fuel pump. Use a rag and wrap the fuel pump outlet so fuel doesn't go flying everywhere.
J
 

pekstrom

Chief Petty Officer
Joined
Dec 31, 2015
Messages
490
Sounds like carburetors but want to rule out spark first. Check spark with an air gap spark tester. Do try running and squeezing the fuel ball. Are the carburetors getting fuel?
Fuel pump is a quick test. Remove fuel line between fuel pump and carburetor and turn the engine over. Fuel should squirt out of the fuel pump. Use a rag and wrap the fuel pump outlet so fuel doesn't go flying everywhere.
J

I do believe the spark is ok but till test it to be sure. I'll do the squeeze test while the engine runs as well. On this engine the fuel pump is part of the carburetor so I can't remove the fuel line. If I keep squeezing the bulb on the fuel line though, eventually fuel comes out of the carburetor. I have a gasket kit for the carburetor on its way. Thankfully they still seem easy to find for these older engines. I did a complete cleaning and gasket replacement of it last year and was hoping to not have to do it again this year. We'll see. Thanks for the tips and and advice so far!

1980-Merc-Carb.png
This is the diagram over the carburetor. The fuel pump are the parts in the lower half, that attaches to the left side of the carb.
 

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pekstrom

Chief Petty Officer
Joined
Dec 31, 2015
Messages
490
Alright, today I finally had some time to look at this again. Sure enough it ran better if I pumped the bulb but I couldn't keep it running. I did notice gas leaking out from the fuel pump cover though. So off the carburetor came. What did I find when I took the fuel pump cover off? Well, a dried up and shrunk cork gasket!

1980_Mercury_25hp_Fuel_Pump_Gasket.jpg

I inspected the rest of the fuel pump but everything looked great. As I mentioned earlier, I did a complete cleaning of this thing last year. I put a new cork gasket in place. Closed it back up and tightened everything properly. After putting everything back, the engine ran great! And with the electric choke working now, it was much easier to start than before. So we'll take her to the lake later today for a test ride.

Thanks for the tips and advice everyone!
 
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