Merc. chugs but won't run?

[philtheskipper]

1979 Mercrusier 120hp, 153cid, serial #5474115<br /><br />First off let me say that the engine ran perfect all year. Today I go out to winterize it and it won't start. It'll turn over but stalls out instantly. I checked the spark and spark plugs, all good. Took the flame arrester off and when I pump the gas the carb is getting it. Also tried the old starter fluid but didn't help. What should I do next?<br /><br />I don't have much time before the freezing weather. Would it hurt to winterize the engine without running it?

 

[C17LoadSmasher]

Re: Merc. chugs but won't run?

Fresh fuel might do the trick, depending on how old what's in the tank is, of course. Does it crank well - good speed, etc? Maybe the battery's a bit on the weak side if the boat sat for some weeks. Just some thoughts...

 

[geriksen]

Re: Merc. chugs but won't run?

does it have good spark?<br />does it start but die as soon as you let off the key?<br />have you tried cleaning off the points?<br />Ideally it would be good to run it to get fuel stabilizer into the carb. <br />Try scraping the points with some 800 grit sandpaper then clean them with brake cleaner to get it running<br />then replace them in the spring before using the boat

 

[philtheskipper]

Re: Merc. chugs but won't run?

Guess it could have bad gas. The last time I used it was 3 weeks ago.<br /><br />It's cranking good, battery is fine.<br /><br />The points were replaced with a petronix electronic module. I have good spark.<br /><br />It starts for a second but then shuts off. Does stall as soon as I let the key off.<br /><br />At the beginning of this mess I got the engine to run about a minute but it stalled and now it won't run.

 

[philtheskipper]

Re: Merc. chugs but won't run?

Could it be the fuel filter? Maybe it isn't getting good gas flow when I'm not pumping the gas?

 

[C17LoadSmasher]

Re: Merc. chugs but won't run?

Have someone else pump some gas a little to it while you start it. When they stop, see if that's it. Could be fuel filter.

 

[geriksen]

Re: Merc. chugs but won't run?

If it quits right as you let the key off follow the purple wire all the way from the ign switch to the coil. Or turn the key on an check to see if you have at least 9 volts at the coil. If you don't you have lost the ign ciruit from the key switch. When you crank the engine this cicuit is bypassed and it wull run as long as you hold the switch in the start position. As soon as you release it and power must come from the purple wire it will quit. This is tricky since if you are checking for spark while cranking it will show that you have spark. Try turning the the key to "on" and see if there is power at the + on the coil. Or, you can just jump 12volt to it and see if it runs then.

 

[philtheskipper]

Re: Merc. chugs but won't run?

Thanks for the help. I'll check the fuel filter and the coil tomorrow and post what happens.

 

[philtheskipper]

Re: Merc. chugs but won't run?

gerikson,<br /><br />You were right! The coil isn't getting enough voltage. It's getting about 4 with the ignition at the on position. I jumped 12v to it and it runs great! Now, the ignition switch is good, reading 12v at the purple wire when at the on position. So, it has to be the starter solenoid, right? There is a purple with white stripe wire that runs from the starter solenoid to the coil. Both contacts read 4v with the ignition on and nothing with the ignition off. Replace the solenoid and my problem is solved, or am I over looking something? Thanks for the help.

 

[geriksen]

Re: Merc. chugs but won't run?

O.K., now we are getting somewhere. <br />The solenoid is not your problem though. That purple wire from the solenoid is the bypass wire. That is the wire that was letting it try to start untill you released the key. The problem is going to be either the key switch itself or in the wiring harness to the engine. The way to narrow that down is to move that jumper wire around to isolate the problem. First, try putting the jumper between the red,(or orange) wire on the back of the key switch and the purple wire on the key switch. With that jumper in place start the engine. If it runs replace the key switch and you are done. (btw you will have to pull that jumper off to shut it off)<br />If is does not run you will have to follow the purple wire from the dash all the way to the coil. Somewhere in that line there is a bad connection. Hopefully the key switch does it.

 

[philtheskipper]

Re: Merc. chugs but won't run?

Well, I already tested the ignition switch. It gets power to the purple wire but it's not reaching the engine. Let me ask you this. Would it be safe to run a new wire straight from the ignition back to the coil? Or does that wire supply power to something else too?<br /><br />The coil has two positive wires hooked to it. The one from the starter and a tan or orange wire.

 

[geriksen]

Re: Merc. chugs but won't run?

You could do that and it would work except for one thing. The coil should say on it "for use with external resistor" If it does there is either a resisitor or a resistor wire in that line. The coil shoul only get a full 12v when cranking. That is what the wire from the solenoid is for. While running it should be about 9volts. If you give it 12V all the time the coil gets hot and fails and your points don't last. That resistor wire in on the engine itself. You would need the manual to find it. First, I would look at the wiring harness plugs, see if they are corroded or loose. The big cannon plug on the enigne would be a good place to start. Check voltage on the purple wire on both sides of the plug, or just clean them all. You have it narrowed down to one wire. Process of elimination will find it. Good luck!

 

[philtheskipper]

Re: Merc. chugs but won't run?

Thanks for all the help. It must be a bad connection somewhere because it is getting at least 4v. I'll monkey around with it tomorrow if the weather permits. I also have a manual with wire diagrams and just figured it out. The diagram states that the purple wire is white instead. This was confusing me earlier. Now it all makes sense. It does show the white wire as a resistance wire back at the engine.

 

[Walt T]

Re: Merc. chugs but won't run?

Follow that wire, make sure there isnt a ballast resitor in the circuit. If not, replace the wire with resistor wire.

 

[philtheskipper]

Re: Merc. chugs but won't run?

The only thing is all the wires are bundled together and are in a protective plastic sleeve. I'll see what happens tomorrow. I might have to cut the protective sleeve off to follow the wire.

 

[philtheskipper]

Re: Merc. chugs but won't run?

Well, looks like I'm going to rewire the whole boat! Anyone know what a repair shop might charge to rewire from the gauges all the way back to the engine? If it's going to be too much I'll do it myself. I know the wire harness itself is going to cost an arm and a leg.

 

[geriksen]

Re: Merc. chugs but won't run?

You can do it. For a cheap fix you can just run a new purple wire outside the harness. Buy a ballast resistor and put it between your new wire and the (+) terminal on the coil. Leave everything else just like it is. It might not look that pretty but it should fix your boat.

 

[philtheskipper]

Re: Merc. chugs but won't run?

I found that a few of the wires at the main wire harness plug are frayed and just nasty looking. That's why I said I need to replace the whole wire harness. Plus a couple of my gauges aren't working. I winterized the boat and it's in a warehouse for the winter. I could replace all the wiring over the winter but would rather take it somewhere if it's going to be reasonable.

 

[geriksen]

Re: Merc. chugs but won't run?

ah ha!<br />If I had known you had guages out I would have pointed to the harness sooner. You can buy the harness in lengths suited to your boat. It is not that hard to do. They come with all the guage terminals labeled. Time consuming but not difficult.<br />Make sure you tell them the year of the engine there was a change in the harness back then. Get the wrong one and you will pull all your hair out trying to make it work.

 

[philtheskipper]

Re: Merc. chugs but won't run?

I'll look into it. My trim and gas gauge never worked ever since I bought the boat. My voltage gauge works when it wants to. When you order the wire harness does it come with both the male and female harnesses?