Just Fried a New Coil with my Mercotronic

[crosbyman]

coils can only burn for one reason…to much juice

the wire size naturally limits the current by it’s resistance characteristics (diameter x length) but if the operating voltage is to high more amps will flow (cram in ) increasing the watts it needs to dissipate within the coil.

With nowhere to go the heat rises and fries the coil’s wire insulation (varnish) further reducing (shorting out) the overall resistance causing more heat etc… etc…

In other words…. (to much voltage & amps "watts" X to much time)

So either the Merc O tronic is defective , not adjusted or used properly (?)
or… that coil had a bug in it and it is just as well it died in the shop.

jm (saturday morning) ho…

Joining AOMCI has priviledges 🙂

[RICHARD A. WHITE]

I can’t imagine it frying the coil….You can, and I have seen it, not done it, run a Ford Model T buzz coil on 12 volts…clearly they were made for 6 volts…I am not saying to do that but have seen it done….The short period of time needed to spin up the dial to increase voltage should not have done it…unless you let it stay there for a long period, and even then would that have caused it to go bu-bye???
Not anywhere close to an electrician, but if you only have 7.5 volts input and that coil fried, …it was bad to begin with….Just my shade tree opinion….

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[kevinrude]

Yeah, I think what I am going to do is take one of my many cracked OMC coils that test out as working on the multimeter and run it through the MercOTronic. If it fries, no big deal and I will know that the MercTronic has a problem. If it doesn’t fry, then I will know it was the coil. Of course, either case doesn’t disprove operator error 🙂 , but I did follow the instructions. We’ll see what happens.

[ken-hall]

I also use a Merctronic tester in my shop.Recently I began getting "questionable" results.Pulled out the manual.Seens as though when the 7.5 volt battery gets below 6.5 volts,it doesn’t work correctly.The battery was new in 2011.Not sure how long it sat on the shelf prior to my purchase.Anyway,I installed a new battery and it’s back to normal.How long did you perform the power test for?

[RICHARD A. WHITE]

I use a rechargeable 7.2 volt battery, and have noticed strange readings on the meter, place battery on charge for an hour and readings resume normalicy..

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[crosbyman]

if 7.5 volts is a critical point you may want to consider a 9 or 12 volts supply connected to one or more of these "regulators" wired in parallel to give you a piss flat 7.5 volts

(going 2 in parallel will double the amps capacity) just join the identical legs …. two to 12volts two to common ground and the last two will provide flat 7.5 volts.

http://www.futureelectronics.com/en/tec … .aspx?IM=0

I have used a similar model to stabilize my humminbird sounder which was freaking out and shutting down with my Merc 45 high voltages charging my battery with over16v at WOT

connect your "new external 7.5v supply " to the internal battery terminal and you are good to go .

just disconnect the 12volts supply when done. mount the chips on a small aluminum plate to dissipate the heat while in use.

Never had a shutdown on my humminbird after I added the regulator under my console.

Joining AOMCI has priviledges 🙂

[mercuryman]

From Merc O Tronic Model 98 book "For bench use use this analyzer can be connected to an 8 volt storage battery power supply. For 8 volts tap off 4 cells from a 12 volt storage battery. "

[oltimer]

quote Richard A. White:

I use a rechargeable 7.2 volt battery, and have noticed strange readings on the meter, place battery on charge for an hour and readings resume normalicy..

I forgot to mention the same about recharging the battery. I will admit that every couple of months or so, I put the battery on my Genius C3500 for a couple of min’s. It is a must do if your not connected up in muti power.

[dave-bernard]

the using a bigger than 7.5 volt battery wont damage the coil so much as it will destroy the merc-o-tronic.

[foot_doctor]

I am assuming that the Fried coil was a replacement for a Phelon mag. If so, I would be suspicious of the crimped on eylet at the end of the ground leads. I have repaired several that exhibited the same failed condition. Simply stated, the solid copper lead was not cleaned enough to expose the conductive surface to the crimp. Cut the solid copper lead off where it enters the eylet. Scrape off the insulating varnish to expose a clean copper surface, and solder it along the side of the crimp area. A note of caution here: Do not bend the ground leads repeatedly. The solid copper portion is subject to work hardening and breaks easily. R.T.

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