where to begin?

[BBKING]

I just got an early 70s 50hp johnson, that has been sitting for about 4 years. I have 110 pounds compression in each cylinder but no spark. the wires are pretty dry rotted, so i figured I better start by ordering a new wiring harness and then replacing coil, magneto until i get some spark. Does this sound like a good or bad idea? where should i start?

 

[Xcusme]

Re: where to begin?

Woooah Lucille!!<br /><br />Start off by pulling the flywheel and having a peek at the coils. The older coils will have outer casings that have cracks. These cracks allow moisture in and they arc the high voltage to ground, thus, no spark. A good inspection of the points and condensers is next. Replacement coils, points and condensers are cheap and easily replaced. Randomly replacing parts can get a little pricy so find out what is defective and then replace. Check back here is you run into problems. A factory manual is a really nice thing to have handy too and money well spent.

 

[bubbakat]

Re: where to begin?

Every outboard motor requires 3 basic things to run properly: an uninterrupted supply of fuel and air in the correct porportions, proper ignition,at the right time and adeequate compression, If any of these are lacking the motor will not run.<br /> the electrical is the weakest link<br /> SO with that in mind and you have no spark I would say you have yourself a good plan.<br />keep us posted will be more then glad to help.

 

[The Marine Doctor]

Re: where to begin?

Erm..If its the 70's vintage 50hp...you will have a powerpack..stator..sensor coils and ign coils.<br /><br />I would not start changing parts at random.<br /><br />Money goes with the powerpack as the problem.<br /><br />TMD

 

[OBJ]

Re: where to begin?

Respectfully disagreeing (sorta) with my estemed mates.....give the wire harness a good look over. If the harness is as dry rotted as you say and the insulation will crumble easily, check connections at multiple plugs and be sure you have no wires "crossing" at these juctures (neat word). Chances are the damage is already done and you have problems in the ignition system from a possible short in the wiring. Don't ferget to check under the flywheel also as Xcuseme suggested.

 

[The Marine Doctor]

Re: where to begin?

Now that is why I spend most of my time in the Mercury Force/Chrysler posts <br /><br />TMD

 

[OBJ]

Re: where to begin?

Hey Doc....see that little head banging at the bottom of my posts? That's me at the shop

 

[Xcusme]

Re: where to begin?

WOW! What a senior moment! Can't believe I read that as a 20HP...gees

 

[OBJ]

Re: where to begin?

LMAO S'OK X....I donit a time or two also.......

 

[The Marine Doctor]

Re: where to begin?

As long as its caught <br /><br />We have to look out for one another.<br /><br />TMD

 

[BBKING]

Re: where to begin?

i appreciate the help guys, new wiring harness is on the way and i will check out the coils under the flywheel and the timing too. thanks again