1974 OMC 190 Stern Drive Electric Shift - No Reverse

I have been reading a bunch of simalar posts, all very helpful but I still need some help....

Boat was running fine, i use it weekly. I was running about 3/4 throttle on glass smooth water and suddenly the speed slowed and i felt a lot of vibration. I stopped and put it in nuetral, vibration stopped... I put it in fwd and gave it a little gas, more vibration. I tried reverse, same thing. I shut off the motor and raised the lower unit and one of the prop blades had fallen off. i didnt hit anything, it just fell off. very old prop, probly the original. anyway, i had a spare so limped in at very very low speed and swapped props.

went back out and all seemed fine, except i started noticing a failure to go in reverse some times. I mean I could shift the electric witch to reverse and it wouldnt engage. then eventually it stopped ever working in reverse, just forward.

I checked the the switch, its good. I disconnected the forward and reverse wires at the rear of engine and get about 3 and something ohms on each. I plugged the fwd wire onto the reverse wire and hit the switch and the wire burnt in half almost instantly.

Seems i have a short somewhere in the wire or the reverse coil. How hard is it to take apart to find out and any tips?

thanks for any pointers

12V and 3 ohms = 4 amps

no 18 ga. wire is going to "melt in half" because 4 amps flowed through it

maybe it read .3 ohms, which would draw 40 amps

that would make it get quite toasty

4 to 7 ohms is normal, which means when it's working right, it will draw 2 or 3 amperes contiuously

im really not versed in using a meter, i set it to the ohm thing and put the black to the ground battery terminal and touched the red to the fwd wire and then the reverse. I had to turn the little dial on the meter to get the dial to register a low number, if i turn the dial up it reads higher... going to google meter reading now

i forgot to mention that on the dash amp gauge in fwd it only drops a hair, like maybe 2 at most but when i clicked it in reverse (prior to melting the wire) the gauge would drop way down as if it were pulling a lot of current

There seams to be a short in the shift the wire.Test between the housing and the banana plug.It should have blown a fuse be for it melted a wire.That would be the next thing to check. If the needle or reading goes all the way over you have a shorted wire.Most likely were it goes through the upper housing.
Good luck

i tossed my coroded antique analog meter and bought a digital one, after reading the instructions i tested the ohms and found 0 in the reverse and 6.2 in the fwd. I traced the wires through the upper unit area and down below the spring clip are and cut them there as the couple feet of wire through the upper was in pretty bad shape... i retested just outside the lower unit and find the same measurements. unfortunately it looks like i have to go inside to find the problem. going to read the manual on removal now, if anyone has any tips i would appreciate it.

I pulled the prop and got to the reverse wire. the little plate that the 4 bolts go into that is behind the prop appears to have spun a hair cutting into the wire (as shown in the pic)

then in the second pic you can see where i pulled the wire out just a bit and tested the ohms on the reverse coil, its 6.2 and still good but now i have 2 questions:

1. can that wire be spilced with anything? like maybe waterproof heat shrink splicer? i have my doubts on that one....

2. why did it slip and cut the wire in the first place?

thanks to all in advance

Why it slipped got me. Solder and heat shrink wrap and you should be good to go.

I used a sleeve crimp type connector and heat shrink to put it back together. Took it out for a test yesterday and worked great. I did have quite a bit of water come in through the engine hole where the shift wires go through. I used some silicone to seal the hole since i had to replace the fried wires and it didnt hold.

what is good to fill that hole?

thanks

marine tex, maybe jb weld.

I used 4200 on my speedo hole

thanks. i used jb weld, i can always drill it a bit if i ever need to get the wire out again. will take it for a test saturday.

No leaks all is well, thanks much