1998 Mercury 225 offshore carbureted STARTING PROBLEM

[Zackcole04]

Hi everyone having an issue with my merc starting. Ok i bought this motor used one owner never ay issues he just upgraded motors. Compressions checked out perfectly so i purchased... this is where my problems started, got motor mounted to boat and it fired up perfectly ran it for 15- 20 minutes on mixed fuel. we were waiting on throttle cables to get in for everything wired up new controls fired up fine. we were going fishing one morning the ignition got stuck in the starts position so it kept spinning the starter eventually burning the starter up. Ordered a new starter got it put on now the motor wont start, cranks but wont turn over. We have used a test light in between plugs and top of sparkplug im only getting fire on number 1 and 6 cylinders from wires. dont know where to start with this problem but any help would be much appreciate. thanks in advanced.

 

[Texasmark]

Running high current for an extended period surely drained your battery and could have overheated and damaged your battery to engine connections, both black and red wires. If the engine doesn't spin fast enough to generate adequate spark, a perfectly good engine won't start. If it was running, you had the bad switch problem and now it won't, nothing (seemingly) has changed but possibly needing a new switch, or starting solenoid, and what I said above.

So, if it were mine, I'd find out if it was the ignition switch with an internal short between the ON and Start position....common to have metal transfer from one contact to the other as switches age and short between terminals.....or the starting solenoid could have pitting from age/usage such that the reduced contact area with starting current welds the contacts together and releasing the switch from Start springing back to On DOES remove the control voltage from the switch to the solenoid, but the plunger inside the solenoid stays connected due to the welding.

While that is getting sorted out, I would recharge my battery and have a load test performed (terminal voltage of the battery is checked while the battery is forced to deliver 300 amperes) to see that it is capable of spinning up your engine to the 200ish rpms required for starting.

Then, while things are disconnected in the battery arena, remove the other ends of the battery cables and shine up both ends and reinstall nice and tight.

After you have done that, if the engine, properly primed and throttle at fast idle setting, still won't start, THEN I'd worry about something having changed and a maintenance action would be necessary.

That's the way I would attack your stated problem, knowing nothing but what you told us.

 

[Zackcole04]

Hey TexasMark, I appreciate that I have purchased a new battery for that reason thinking it drained whole that problem happened. Still did not start. I have not checked the wire from battery to motor as of yet so that will be my next step as well as checking amp on leads as well. Thank you for the information i will get to work on it and get back to see if this helped my problem. Thank you sir