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2005 Mercury 25/20 jet missing

RiverBlazer

New member
So I've got a 2005 Mercury 25/20 jet where to me it is running on one cylinder at idle or low speed then when I give it a little throttle it is like I flip a switch and the second cylinder kicks in and runs perfect all the way to full throttle. It has always ran perfect and started very easy before this issue. I always run the gas out every time. I run non ethanol gas and put a little star tron in the tank as well. It doesn't sit for more than a couple of weeks, fish in winter as well. I called a boat dealer and told the mechanic what was going on and he mentioned checking the pilot jet, I took the carb off and apart and the only jet I saw was the one inside the float bowl drain screw which I thought was the main jet. Anyways there was no dirt inside. To me I'm thinking a coil is going bad or maybe the cdi box. Anybody had this issue or can somebody give me some advise on what you think. Thanks in advance.
 
The easiest thing to do, since this issue is occurring at low rpms is to simply put a timing light on each spark plug wire and see if they are both firing. That will either confirm or deny an ignition issue.

If you "don't have spark" or erratic spark then you know the next step is to trouble shoot the electrical system.

If it's "fine" then perhaps you have a fuel issue and can trouble shoot that.

Outboard parts are too expensive to simply "swap and hope" - process of elimination must be followed unless you light your fireplace with $100 bills :)
 
The easiest thing to do, since this issue is occurring at low rpms is to simply put a timing light on each spark plug wire and see if they are both firing. That will either confirm or deny an ignition issue.

If you "don't have spark" or erratic spark then you know the next step is to trouble shoot the electrical system.

If it's "fine" then perhaps you have a fuel issue and can trouble shoot that.

Outboard parts are too expensive to simply "swap and hope" - process of elimination must be followed unless you light your fireplace with $100 bills :)


Thanks for the information! I will plan to run it this weekend and see what happens with the timing light.

Yes I agree, the parts are expensive and I don't want to guess.
 
Thanks for the information! I will plan to run it this weekend and see what happens with the timing light.

Yes I agree, the parts are expensive and I don't want to guess.

It's hard to go to the river and work on your engine when there are fish to be caught anyways I put my rods down and diagnosed my problem before it left me stranded, it turned out to be the cdi switch box. I ordered the CDI Electronics brand, runs like new.
Thanks
 
Thanks for the update. Far too many open/unresolved threads on the net. Good on you for using E-free with stabilizer. You may never have any fuel problems at all for the life of that motor if you keep that up!
 
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