odd motor start problem - aging wiring?

[SimonP]

I've had this problem off and on for a year or two. Its intermittent and I can't figure out when its likely to occur. I'll start the engine - if its cold or its been a while it'll take a few tries. I'll get good startermotor behavior, and good juice from the batteries. Usually it starts. Sometimes, though, pressing the ignition switch will do nothing, except the ammeter needle will fall all the way negative. Sometimes if I leave it a few minutes, it will come good. Sometimes (I think) if I turn the main switch off and on, it will fix the problem (?). I've also got a feeling that the battery begins to sound weak before this fault manifests. It did today anyway.

What might be causing this sudden and intermittent dead short?

I know the starter/solenoid is going to be the prime suspect but I've tested this in the past, and I've even had it out and opened it up.

I've begun to suspect my hi-amp wiring and main switch - mostly 40+ years old I assume. I read somewhere that old Perko main switches can get filled with a green goop- I'm trying to find a new one. My battery leads are looking frayed and green at the terminals. Could it be that built up resistance in old wire might be the culprit? I'm thinking that a motor rewire is in my near future - at least main power wiring.

Could anyone shed light on this issue and/or give me a sequence of test routines. I've got a multimeter and pretty much know my way around electrics.

thanks
Simon

[ndutton]

Simon,

In my opinion at 40+ years it's due for aggressive replacement, working or not. I would spend the time replacing rather than chasing. When you're done the problem will be solved, you'll be good for another 40 years and you'll know your electrical system better than anybody.

Intermittent problems are the toughest to chase down. I wouldn't be so sure the starter is in the clear either.

I practice what I preach. My battery wiring is less than 5 years old and just today I finished connecting the engine end of a new wiring harness, all wires run continuous, no trailer plugs, encased in split loom to keep it separate from other boat systems, all end terminals crimped and shrink tubed, ABYC color code compliant and fully documented. New engine panel is in process and due to be installed next weekend. All this work is preventative, I had no problems. My boat is 33 years old and I'm not waiting for the problems to begin.

[ArtJ]

I had a intermittant condition last season where the starter occasionally pegged the Ammeter
negative without turning the engine over. It turned out that the starter had a bad spot where it was shorting out.
. Replacing the starter fixed this.

[dvd]

Check the terminals on the battery or batteries. Make sure they are not only tight but also make sure the connecting surfaces are clean. Us on of those reversible wire brush battery connection cleaners. I have never had this problem on a boat but I sure have in alot of old cars I used to have.

DVD

[ndutton]

Agree with DVD that good clean connections are important but I don't think it addresses the intermittent massive negative amperage.

You've got a huge short to ground somewhere.

[SimonP]

thanks to all

thanks to all for responses. It's sometimes a difficult decision between preemptive maintenance and the wisdom of 'if it ain't broke....' But clearly something is broke and a lot of other stuff is suspect. So - I'll start with a full power system rewiring and new main switch, as that is overdue, and then see if the problem goes away. If not, the short opn the starter motor seems the next suspect
S

[sastanley]

Simon, I am where you are...my wiring is original too, and my boat is older than Neil's. Good luck!

I am currently planning the 'whole boat re-wiring project', but I am focusing on the engine/charging circuit re-wiring part first. A missing cabin light is not as important as starting/running/bilge pumps/charging circuits.

[ndutton]

Shawn and Simon,

I have drawings available if there's interest.

[thatch]

"find the trouble first"

Simon,
I agree with Neil in that it sounds like a starter problem. A sizeable current draw like the starter may look like a dead short. A good test before tearing things apart would be to check the voltage at the starter (while trying to start) to see if the starter is the culprit.
Tom

[hanleyclifford]

thanks to all for responses. It's sometimes a difficult decision between preemptive maintenance and the wisdom of 'if it ain't broke....' But clearly something is broke and a lot of other stuff is suspect. So - I'll start with a full power system rewiring and new main switch, as that is overdue, and then see if the problem goes away. If not, the short opn the starter motor seems the next suspect
S

SimonP - That term "preemptive maintenance" is a gem and settles the issue better than anything I could say.....spoken like a true platoon leader. Regards, Hanley

[SimonP]

the joys of Minneys!

I dropped in to may favorite store today, and picked up an A4 starter motor for $29 If that weren't enough, they just got a rack of high amp crimp-on connectors, so my rewiring project is off to a good start. Now all I need is a replacement Perko 2 battery main switch- I'm watching a couple on ebay.

Does anyone have an idea of the current capacity/awg? My current (no pun intended) (battery etc) wiring seems smaller than it ought to be, ie 8 gauge. But the boat was built by a German electrical/electronic engineer, who overbuilt it in all respects. Pending advice, I'm going with 6 gauge marine grade.

ndutton - drawings of what - power wiring? Yes please! But note, I have circuit breakers - as well as the perko switch.

SP

[ArtJ]

The primary starting circuit should be 4 gauge AWG

[ndutton]

Simon,

Minney's? Dude, we're neighbors! I cruise through Minney's at least once a month just to keep up on their inventory.

During the refit of my boat I've documented every system. Of interest to your current project might be drawings of

1. Battery wiring stystem
2. Engine wiring system
3. Engine harness
4. Engine panel wiring
5. DC distribution system

My battery wiring is 4 gauge. My opinion is 6 gauge is a little light, at least for the starting circuit. House banks could be #6 without consequence. I think I remember Don suggesting #4 as a suitable size for the A-4 start circuit. According to this marine wiring ampacity chart from Blue Sea Systems 6 gauge wire is suitable for 102 amps (engine application) and 4 gauge is good for 136 amps without regard for lengthy runs and voltage drop.



Getting back to the drawings, my battery system is manual switch only, no combining relay or any fancy stuff. In fact, I'll include it here. Let me know if you want more.
Battery Wiring.pdf
You'll have to rotate the drawing to read it, haven't figured out how to save it right yet.

[tenders]

There are A4 parts lying around at Minney's?

I was poking around there back in November after a 15-year absence.

Based on what looked like a large pile of bizarre inventory of approximately zero value, give or take 10%, concluded that either eBay had wrecked Minney's business by disintermediating them, or that Minney's sold anything of use or value on eBay and left the junk in the store.

What did I miss? I saw nothing related to an A4.

(Their used sail collection looked impressive and might have been useful, but I wasn't in the market.)