the path of a spark? 1970/ 80hp Merc

[bkyser]

I have an 80hp. Mercury 800 with Thumderbolt igintion, 1970 Ser#2881497... and of course like half the other posts, no spark. It ran fine. I stopped it, it would not start again, it had intermittent spark, sounded like it wanted to run, but wouldn't take. I replaced the external harness with a used one and it ran for a brief time, now have no spark at all.<br /><br />I'm not sure if this is the way it is "supposed to be done", but it makes sense to me.<br /><br />Can someone tell me what path the spark takes... I want to systmatically check each point where a problem could occur. I've replaced the plugs, and wires, I don't know what the points should even look like, so I'll probably change them and the Distributor cap(still cheap) . What should I check next in line? and in what order is the most likely problem?<br /><br />My other (probably stupid ) question is, I bought the boat used, he had a new battery in the boat, and I used it for two years..... now I read on a troubleshooting sight that maintenance free batteries can "over charge" and ruin the CD.... what is the CD, and can it be replaced? <br /><br />Thanks

 

[cclemon]

Re: the path of a spark? 1970/ 80hp Merc

MC,<br /><br />There are no stupid questions. People who ask questions are smart and that includes you. Welcome to the forum.<br /><br />I don't know what post you read that said a maintainence free battery would cause a CD failure. When they say CD, I assume they are talking about the Capacitive Discharge Unit, some people call it a Power Pack, some call it an Ignition Module. It is the unit that detects an input from the rotation of the flywheel and amplifies that signal then sends it to the coil which amplifies it again and sends it to the spark plug. <br /><br />A maintaince free battery, just meens the top is mostly sealed and you should not have to add water to it. It should not be more suseptable to overcharging that a maintainence type battery. <br /><br />Some older charging system, do not have a regulator, and therfore could charge a battery at a higher rate of current. This would shorten the life of the battery, but should not damage the CD unit. <br /><br />You can get a manual for your engine. It will provide you with systematic test for the ignition.<br />Manuals are available from several location. Here is where I got mine. http://www.a1discountprop.com/selocm.htm

 

[bkyser]

Re: the path of a spark? 1970/ 80hp Merc

I got the info about the maintenance free batteries from www.outboardparts.com/troubleshooting/troubleshooting7.htm<br />I also found it at a couple of other sights. I thought the same thing, I would think that it would damage the battery first. They say at the above link, that as the battery gets over charged, you run into intermittant spark... that's why I thought it sounded familiar... maybe the battery did eventually fry something, and that's why there is no spark? I ran the boat all day, the last day it actually ran.... <br /><br />Thanks for the info, I'll start by checking the power pack.... and the battery just so happens to be dead as a doornail right now...Hmmm