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1990 Euro F3 Coil Voltage


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I have a 5.7 mercuiser in my boat and was wondering what the voltage should be at the positive terminal of the coil. The voltage is measuring 5 volts right now and to me that seems low.. I would assume it should be 12 volts since its a 12 volt system. The engines been running like crap, I replaced the coil and put an electronic ignition module in to replace the points. Could the this be the issue?

thanks Eric

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I have a 5.7 mercuiser in my boat and was wondering what the voltage should be at the positive terminal of the coil. The voltage is measuring 5 volts right now and to me that seems low.. I would assume it should be 12 volts since its a 12 volt system. The engines been running like crap, I replaced the coil and put an electronic ignition module in to replace the points. Could the this be the issue?

thanks Eric

I've seen the exact same thing on an Echelon (around '93 or 94?) and the problem was a loose connection in the wiring harness. Put a new wire from the coil to the the other side of the wiring harness plug and now it always measures 12V. Has run great for years now after that fix.

Follow the wire to different places in the harness until you find where it drops from 12 to 5, then replace or repair the bad connection.

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I've seen the exact same thing on an Echelon (around '93 or 94?) and the problem was a loose connection in the wiring harness. Put a new wire from the coil to the the other side of the wiring harness plug and now it always measures 12V. Has run great for years now after that fix.

Follow the wire to different places in the harness until you find where it drops from 12 to 5, then replace or repair the bad connection.

After doing some research, that seems to be the consensus.. I'm gonna check into it.

Thanks

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Looking at that wiring diagram, the problem that I fixed was in the purple wire right at the Y where it splits off to the alternator.

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Come to find out its 5 volts when the key is in the on position and the engine is off. Once the engine is running the wire goes to 12 volts. Still having a problem with the engine not running well. It died today on the water after being off the trailer for about 3 minutes, and would not start back up.. I took out the ignitor and put the points back in and got it to fire back up in my driveway. So maybe tomorrow I'll see how this works

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Please post what you find. I too had problems after I put in the pertronix. Fired right up. Took to the lake... ran crappy (wouldn't idle and often died). Thought it was the carb. Too it wide open across the lake, and it would putter out at high rpms. I was on the lake, without a volt meter so I replaced the pertronix on the lake with my points... runs fine again. I figured I had a resistive wire and I'd fix it later... now that the diagram appears to show otherwise, I'll have to dig for the answer.

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martinarcher

I ended up buying the Pertronix coil after having rough running issues with my boat, but the boat came to me with the Pertronix and an Accel Hot Shot coil. Not sure if you need to update to a bit hotter coil with the Pertronix kit. I know my rough running issues ended up being my fuel pump as the Pertronix set-up worked fine for almost a year after I bought it (until my fuel pump problems) and continues to run like a top. I thought I'd share my coil info as well in case it helps. I know the chrome Hot Shot coils are available at the parts store for a pretty reasonable price.

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martinarcher

Come to find out its 5 volts when the key is in the on position and the engine is off. Once the engine is running the wire goes to 12 volts. Still having a problem with the engine not running well. It died today on the water after being off the trailer for about 3 minutes, and would not start back up.. I took out the ignitor and put the points back in and got it to fire back up in my driveway. So maybe tomorrow I'll see how this works

That's weird you only have 5 volts before cranking or starting. I don't understand that. Do the wire colors on your coil agree with the wiring diagram or are the different?

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That's weird you only have 5 volts before cranking or starting. I don't understand that. Do the wire colors on your coil agree with the wiring diagram or are the different?

Everything matches stock diagrams, maybe its just a faulty ignitor. There are only two wires on the ignitor so instalation is self explanitory. I just bought a new stock replacement coil so maybe that wasn't agreeing with the ignitor? I just about replaced everything else( fuel filter, fuel pump, lines, cap, rotor, plug wires. Maybe bad gas from over the winter?? There is an aftermarket eldelbrock marine carb on it. It seems as though all signs are pointing to that. So I think I'm going to ditch that junk and get a stock carb for it, and get it back to the way its suppose to be.

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Come to find out its 5 volts when the key is in the on position and the engine is off. Once the engine is running the wire goes to 12 volts. Still having a problem with the engine not running well. It died today on the water after being off the trailer for about 3 minutes, and would not start back up.. I took out the ignitor and put the points back in and got it to fire back up in my driveway. So maybe tomorrow I'll see how this works

That's funny my purple wire on the coil is 12v whenever the ignition is on, even if the motor is not running. But I don't have points. I don't think my boat ever did have points but can't remember... now in my 16th summer with it.

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martinarcher

Everything matches stock diagrams, maybe its just a faulty ignitor. There are only two wires on the ignitor so instalation is self explanitory. I just bought a new stock replacement coil so maybe that wasn't agreeing with the ignitor? I just about replaced everything else( fuel filter, fuel pump, lines, cap, rotor, plug wires. Maybe bad gas from over the winter?? There is an aftermarket eldelbrock marine carb on it. It seems as though all signs are pointing to that. So I think I'm going to ditch that junk and get a stock carb for it, and get it back to the way its suppose to be.

Before you trash your carb I'd check a few more things. The biggest would be the timing. I doubt installing an Ignitor module would affect your timing, but it is in the cap and it is certainly possible. Do you have a timing light you could use to check the timing at idle and also verify you have advance when RPM's increase?

My Merc manuals are on my other laptop, but I think our Mercs should idle at 13 degrees BTC if I remember correctly.

I still think your purple wire has a bad connection somewhere and os the reason for the 5V instead of 12 before the start. I'd check the crimp at the ignition switch. I would also pull apart the engine wiring harness plug and look for corrosion, clean up the connector, and add dielectric grease.

Edited by martinarcher
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Before you trash your carb I'd check a few more things. The biggest would be the timing. I doubt installing an Ignitor module would affect your timing, but it is in the cap and it is certainly possible. Do you have a timing light you could use to check the timing at idle and also verify you have advance when RPM's increase?

My Merc manuals are on my other laptop, but I think our Mercs should idle at 13 degrees BTC if I remember correctly.

I still think your purple wire has a bad connection somewhere and os the reason for the 5V instead of 12 before the start. I'd check the crimp at the ignition switch. I would also pull apart the engine wiring harness plug and look for corrosion, clean up the connector, and add dielectric grease.

Went over all the conections in the harness, everything was fine. Checked the timing on saturday, and that seemed fine. I think it was at 8 degrees btc idleing, but it did advance fine when i brought it up to 3500. I thought 8 degrees was right, Should it be at 13 degrees? Took the boat out last night, and it was running great.. Best since I've gotten it. So I guess it was the ignitor screwing things up?? Maybe I should get a new one with their recomended coil??

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martinarcher

Went over all the conections in the harness, everything was fine. Checked the timing on saturday, and that seemed fine. I think it was at 8 degrees btc idleing, but it did advance fine when i brought it up to 3500. I thought 8 degrees was right, Should it be at 13 degrees? Took the boat out last night, and it was running great.. Best since I've gotten it. So I guess it was the ignitor screwing things up?? Maybe I should get a new one with their recomended coil??

It might be 8, don't do anything with my 13 off the top of my head. Crazy.gif I could be way off. A GM smallblock won't throw a hissy fit over 5 degrees anyway.

It does sound like the Ignitor could certainly be the problem (or at least something related). I would give Pertronix a call and see if they have any ideas that we haven't tried. I'm sure one of their Hotshot coils will be a suggestion as they sold me one when i was having issues, but I do like the coil. Thumbup.gif It is a high quality epoxy coil. I think it was worth the money. I bought mine off them, but I think the local NAPA stores carry them as well if you want to get one quick.

Keep us posted!

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Mercruiser recommends 8 degrees BTDC at idle for ignition timing. The other timing criteria is 32-33 degrees BTC at full advance. You might find that if you want the 33 degrees, you will need a bit more timing at idle.

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I still think your purple wire has a bad connection somewhere and os the reason for the 5V instead of 12 before the start. I'd check the crimp at the ignition switch. I would also pull apart the engine wiring harness plug and look for corrosion, clean up the connector, and add dielectric grease.

:plus1:

Your ignitor may have been the problem but I still think you might have an intermittent problem with your wiring. Does it still read 5v at the coil? If so, I'd check the v just before the wiring harness plug and maybe a couple other places.

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