1992 Yamaha 9.9hp 4 stroke - Starts and then won't start

[DeanHensler]

My neighbor has the engine above with a Yamaha 703 remote control unit on it. Its been running fine for years and all of a sudden it won't start. I've done a lot of work on my evinrude so he asked me if I could help fix it. This is the strangest thing. I went down to look at it and tried to start it. It fired right up. Then I turned it off and tried to start it again. Now it won't even turn over. I went home to get my tools and when I got back a couple hours later I experienced the same thing! It started right up, then after shutting it off it wouldn't start again. So then I went to tracing wires to make sure everything was wired correctly. Now is where it gets SUPER strange, coming out of the 703 remote control unit there are about 5 wires (2 black, 1 yellow, 1 Green and 1 Pink). I unplugged all of them and tried to start it. It fired right up again! Then after shutting it off, it won't start again. I've traced a ton of wiring and I've found that it blows the fuse in the engine compartment whenever you turn the key to the on position (not actually starting it).

Anyone know what might be causing this? It really seems to run fine after you let it sit a few hours. But won't even turn over when it's warm. Attached are some pictures showing the serial number, the fuze that blows and the control unit.

 

[DeanHensler]

No Title

Here are the pictures

 

[Mohawkmtrs]

Try tracing the blacks and brown inside the control box looking for a short.

Brown turns into red and goes to the fuse.

 

[DeanHensler]

Try tracing the blacks and brown inside the control box looking for a short.

Brown turns into red and goes to the fuse.

Thanks I will try that. Any idea why it would start cold but wouldn't start warm?

 

[DeanHensler]

No Title

Okay I took the 703 control box apart today and here's what I found. Lots of wires and some of them have damage, however, non are broken and I made sure none were touching each other. The red wire in the control box gets no power with the key on if the fuze in the engine is blown. If I put a new fuze in the engine the red wire in the control box gets power, but blows the fuze immediately if I turn the key on. I put a very heavy fuze in there and the motor started and ran fine, but the black wires in the control box immediately got very hot and started smoking. So it appears that a power wire is touching a ground wire somewhere... Any ideas how to troubleshoot this? All the wires outside the box and through the harness look fine to me.

 

[Mohawkmtrs]

If the black wires got hot and started smoking, that's your clue that there is high resistance (making heat) that is blowing your fuse.

It also looks the blacks are damaged in the picture.