johnson 115hp coil issues

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newtong_ware

Seaman
Joined
Sep 18, 2005
Messages
59
I've been working on my 115hp '76 etl trying to get it running more reliably. I have rebuilt the carbs and things were looking better. Now the port cylinders do not fire. <br /><br />I did replace the kill and start switches, and according to old posts I checked for volts at the blk/yel wire at power pack. about 2mV DC. Pretty darn low. With kill switch lanyard in place the circuit to the power pack is open when ign key is on and closed when key is off. With lanyard pulled, blk/yel grounds out period. I had previously checked the ops of the start switch(good) and verified the kill switch ops (good). So I do not think this is a problem....?<br /><br />I did the sensor coil high and low ohm tests and all was within specs.<br /><br />I checked the coil impedance through the coil and to ground on the port coils vs the starboard coils (primary)and all were the same. The lower cyl coil on the port side was different from the other 3 and it looked like it had been getting warm where the hi tension lead enters the coil.<br /><br />I cannot do any of the other tests unless I can come up with the neon tester referenced in the manual.<br /><br />So I guess my questions are these:<br />Any suggestions on other things / tests to consider?<br />Where can I get the neon tester and how much about?<br />Whats the best source for coils and powerpacks if I decide to just get them all. <br /><br />I have had the boat two years now and it is either going to act like it should this year or I might do something rash with either a chainsaw or gasoline or maybe even both. :confused:
 
L

ledgefinder

Ensign
Joined
May 2, 2002
Messages
916
Re: johnson 115hp coil issues

Could be just the pack. Try swapping the sensor coil leads to be sure. Don't try to start the motor that way, just see if the problem moves with the sensor coil lead. <br /><br />When push comes to shove, you need to be able to read the signals coming from the sensor coils, charge coil, and from the powerpack, in order to make sense of things. Two instruments that will do, aside from the 'neon tester', are a peak reading voltmeter, or an oscilloscope. A regular voltmeter won't do. Before I got my scope, I just had a known good pack & sensor base to swap in & out, for diagnosis. You might consider same - try eBay for the parts. Not very expensive off season. 1973-77 V4s will swap, except NOT the 1977 140hp. <br /><br />It is possible for a sensor coil to have normal resistance, but not be putting out enough output to trigger the pack. Sometimes when that's the case, that sensor will kick in at higher rpmsm but not at idle. Rapair sells a plastic ring that sits on the crank taper, and has the same diameter as the inside of the flywheel, to allow you to set the sensor-flywheel gap. Also can happen due to leakage from the coils to the timer base frame. <br /><br />I don't think it's your charge coil, because I think all four cylinders use the same charge coil on that motor (right? - all my books are in a storage shed). I have yet to see a bad charge coil on a 1973-77 PP4 ignition, though I understand they melt on newer motors.<br /><br />A bum spark coil can harm your powerpack, at least in theory.<br /><br />Joe Reeves talks about a control box voltage leakage problem that can mess up the ignition on 'red plug' motors, but it generally blows the pack.<br /><br />If you can scare up a scope, or a peak reading voltmeter, you can diagnose the problem directly. Otherwise, I'd find some good used parts and swap for diagnosis.
 
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newtong_ware

Seaman
Joined
Sep 18, 2005
Messages
59
Re: johnson 115hp coil issues

Good info, thanks a bunch. My digital voltmeter does have a peak hold function. Any idea what voltage and time period we're talking about? I am not sure what the response curve is on this thing. The only other option is I might find a o-scope to borrow. Same question as to voltage applies here too I guess.<br /><br />I have always hated swapping parts to troubleshoot but sometimes it can't be helped. I worked on copiers, faxes, printers and such for 13 years and I had it work for me and against me more than once.<br /><br />Thanks Again,<br />Newt
 
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ledgefinder

Ensign
Joined
May 2, 2002
Messages
916
Re: johnson 115hp coil issues

My manuals are in a storage garage. You're looking for the numbers for a 1973-77 V4 "PP4" style ignition. The peak reading will suffice - that's all they publish for figures anyway.
 
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newtong_ware

Seaman
Joined
Sep 18, 2005
Messages
59
Re: johnson 115hp coil issues

Guys, I wanted to finish up this issue. I replaced the two port coils and the boat did much better. But since I had also ordered a power pack, I went ahead and replaced that too. The boat runs great now! Is it just my impression, or is there a reason that the power pack seemed to finish off the problem. I thought th epower packs were pretty much a go/no go kind of thing. Anyway, thanks again for everyones help. >>>>Newt
 
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