79 Merc 40hp starting problem

I picked up a 40 2 cylinder thought the motor was in good condition but now I'm having second thoughts. <br /><br />This is whats happening, <br /><br />Problem 1 Motor turns over, kinda slow. I found some corroded wires at the front of the motor which should still hold a alright current but I will be replaceing at soon as I know it will start. <br /><br />Problem 2, I had a hard time getting spark, I pulled the plugs out grounded them on the block and ground wire and I got spark once, came back to the motor a few days later nothing was touched and now I can't get spark again?<br /><br />Question? Are the 79-83 40hps all the same? I found some info that said that before but I can't find it need to check if that is correct.<br /><br />If someone could give me some advice that would be great.<br /><br />Thanks

Re: 79 Merc 40hp starting problem

Merc used some really BAD wire in the 1970's, I suspect this may be the cause of your problem. Try disconnecting the kill switch wire first and see if you get good spark then. If it does start, you can kill it with the choke. If that doesn't do it, you may need to work your way through the rest of the wiring. <br /><br />I have a 1976 Merc 200 that wouldn't start, it turned out to be the kill switch wire shorting where it went under a clamp. Replaced that wire and all was well. But on mine, the CDI box had already been replaced, and that meant most of the rest of the internal wiring was new. Good luck and let us know what you find out.<br /><br />Also, clean the contacts and check the cables on your starter motor circuit from the battery to the starter and make sure you have good ground and no voltage drop. Low voltage will cause you to burn up your starter. Check voltage through the system with a meter.

Re: 79 Merc 40hp starting problem

Thanks for the info, I think I'm going to pick up the book and then start checking voltage, good thought about the kill switch, I did see spark once so I'm hoping the CDI box is not gone. Looks like I have my work cut out for me... I'll let you know what happens might be a bit before I get a chance to really put some time into it.<br /><br />Thanks<br />mike