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70hp Johnson J70elcos blowing fuse.

F

FrankMa

New member
There is an inline fuse in a red wire near starter solenoid that keeps blowing. Motor won't crank, primer won't click when I push key in. Any idea what I should check?
 
I see the other thread about the 90 horse motor. My problem is not intermittent. It blows as soon as I put a fuse in. The rectifier on this one is a little round thing with 2 yellow wires and one red one. Could it be the rectifier or do you think a short in the control box?
 
I see the other thread about the 90 horse motor. My problem is not intermittent. It blows as soon as I put a fuse in. The rectifier on this one is a little round thing with 2 yellow wires and one red one. Could it be the rectifier or do you think a short in the control box
 
I disconnected the 3 wires for the rectifier and it still blows fuses. Is the control box hard to take apart and put back together? I don't see any rubbed wires between the control box and the solenoid.
 
What have you done to the motor recently? What made this start?
I've attached a link to the wiring that should be correct for your motor. It says it for 70 HP from '78-'84 thogh. Your fuse is just to the left of the starter where the red wire connects to the two wires tht look to be red/blue. The first thing I would do is disconnect the big plug on the main harness that goes from the control box and connects to the motor under the cowling. Disconnect that and then put in a fuse. If it doesn't blow, I'm pretty sure you need to replace the ignition switch. If it still blows, I'd make sure the red wire is connected to the properlocation on the solenoid. The red wire should have power at all times. Then make sure the red/blue wire is connected to the correct location on the box with all of the electrical connections. Right were the wires for the rectifier were. If the ignition switch is in the control box, they can be a monster of wires, cables, springs and all sorts of crazy stuff in there. All the wires have to go back exactly rounted the same way you found them or they won't all fit and/or they'll get pinched.
 
Just 3 screws and the control box can be split to examine the wires,-----Nothing is going to fly out at you.----Easy job in my opinion.
 
Thank you gentlemen for your replies. This problem just showed up suddenly after trailering the boat to a small lake where we have a vacation rental. When I turned the key nothing happened. The battery is fine. The tilt trim works. I I took the cover off and found the blown fuse. There is a direct short somewhere. I have only a few tools here. I have been able to get the motor to start by jumping the solenoid. I may wait until I get home and split the control box. If I don't see any obvious bare wires I'll replace the ignition switch. Thanks again.
 
OK folks, here is my progress so far. If I unplug the big red connector the fuse blowing stops. So I took the control box off and split it and found it to be easy as Racerone said. I removed enough components in order to facilitate examining the wires and I couldn't find any that looked bad in any way. So is the ignition switch the next likely culprit? I see they are only about $30 on this site. I have a multimeter but I am more of a barnyard mechanic than an electrician. If there is a simple test I can perform on the switch with my multimeter I could try it if the instructions are simple enough for an electronic moron.
 
Here's what the back of your ignition switch should look like:
omc_0508180_addl_1.jpg
 
So,
S is start Yellow/Red
C is choke Purple/White
A is accessory Purple
M is ground Black
B is battery + Red
M - threaded hole - STOP shuts off motor - Black/Yellow
I'd start by disconnecting all wires from the B terminal except for the original RED wire. I'd also trace that wire and make sure nothing is tied into it. That's a direct wire from the battery. It has 12 volts at all times. If there are several wires on that screw, remove them all and only connect the one that has 12v. I'd disconnect all wires from the B terminal before plugging that big 1" diameter plug back together, and find the one that has 12v and connect that to the B terminal by itself. Next step would be to check the M ground termina and make sure that the wire is in good shape and the screw is tight.
Lots of boaters, as they add accessories to their boat, they attach the power and ground wires directly to the ignition switch. If/when those accessory items go bad or they aren't wired correctly, they will cause that fuse to blow. I hook gauges, lights, stereo and other very low draw accessories to the A terminal and have inline fuses for lights and stereo. Bilge pumps, livewell pumps and other accessories with larger amperage draws, and depth/fish finders, I hook directly to the battery with inline fuses and switches.
Good luck with tracing down the problem. With the age of the motor and control box, the colors on those wires might be hard to figure out. Sometimes, I very carefully cut away a little bit of the insulation on that 1" diameter cable that goes from the control box to the motor where the wires aren't as faded. But be sure to wrap that up really good with electrical tape to keep water out.
 
Well Mr. Old Salty Dog, your very first sentence in your first reply turns out to point to the true root cause. There turned out to be only one fat red wire going to the B terminal. So for the heck of it I took all the wires off the ignition switch and it still had the short. So I figured the problem had to be between the ignition switch and the motor. Now, back to your question what did I do to the motor recently? I did nothing to the motor but I did pull out the carpet, pull up the plywood deck in order to access the seams and rivets from the inside. My boat is a 38 year old Grumman side console and I have owned it for 36 of those years. It had developed a number of leaks in the rivets and seams so I wanted to apply some Gluvit to plug up the leaks. This was the first trip out with the boat since I did the Gluvit treatment and put the floor back in. That main wire bundle between the control and the red connector is much longer than necessary and nicely encased in a durable plastic semi-flexible conduit. Well it turns out a loop of that conduit is trapped under the edge of the plywood. Rather than pull up the whole floor again I am going to pull up that section of carpet and carefully saw out a small section of the plywood. Heck, I may have even run a screw thru that conduit when I was screwing the floor down. I need to borrow a little saw from work in order to perform this delicate operation. So hopefully I can get this self induced malfunction corrected tomorrow. I am 66 years old and I guess I won't stop doing stupid stuff any time soon. However I learned a lot this past week and I won't make the same stupid mistake twice. Now I know how to disassemble a control box and how the ignition switch is wired. I will report back when everything is shipshape again.
 
Fantastic! I'm 63 and I manage to keep doing stupid things too. Last time I replaced the plywood flooring in a boat, I ran 2 screws completely thrugh the hull! Pulled the screws out, squirted some clear silicone in the holes and ran the screws back in!! Had that boat for another 5 years with no leaks!! We'll never stop making mistakes, but with the help of good friends and websites like this one, hopefully we'll just keep findin ways to correct our mistakes. I hope you and I never stop learning new things!!
Let me know what you find.
Good luck!
The fish are waiting for you!
 
Everything works now. Not only did I run a deck screw thru the conduit. I ran it right thru the red wire right to ground. That fuse had to blow the instant I put that screw in. All I have to do now is replace the section of conduit I had to cut out and wrap everything up nice and add some strategically placed zip ties. Then re-glue the little section of carpet I had to pull up. Vacuum up the mess and make sure everything is all nice and neat. Thanks for all the advice and data.
 
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