Merc. 470 Coil Burns Out 3 times

[2Dive4fun]

I went diving in my new boat this weekend and lost power. I replaced the coil prior to leaving on the trip due to no spark. After two hours of run time the new coil fails. I replace the coil and continue my dive weekend. At the end of the trip the motor quits again when flushing the motor. No spark. Third coil is out. At this rate I will be in the poor house with a box of dead coils at my side.

I have never had a coil problem in any of my boats until now. Anyone have a reason? The wiring is origional with no extra wires to the coil.

Scott

 

[kevinrich1]

Scott ..... I have owned Merc 470's for years and never had the coil problem that you discussed. However, I can refer you to a "470" expert. I recently bought the electronis ignition upgrade package for both my 470's from Doug Nelson at AAA Marine in Tacoma, Washington. The package is NOT cheap but the coil output is 4 times that of a "normal coil" and they are custom made. I'm certain that Doug can assist you in troubleshooting coil issue. I also have elected to which from a 2 barrel carb set-up to a 4 barrel. This will give me another 20 to 30 h.p. per engine. 470's are great engines ... but there are several ways to make them even better. 1. electronic ingition as previous mentioned. 2. 4" heat exchangers. 3. charging system conversion upgrade.
You also "should" drain the silt out of the waterpump housing to prevent premature wear on the cam seal. Takes only about 15 minutes and will save you a lot of grief. Doug may be reached at 253-565-3578 .... Hope this helps. Kev....

 

[Hank49]

Must be one of the coil wires is shorted. Check the 12 volt primary input. Or the output.

 

[2Dive4fun]

Thanks for the responce. I have ordered new 40,000 volt marine coils that are the same brand as my Electronic Ignition. I also was considering 4 barrell carb system. I purchased the intake manifold on E-Bay and was watching for a good deal on a 4 barrel carb.

Scott

 

[Chuck Tribolet]

Be sure to check the resistor circuit, if there is one (might not be
with electronic ignition). The resistor limits the flow of current
through the coil.

 

[2Dive4fun]

Good news,

I found a bare wire that was shorting out on the manifold. Guess where it goes....

Yes it is the 12 volt wire off the starter cilinoid that goes to the coil. I installed a new wire and bypassed the resistor to a new high performance coil. I think this will fix the problem.

 

[Hank49]

Good news,

I found a bare wire that was shorting out on the manifold. Guess where it goes....

Yes it is the 12 volt wire off the starter cilinoid that goes to the coil. I installed a new wire and bypassed the resistor to a new high performance coil. I think this will fix the problem.

Did you reroute the wire so it doesn't melt again on the manifold?

 

[2Dive4fun]

Did you reroute the wire so it doesn't melt again on the manifold?

No, I have a water pump to keep the manifold cool. As long as my belge pump works I should be fine.

But your idea sounds better.

OK, just jokeing. Yes I did reroute the wire and bypassed the resistor. I need to work at getting the rest of the wire harness more protected from the heat of the manifold. I was looking for the high heat wire cover to protect the wires.

 

[Chuck Tribolet]

Why did you bypass the resistor? It's there to limit the current flow through the primary
side of the coil and keep the coil from burning up.

I also don't see how shorting the power side of the coil primary to ground is going to fry the
coil,

 

[2Dive4fun]

I installed a Pertronix high performance coil which works with a full 12 volt input. It will produce 40,000 volts for greater performance with the Pertronix Ignitor, Electronic Ignition. All I know is there was a bare spot on the power feed to the coil that was up against the manifold. Since this was the only short in the system that I could find, I rewired it to the coil direct and bypassed the resistor as stated in the installation manual.