Mercury 7.5 1982 Starting problem

[Light air]

The motor came with my Catalina 22 of the same year - probably the original motor. When we went to launch the boat after buying it, the motor (electric start) did nothing. Turns out the ground wire from the battery was pulled out of its terminal. Quick fix. There was also a wire that was grounded to the motor that was running loose and no idea where it belongs, but the motor turned over and ran anyway. A few days later I was out to the boat and started the motor - perfect. 2 days later, this past Friday, all that would happen was that the starter would engage but nothing else. It was getting fuel.
I changed the top plug but lost the new lower one in the water. The old plugs seemed to be OK so I reused them.
Long story short, why would the motor run then 2 days later not run. The loose wire could be part of the shorting system. We are in the middle of a snow storm so no going out to the boat for a week or so. I was going to start by changing the plugs again then trying to check out the shorting system. I have no other ideas.

 

[Tom J]

There are a couple of possibilities. Most likely, if you used ethanol gas, it probably ate up the varnish in the fuel tank and deposited it in the carburetor. Also, if the loose wire was part of the engine shut off, it might be touching the chassis somewhere. Did the engine kill switch work normally when it was running?

 

[Rich Stidger]

And if the small wire was part of the battery charging circuit, maybe your battery is too low to start?

 

[Stu Jackson]

Do you have a manual for the engine?

 

[Light air]

OK,
1. Gas is fresh, tank is new
2. Loose wire is definitely a ground and I made sure it was not touching anything.
3. Battery is new and fully charged
4. I got the manual off line and there is nothing in there that can help.
A friend suggested that the starter is spinning but the solenoid is not engaging the flywheel - suggested I tap it with a hammer to unstick it.

 

[Stu Jackson]

Loose wire is definitely a ground and I made sure it was not touching anything.

Why? Should it not be connected appropriately to complete a circuit?

 

[Light air]

Why? Should it not be connected appropriately to complete a circuit?

Yes but the motor ran without it. I'm thinking it is part of the shorting circuit. I just couldn't see where it was attached to.

 

[JoeWhite]

Is the gear in neutral? There is a switch on it that prevents it from starting unless it is in neutral.

 

[Light air]

Tripple checked and it was in neutral. If it wasn't, the starter wouldn't have engaged.

 

[Rich Stidger]

Back to basics- If the starter is spinning, will it start on a squirt of starting fluid? If yes, then the problem is not likely to be ignition and most likely to be fuel.
Your first post stated that it was getting fuel. How did you determine that? And can you confirm that it is still getting fuel? For instance, are the plugs wet?

 

[Light air]

It didn't start with a squirt of starting fluid which led me to believe that it wasn't a fuel problem but an electrical one. When I pulled the plugs, they were wet. I am leaning toward either the shorting system or a stuck solenoid in the starter. I won't know for at least a week when the weather improves and I can get out to the boat.

 

[Rich Stidger]

The service manual should show all of the wiring and the operations that can stop the engine. I would disconnect the engine stop circuits from the ignition system. Maybe a failed stop switch? Does the ignition system require 12v to energize? Every run and stop criteria needs to be verified. Make no assumptions.

 

[Light air]

I don't have a service manual, just the owner's manual and it doesn't show any wiring systems, but I agree that I should be looking at the stop switch. Google sent me to a site that says I should try disconnecting the black/yellow wire first and/or the black/white wire from the stop switch. I still have to figure out where that loose ground wire goes.

The starter spins up but I don't think it is engaging the flywheel. That is the other system I will be looking at.

 

[Rich Stidger]

If you are certain that the flywheel is not spinning with the starter, I would look at that issue first. Everything with fuel and ignition could be fine but obviously if the engine isn't turned over, it is not going to start. If the starter will run in gear you can watch the prop to see if the engine is turning over.

I assume that you don't have a manual pull rope?

 

[Light air]

No manual pull rope. There is writing on the side of the starter motor that says Do Not Hit (or something to that effect). Don't know how else to see if it's stuck unless I tap it

 

[rgranger]

Don't know how else to see if it's stuck unless I tap it

LOL

 

[Light air]

I called Mercury's classic motor helpline. Great people. They are telling me that it sounds like the gear on top of the starter may be worn out and is not engaging the flywheel. It is shimmed and it's possible that a shim shifted or fell out and that is an easy fix, other than that I will have to have it rebuilt. I can't get to the boat for at least a week so everything waits till then.

 

[jibes138]

Most small motors with electric start have an emergency pull cord option to start. See if you can turn it over by hand with a pull cord to start it. Also with the cowling removed you should be able to see if the flywheel is turning when you activate the starter? Finally, I haven't seen that you checked for a spark at the plugs? Pull a plug and with insulated pliers hold it against a screw on the motor or other ground point to see if you have a spark, if the motor won't turn over this won't work so check that first.

 

[Light air]

Unfortunately, there is no pull start to this motor, there may have been at one time but no longer. With the cowl off, I can see the starter Bendix spin but not raise high enough to engage the flywheel. I already checked the spark plugs and, as a precaution, changed them - there is a spark.

 

[twalker H260]

It would be unusual in that size motor not to have some sort of emergency rope pull start arrangement. Maybe photos of looking down at top of motor with cowl and flywheel cover removed would help see if some provision is there?