ignition problem??

[iggyw1]

I have a 70 HP Nissan, 1991 model NS70A2E. I had two batteries on board with a two battery switch so I could run #1, #2 or both batteries. I changed batteries today, afterwards, I could not get any electric to the motor!! I have lights, radio, pumps, horn, etc. No electric coming from key to starter, no electric choke when I push key in, and no moving motor up or down with key switch. I figured maybe I crossed a wire or two, so now I disconnected the battery switch went directly to one battery only with the motor.

I hooked up the motor wires (pos. & neg.) directly to one battery, and I still get nothing! I do not know if there is a breaker or a fuse somewhere on the motor that may have blown?? There is an orange wire that looks like it comes from up front under the floor with an in line fuse. I checked this fuse and it is good.

The kill switch is being held out o.k. with the correct horseshoe looking thing on a tether. Motor tilt still not working. no choke when pushing in the key nor no start nor turn over when I turn the key to start position. How can I test the kill switch and or the ignition switch itself? Is there a fuse or breaker that I should be checking somewhere else other than the orange wire? Does the orange wire have anything to do with the ignition switch?

Thanks!

 

[pvanv]

You likely connected power backwards for a brief bit and blew the fuse.

 

[iggyw1]

You are correct. I do not remember hooking the batteries backwards, but the fuse under the motor hood was blown. Took me a long , long time to find that fuse. It ended up being one of the round glass fuses and is a 20 Amp fuse. I put a new 20 A fuse in and it crank good and everything else worked as well (Tilt & choke). I am just wondering now if that fuse is suppose to be a 20 Amp fuse or smaller, because it looks like the wiring is much smaller in diameter than a wire for a 20 Amp fuse. Can you tell me if that 20 amp fuse is the correct fuse for my motor?

That orange wire that I spoke of in my OP was for the from the electric motor connection at the bow of the boat. I do not use an electric motor 'cause I have a gas kicker on my stern. Thanks for your help. My motor is cranking good now, but will be looking for your answer if you know what size fuse is the appropriate one under the motor hood. I bought the boat used a few years back, abd the previous owner may have changed that fuse in the past with the wrong one.
Thank you, pvanv

 

[iggyw1]

HAPPY EASTER!

 

[km1125]

According to the parts diagram for that motor, it is a 20A fuse.

 

[iggyw1]

According to the parts diagram for that motor, it is a 20A fuse.

Thank you. It sure seems like that wire is much to small for a 20A fuse, but I guess not if it shows the need for it in the parts diagram. I will leave it in there. Actually, now that I think about it a little, if the wire was too small, the wire probably would be damaged instead of the fuse blowing, right?

 

[km1125]

What can get confusing is the ampacity of a wire vs the recommended wire size for a given current due to desired voltage drop.

Ampacity is the maximum current carrying capacity of the wire, and it varies due to the type of insulation the wire has and where the wire is installed. If the wire is alone it can handle more current than if it is tightly bundled with other wires. It can also handle more current if it is installed in a relatively cool place in the boat (basically anywhere besides the engine room) vs being installed in a hot engine room.

For a 20A circuit, here are some typical size recommendations:
8GA for a 3% voltage drop and 20ft run
10GA for a 3% voltage drop and 10ft run
14GA for a 10% voltage drop and 20ft run
16GA for 20A max, insulation rated to 105C and inside engine compartment
18GA for 20A max, insulation rated to 105C and outside engine compartment

 

[440roadrunner]

And remember that on boats you have to figure the ENTIRE length, AKA ground/ negative return, and if there's a common return, other active circuits are affected. Also wire sizing charts for house/ AC power are different than circuits where less drop might still affect the load. A good example is "single wire" alternators. They need MUCH bigger charging wire than older, "multi wire" regulator hookups because the "one wire" is also the "sense" conductor