# Mercury Classic 50 - Blowing Fuses



## Kier (Sep 20, 2016)

I think I bought a real winner. Previous post was regards to lower unit with no oil and destroyed it. I got the new lower unit in and took it out to the lake for a weekend. The first day had no issues. The second day half way through I started having issues with it blowing fuses every time I took it out to run the limb lines. The motor ran like a champ all weekend except the fuse issue. I noticed that I lost tilt / trim at the forward controls when the fuse was blown. The motor kept running till I shut it off. I would then replace the fuse start it up and run the lines again. By the time i got back, I had another blown fuse. I went through 5 fuses that I happened to have on hand. I tried not using any accessory power on two runs no difference. I have since done research on the web and the best I can gather is there is short some where in the tilt / trim wires? Should be a fairly easy job to replace wires from the motor to the forward controls. The only other weird thing I noticed is my Lowrance 5 fish finder was registering anywhere from 13 to 16 amps depending on my motor rpms. Could I have an undersized battery that is blowing fuses? Some advice would be helpul before I go and replace wires till I find a short.


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## Kier (Sep 20, 2016)

Side note, I did replace the ignition switch after the original one broke when trying to push to choke.


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## Kier (Sep 22, 2016)

Looked over the wiring tonight and the forward control wires look good till it hides underneath the deck. I did find one blue wiring cord that comes out of the control bundle that had lost its covering. It was also low enough to be in the water if I forgot to run the sump. I taped those all up and hung them from the roof of the compartment with a zip tie. I am going to buy a stock pile of fuses and put them in the boat and see what happens next time I go out. Most likely wont be until the spring till it happens.


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## Kier (Sep 23, 2016)

I winterized the boat tonight and took the battery out. It was in a plastic case. It was an closed cell battery, not a lead acid battery. Everywhere I read said the rectifiers need to use the battery as overflow and should be a lead acid battery to handle the charging rate. Hopefully I did not ruin the rectifier on the motor.


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## richg99 (Sep 24, 2016)

Everything that you said points to an intermittent short. 

I doubt that the bare wire caused all of the blown fuses unless it was making contact with bare metal. Now, if the bare wire was in saltwater...then...it might have been the culprit.

I know that smarter people than me know how to use the little 12 volt circuit tester, like this one.... https://www.ebay.com/bhp/12-volt-circuit-tester 

I'll bet you find it and correct the issue and she will be fine.

richg99


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## Kier (Jan 30, 2017)

Rich, you were right. I got the boat of storage to get it ready for the spring, and I was still blowing fuses. I went through 9 fuses isolating the issue to the forward controls. I found out the following. 

I isolated it to I was blowing fuses when I shifted from neutral to reverse. I took the forward controls off the mounting bracket and had them laying on the seat. I could not recreate the issue with the side panel off. As soon as I went to bolt the unit back to the mounting bracket the fuse blew. It must be shorting to the metal of the boat. I do not see any bare wires in the unit, but I can only see the ones that are not hidden behind the throttle mechanism. I ordered a 12volt 20 amp Asdomo Circuit breaker so I dont keep burning through fuses. Any advice on how to find the short? How hard is it take apart the older (1985) Mercury forward controls?


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## stinkfoot (Jan 30, 2017)

I bought A 1977 Merc 402 off a guy in WA. He had bought the boat of an old guy at the lake and I think this motor had sat at the cabin being barely used. I paid 500 bucks, Unknown to me ALL the wiring was rotten and I mean COMPLETELY.... Luckily for me I had a parts motor(1975). Replaced a few wires and swapped out a few bits and this motor runs like a champ. The paint is still shiny.... Will post a daylight pic. Mercury insulation for that era really sucked badly. My advice is replace what you can and see if it helps.


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## richg99 (Jan 30, 2017)

Well, I may be the least knowledgable in this area...but..one thing that you said sounds really strange. *" It must be shorting to the metal of the boat"*

That might imply that your negative cable is grounded onto the main hull. On an automobile, they do ground the battery to the frame. On a boat, especially an aluminum boat....that is a no, no. Electrolysis could easily occur.

So, the first thing that I would do would be to double check, at your battery location, to see if they did bring a ground wire to the main hull. If so, remove it.

I REALLY think that the issue is more in the controls. As the last poster said, it could easily be that the insulation has rotted off of wires inside of the control, and every time you put pressure on the wire bundle, one of the wires touches another wire. 

Sounds dicey, but...what have you got to lose at this point? Take a picture of the inside of the control, remove one object at a time, taking pictures along the way, and expose those hidden wires. Replace with new ones if any appear brittle or cracked. 

Alternatively, buy a used control and replace it. 

I hope more knowledgeable members will jump in with a better suggestion.

richg99


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## Kier (Jan 30, 2017)

My circuit breaker arrives Thursday. I will do more testing to isolate the issue then. 

I did not know that boats have grounding issues.


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## richg99 (Jan 30, 2017)

*"I did not know that boats have grounding issues."*

Yeah, a lot of people think they are like a car. But, cars don't spend lots of time floating in the water. 

Around some marinas, electric current leaking into the water from improperly grounded vessels have destroyed lower units and more.

richg99


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## Kier (Jan 30, 2017)

I did some research and it sounds like the metal of the boat is always grounded by the engine being bolted to the boat. Then the internet said to not use it because of corrosion.


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## Kier (Jan 30, 2017)

Well I think I found it. I took it apart and where the control arm pivots there is a group of wires that feeds the controls in the arm. One of the wires was bare where it had pinched. I taped them all up and put it back together. I dont think the previous owner had the pivot screw tight enough. Which allowed play in the arm. I will know more later this week when i get my 20 amp circuit breaker. Which hopefully means no more being stranded.


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## richg99 (Jan 31, 2017)

Good news. Richg99


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## Kier (Feb 2, 2017)

It was 25 degrees here tonight, but I had to know. I went out and cut out the old fuse holder and put in the new Asdomo circuit breaker and re-mounted my forward controls. I mounted my forward controls on wood so it cant short out unless it does it internally. I am trying to fix the issue every way possible. 1) Install circuit breaker so I dont run out of fuses and get stranded. 2) Taped the bare wires hopefully fixing the short. 3) Isolated the controls from the boat via wood. After installing the circuit breaker the tilt came back to life. I put the motor in and out of gear several times and it still worked. Hooray! I usually go out early March and will report back if everything goes well then. The Asdomo circuit breaker barely fit under the cowling. So if you are looking to use this on another outboard make sure you have the room for it before purchasing.


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## richg99 (Feb 3, 2017)

Hooray! I love it when we fix things, starting out with no real understanding of what was wrong.

Sounds like you isolated the issue; repaired the faulty lines, and can go out with confidence in the Spring. I understand doing things in bad weather....just so you don't have to lie in bed and wonder.

regards, richg99


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## Kier (Feb 26, 2017)

Had a real nice 70 degree day and took out my boy and enjoyed the boat. Water temp was 50 degrees. No issues with blowing fuses. Going camping and fishing in a couple weeks. Will put it through the torture test then. I replaced the battery with a new group 24 lead acid battery. I am still getting readings of 16 volts on my fish finder though. Any advice on that issue?


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## richg99 (Feb 26, 2017)

Is the voltage reading from the fish finder only? Did you test the output with a separate voltmeter?

A 12 volt battery won't put out more than 12 volts.

If you get that reading while the engine is running, you may be seeing the output of the engine's own alternator. Even that shouldn't be 16 volts. 

If you are just seeing the erroneous voltage reading on the fish finder, and a separate voltmeter shows 12 volts with the engine turned off.. the fish finder is faulty. I wouldn't worry about it. You can buy a separate permanent voltmeter for under 10.00

Richg99


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## Kier (Feb 28, 2017)

My old fish finder Lowrance elite 4xhdi and my new one Hummingbird helix 5 both showed 16volts. I have not tried testing with a multimeter. I know the older mercury motors dont have a regulator to stop charging the battery when full. They just assumed the battery would regulate it. I am just concerned it will fry my fish finder.


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## richg99 (Feb 28, 2017)

* I am just concerned it will fry my fish finder.*

At 16 volts, I'd be concerned also. Suggest you just call your Fishfinder manufacturer and see what the maximum voltage is for your unit. 

I'm sure that you could google up some kind of cheap voltage regulator. Your FF probably only draws 3 or 5 amps. I'd check an auto supply store and see what they have. They have to deal with 12-volt batteries and alternators/generators.

richg99


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## Kier (Feb 28, 2017)

I contacted HumminBird via email. The automated response said they would get back to me in 2-3 days. I looked through the manual and the only over voltage information I could find is under troubleshooting. 

Problem: The control head loses power at high speeds

Possible Cause: If the power output of your boat's engine is unregulated, the control head may be protecting itself using its over-voltage protection feature. Make sure the input voltage does not exceed 20 volts.


Well I don't I have that issue, but my boat engine is unregulated. Maybe it is not an issue at 16volts.....???? I will post what I find from the HumminBird.


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## Kier (Mar 1, 2017)

I got the email back from HumminBird.

This is what they said.

"Thank you for contacting Humminbird. We appreciate your interest in our products. The power input is 10.8 to 20VDC for the HELIX 5 SI GPS."


So I assume the 16 volts should be fine and not damage the unit?


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## nccatfisher (Mar 1, 2017)

richg99 said:


> Is the voltage reading from the fish finder only? Did you test the output with a separate voltmeter?
> 
> A 12 volt battery won't put out more than 12 volts.
> 
> ...


Most fully charged 12volt lead acid batteries at static will show 13.6 volts


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## Kier (Mar 1, 2017)

I have a 1985 Mercury 50HP and it charges the battery when it runs. Unlike the newer motors it does not have a regulator. So it sends a charge to the battery even though the battery is fully charged. At full throttle the motor produces ~6amps of charging. The newer motors have a regulator that stops charging the battery when it is fully charged and turns the extra charge into heat. It is possible to buy a regulator for these older engines but I am trying to avoid it if possible.


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## richg99 (Mar 2, 2017)

*Most fully charged 12volt lead acid batteries at static will show 13.6 volts*

You are 100% correct. I should have clarified that 12 volt batteries do not produce 16 volts....but..they do show more than the nominal 12 volts after a charge.

Thanks richg99


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## nccatfisher (Mar 3, 2017)

richg99 said:


> *Most fully charged 12volt lead acid batteries at static will show 13.6 volts*
> 
> You are 100% correct. I should have clarified that 12 volt batteries do not produce 16 volts....but..they do show more than the nominal 12 volts after a charge.
> 
> Thanks richg99


Gotcha, I would be a little worried if it was showing 16V. Especially if he made any long runs with it. That could fry a battery or some sensitive electronics.


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## Kier (Mar 3, 2017)

Just as you charge a 12 volt battery and the volts raise to 13ish, the unregulated charging of the older outboards is causing my battery to raise to 16volts while it is charging. I checked with an eletrical engineer friend of mine and he said if the specs for the fish finder are for 10 to 20volts and it should not matter if it gets 13 or 16 volts supplied. I am going to run with it and see what happens.


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## nccatfisher (Mar 3, 2017)

Kier said:


> Just as you charge a 12 volt battery and the volts raise to 13ish, the unregulated charging of the older outboards is causing my battery to raise to 16volts while it is charging. I checked with an eletrical engineer friend of mine and he said if the specs for the fish finder are for 10 to 20volts and it should not matter if it gets 13 or 16 volts supplied. I am going to run with it and see what happens.


Do as you wish, when you start over charging a lead acid battery it really starts generating gases (hydrogen sulfide) all it will take is a random spark and you have a problem.


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