1972 50hp wiring problem

[jbjennings]

Well,
My 50 is ready to run, but I am having a problem. The motor starts and runs on both cylinders, cranks, and turns off with the key, and the electric choke works (although the warm up circuit immediately kicks the choke a little closed without the choke switch being used).

The motor shifts perfectly.

Problem: The motor has a power drain with the key in the off position. I've not checked the amperage draw yet but it isn't that bad. I'm suspecting the key switch just doesn't turn all the circuits off properly and the cold choke switch is drawing current all the time, even with the switch off.

Question: As far as I can tell looking at a wiring diagram for a '72 65hp evinrude, it's wired correctly. Could the problem be in the switch itself, or is there probably a short somewhere that I can't seem to find?
I'm not proficient with wiring problems, although I can usually muddle my way through it.
Finding shorts are really tough for me!

Thanks,
JBJennings

 

[jay_merrill]

Re: 1972 50hp wiring problem

Do you have a 50hp or a 65hp motor? If its a '72 with three cylinders, its a 65hp. If it has two cylinders, it would be the 50hp.

If the thermal choke is actuating, you should be able to see the plunger move if you disconnect the circuit at the bus block. Try alternately disconnecting and connecting the circuit.



???

 

[jbjennings]

Re: 1972 50hp wiring problem

sorry,
I meant running on 2 cylinders, Jay. It's a 50hp. I'll hopefully be able to provide more info tomorrow.
Thanks for the help,
JBJ

 

[F_R]

Re: 1972 50hp wiring problem

Check (test) the rectifier and the "monkey nutz" diodes. Check for crud in the yellow plug.

Or, rig up a small dash light bulb and connect it in series with the switch purple wires, one at a time. If it lights. there is a drain. Or, connect it in series with the fuse holder--that will check them all at the same time. If it lights there, then proceed with the individual wires.

 

[samo_ott]

Re: 1972 50hp wiring problem

If you have a simple Volt-Ohm meter there's usually a current measurement position on it so you can see the actual current drain through certain tested circuits. Always test current in series. And don't test over the rated amount on the meter or you will fry it instantly.

 

[jbjennings]

Re: 1972 50hp wiring problem

Now I'm scared!
The short is eliminated if I take the purple/green striped wire off the terminal. The wire I'm taking off to break the short is attached to the terminal from the left side.
I'm worried this wire is one that has something to do with the electric shift.
I'm going to fiddle with it a little more while I still have daylight and see if the problem can be found.
Thanks for the help guys,
JBJ

 

[F_R]

Re: 1972 50hp wiring problem

That is the alternator feed to the electric shift. As I said, check the rectifier and monkey nutz.

 

[jbjennings]

Re: 1972 50hp wiring problem

F-R, I believe I've found those monkey nutz you speak of behind the terminal blocks. Is this the "diode/lead" in the parts diagram? If so, how the heck do I test it? Just like the rectifier?

I tested the rectifier and I believe it to be o.k.
Using Joe Reeves Ohm method the current only seemed to flow one way through both yellow wires. However, with the rectifier test mode on the meter I have, it seemes I get no resistance either way when jumping the red and yellow/gray stripe wire, but current in only one direction jumping the red to yellow wire.

Would you mind telling me how to test the monkey nutz? Is it likely that the diode is bad and letting current flow backward, causing the short?
I'm not fully understanding what's going on here.
Thanks, you appear to be right on as usual. I don't know how you do it. You must've worked on a heckuva lot of models through the years!
Later,
JBJ

BTW, the plug has no crud whatsoever.
Also, I'm guessing that the wiring is rigged where the battery and alternator can feed the solenoids in the electric shift, so that the battery is feeding through the monkey nuts or rectifier if the diodes in either are blown? ---just trying to get my head around the problem. Is this correct?

 

[jbjennings]

Re: 1972 50hp wiring problem

I believe I have found my problem. The monkey nutz diodes I tested in a similar manner as the rectifier. I got infinite resistance one way on both wires, but did have current flow the other direction evidenced by measurable resistance. Thank goodness----they're about 100 bucks!

I retested my rectifier, and found that there was no resistance between the red and the yellow/gray striped wire. One-way resistance resistance was found between the red and yellow wire, which I believe to be correct.
SO, bad rectifier, short to ground?????

Will a new rectifier solve the problem, or do I need to search for the reason for the bad rectifier as well? The bad rectifier didn't look like it had ever been hot in any way. The motor had been underwater, however, in a flood. Perhaps the seal on the rectifier wires could have leaked and water got in, somehow ruining the rectifier? Or, do rectifiers go out for no reason sometimes?
A new rectifier is $50 without shipping. I hope this solves the problem.

I really appreciate the help. I certainly couldn't have found this problem without it.
WIll report back with results when new rectifier comes in. Hopefully some full power pics, as well!
JBJ