Mariner 40ELO 6E9-451908 blows fuse after starting

[neokane]

I recently purchased my grandfathers boat back... it has a Mariner 40ELO 2 cyl, stroke with oil injection. The tag says 6E9 L 451908.
The 20 amp fuse continues to blow sometime after startup.
If I replace the fuse, the unit will start. It runs seemingly fine.
Shut it off, no start. fuse blown.
Side note. on high throttle the buzzer buzzes. but the volume seems linear to the amount of throttle.
Have the manual for a yamaha CV40E. check the rectifier, no continuity.
Checked the CDI unit.. doesn't match values on yamaha manual, but it appears to be a different unit.
Part says 6E9-70 F8T13771 9410
Any ideas where to go next? Any info on test specs for this CDI?
Yamaha part number can come back to a 689-85540-22 but the part looks different. Can it hurt to try as the mariner part 822884 isn't available.

 

[Chris1956]

Look for a short on one of the ign accessories, connected to the ign keyswitch.

When you turn the key to start, the ign accessories wire has no voltage on it. When you release the ign key to the run position, power is put on the ign accessory wire. If it has a short, it will blow the fuse at that moment.

 

[boscoe99]

Why do you suspect the CDI box as being part of the problem?

What is the LIT number of your Yamaha manual? Is it LIT-18616-00-45?

 

[neokane]

I can't seem to find the correct wire harness for this motor. I found one similar, but not correct. it is suppose to be the seloc 1400. but trying to find a digital copy.

Wire harness to commander 2000 seems to test fine. no continuity across multiple terminals. got a new key switch. previous owner reported it sometimes wouldn't turn off with key. may be a hint.
checked the rectifier and it seems to test fine. but now have a rats nest with the wires to get back together. I hate when i didnt take pictures before hand.

 

[neokane]

I didn't I suspected the rectifier.. not sure why.. but thats the mess I have gotten my self in. I believe the CDI is working as it should given the motor runs.
I guess I am just throwing everything out there and see what sticks..

 

[neokane]

Got everything back together, new key switch.. started several times.. then blew the fuse. I am at a loss.

 

[boscoe99]

Look at the main wire harness up near the connector at the front of the motor. Is there a label with the part number on it?

 

[boscoe99]

So you do or do not have a Yamaha manual for the motor? Manual by Yamaha. Not some aftermarket stuff.

 

[neokane]

I do have the yamaha CV40E service manual.. there are some differences though.

 

[Chris1956]

Gee, disconnect the stator wires from the rectifier and then disconnect the red wire from the rectifier. If the fuse still blows, that is not the issue (obviously). Now check the accessory wire (usually purple), and trace it to each gauge and anything else it connects to, looking for melted wires and rubbed off insulation.

 

[boscoe99]

There are numerous connection points within the circuit from the lighting coil to the rectifier and on to the battery. Or from the battery through the fuse and on the start switch. Presumption being that your motor is wired similar to its Yamaha equivalent. Start by disconnecting wires as mentioned above, hoping to find where the problem lies.

 

[neokane]

Isolated the rectifier. Ran jumper to console controls. Started and stop many times. Throttled up and down. Put I gear. No issues.
So new rectifier will be here friday.

 

[neokane]

Dectifier is putting out between 8.5 and 11v from red to ground at 5.5 to 6 amps.
Don't have new rectifier yet. But 20 amp fuse is till holding after removing rectifier from the equations