merc 470 eating up coils.

[ferrall]

Have an 1981 merc 470 that was running fine and then decided to quit. I checked spark and didn't have any off the coil so I assumed the coil. Removed the wires off the terminals and the coil started leaking fluid so I assumed bad coil. Bought a new coil and installed and it started right up. It ran for a while and quit again. Same issue. No spark at the coil. Could it be a bad coil again? Or is something eating them up? Could my distributor be bad?

 

[Don S]

Re: merc 470 eating up coils.

When you get it started again, and before it destroys another coil, hook up a DVM to the battery, start the engine and rev it up to about 1500 rpm and see what the voltage output is.
If you have the OEM charging system, you may be pumping 16 or 17 volts into the coil when it's running.

 

[fmalott]

Re: merc 470 eating up coils.

When you get it started again, and before it destroys another coil, hook up a DVM to the battery, start the engine and rev it up to about 1500 rpm and see what the voltage output is.
If you have the OEM charging system, you may be pumping 16 or 17 volts into the coil when it's running.

i agree with Don S sounds like you still have the old voltage regulator system which is over charging. when i was new to iboats i bought a 1983 470 with the dreaded voltage regulator i was blowing batteries and coils then i learnt about the alternator conversion has been no problem since

 

[sambluckie]

Re: merc 470 eating up coils.

I don't mean to hijack a thread, but after reading this I am worried I may be headed for the same problem! I have a '85 mercury 3.7 with the OEM charging system. I noticed while running at about 3000 rpm the volt meter was 16-18. Where should it be? I will post a new thread if you suggest.

 

[stonyloam]

Re: merc 470 eating up coils.

About 14, time for an alternator conversion. Check out http://www.breezeworks.net/

 

[fmalott]

Re: merc 470 eating up coils.

About 14, time for an alternator conversion. Check out http://www.breezeworks.net/

X2 on what stonyloam said you will start having problems do it now

 

[generator12]

Re: merc 470 eating up coils.

X3 on stonyloam...

My 1985 470 was putting out 16 volts prior to replacement with the Hunn-Finn high mount. Now it's a nice even 13.5 at all speeds.

The battery won't last long at 15-16. If it goes higher you could lose light bulbs, sound system, etc. as well.

The conversion should be done ASAP.

 

[ferrall]

Re: merc 470 eating up coils.

i agree with Don S sounds like you still have the old voltage regulator system which is over charging. when i was new to iboats i bought a 1983 470 with the dreaded voltage regulator i was blowing batteries and coils then i learnt about the alternator conversion has been no problem since

I actually have already converted over to the alternator option, a few years ago. Regulators are too much $$ to keep them in service. Any other ideas?

 

[Don S]

Re: merc 470 eating up coils.

Did you check the voltage? Alternators can fail too, just not as often.

 

[ferrall]

Re: merc 470 eating up coils.

I didn't get a chance to check it because the boat is left at my cabin. What kind of voltage should I be getting off the battery and how much is too much or little?

 

[stonyloam]

Re: merc 470 eating up coils.

A fully charge battery when the boat is NOT running should be 12.6 volts, when running, about 14. Each cell in a 12V battery should give you 2.1 volts (6 cells), so if you are reading less than 11 you should suspect a bad cell.

 

[ferrall]

Re: merc 470 eating up coils.

I guess I'm kind of confused on what the battery has to do with my coils going bad. I thought this had more to do with the alternator

 

[Don S]

Re: merc 470 eating up coils.

High voltage is what kills coils. Defective alternators cause high voltage. Batteries do not cause high voltage.

What it all boils down to is you need to check the voltage going into the coil with the engine running above 1500 rpm.

 

[ferrall]

Re: merc 470 eating up coils.

Thanks Don. So, anything above 14V @ 1500rpm I should be worried about, correct? If so, then I need a new alternator or get this one rebuilt? Also, should I be checking voltage at the coil terminals or battery? Does it matter how the coil is mounted? I have it mounted horizontally not vertically as it was originally before the alt. conversion.

 

[ferrall]

Re: merc 470 eating up coils.

UPDATE: Well I bought 2 more coils and installed and tried to start it. It would not. Installed the other, same thing. No start. So I was unable to check voltage. I still have the same symptom...no spark. Could it be my distributor or the resistor for the coil?

 

[carguy001]

Re: merc 470 eating up coils.

you could now have a bad set of points and condensor, if you have not replaced the points in the last year your due any way they are $10-$15

 

[ferrall]

Re: merc 470 eating up coils.

I kinda gave in and took it to someone because it's at my cabin and I'm not there much. He couldn't find anything wrong. It started right up for him and had 13.5V off the alternator. Beats me but I think I'll do the points and condenser anyway.

 

[Eric 3.7LX Alpha 1]

Re: merc 470 eating up coils.

You could have had something as simple as a loose wire, but it sounds like it's not fixed yet. You really need to get a digital multi meter if you are going to work on your boat.

You could have tested voltage in seconds with it...as well as resistance on the coil and there would be no guess work if the coil was good still or not.

They are cheap money and handy to have.

 

[fmalott]

Re: merc 470 eating up coils.

I kinda gave in and took it to someone because it's at my cabin and I'm not there much. He couldn't find anything wrong. It started right up for him and had 13.5V off the alternator. Beats me but I think I'll do the points and condenser anyway.

if your going that far convert to electronic ignition more reliable

 

[ferrall]

Re: merc 470 eating up coils.

I do have a multimeter but I couldn't get it started to check voltage. I ran it this last weekend and I got just over 14V at the alternator and less at the coil. I have a theory but I'm not too sold on it.....The whole no start thing happened a couple more times this weekend and all I did was jiggle the throttle and then it started. Could it be the neutral safety switch? This is where I'm not sure about my theory because I always thought that switch wouldn't let the engine crank and my engine did but just didn't start. Any ideas?