Mecury 1984 25hp doesnt start

[venture_out]

I have a 1984 Mercury 25hp that started and ran fine, except I did notice that I had to pump the bulb a few times while running at full throttle because it started to slow down. After pumping the bulb, the motor sped back up, and appeared to run fine. After stopping for a short bit, the motor would not start back up again. After pulling out the plugs and drying them off, it appears that there is no spark coming from either plug. I'm not sure if the motor slowing down a bit during full throttle and the spark plugs having no spark are related. Any ideas would be great. Thanks.

 

[TommyA]

Re: Mecury 1984 25hp doesnt start

How are you determining the plugs aren't firing? The problem with pumping the fuel bulb to keep the engine running is the fuel pump isn't working or there is a small hole in the fuel line allowing air in the line. The engine flooded and wet the plugs. Wet plugs will not fire so after drying them did you check for fire then?

 

[venture_out]

Re: Mecury 1984 25hp doesnt start

After I got back home, I pulled the plugs, dried them off, connected them back to the wires but did not re-install them. I then pulled the starter cord to turn the engine over while looking for a spark on both plugs. There was no spark present on either plug.

 

[TommyA]

Re: Mecury 1984 25hp doesnt start

The plug will need to make contact to metal somewhere on the engine to complete the circuit. Not knowing your mechanical ability I'm not trying to be a smart A.Make sure that the metal on the spark plug is touching the metal on the engine. From what you have said so far I really don't believe that you have a spark problem but we can't rule it out. Try wedging it in a way that you still can see the gap and if possible in a dark area.

 

[venture_out]

Re: Mercury 1984 25hp doesnt start

Re: Mercury 1984 25hp doesnt start

Thanks for the response, I understand, and I didn't take it that way. Yes, I did make contact with the cylinder head to complete the circuit, and there was no spark from either plug.

 

[TommyA]

Re: Mecury 1984 25hp doesnt start

OK then we have two problems now. First to solve would be the no spark one. I would do a search to see if there are any other threads here that will help to trouble shoot your ignition system. I am still learning and with my unfamiliarity of your specific engine I would not want to steer you wrong. Fuel pump rebuild kits are usually inexpensive and are a good thing do so I would plan on rebuilding it along with what ever is causing the no spark.

 

[8075mercury]

Re: Mecury 1984 25hp doesnt start

Agree with above and some additional thoughts:
*Get a Seloc (I like Seloc) and or Mercury service manual off ebay or direct. Photos and info are invaluable !
*I made up set of alligator clips/wire for plugs to ground. Works better and better than guessing if you have a good ground for the plugs.
*Got to have a healthy spark and clean carbs/working fuel pump to operate properly.

Good luck as these are great motors and were in the Mercury lineup for a very long time!

 

[venture_out]

Re: Mecury 1984 25hp doesnt start

Thank you very much for your responses. I agree that I most likely have 2 different things going on. It's been a very dependable motor that I've had for around 20yrs now. I'll start working with your suggestions. I like the idea of the alligator clips for the spark plugs. Good ideas.