Excessive heat at starter motor terminal - wrong metals?

[Shearwater]

Noticed on a very calm day, when applying power to the starter, a whisp of smoke from the + terminal of the starter motor, and nut was too hot to touch within 5 or 8 seconds...highly dangerous me thinks. There's a stainless steel washer next to the starter, then the h/t lead and then a mild steel nut. Presumably the excessive heat is caused by poorly conducting metals reducing the current flow to the starter ? If so what should I use - all copper or brass ? Could there be any other explanation? Thanks in advance.

 

[oldsaltoz]

It all needs cleaning, pull apart and remove anything that is not shiny including any oil or grease.

Resemble and smeare a bit ov Vaseline over it ti restrict moisture and aie entry.

This will cool things down a but.

Avagoodweekend......

 

[MoodySabre]

The electrical connection should not be affected by the washer - the nut on the thread should be the main route. Something is burning out because the resistance has got too high. Besides cleaning every part of the connection up I would look at the where the cable is crimped into the connector, Perhaps there is corrosion in there and it is the strands of the cable that are giving up. For me it was not the cable but the wire from the positive to the solenoid that corroded and then burnt out.

You could dispense with the washer - it serves no purpose under the cable end.

 

[DannyB]

[ QUOTE ]
You could dispense with the washer - it serves no purpose under the cable end.


[/ QUOTE ]
The usual reason for a washer to be there, is that someone has fitted a terminal with the wrong size hole, ie too big. Agree the cause of the heat is bad / dirty connection, if you are stripping it down to clean, it would probably be a good idea to replace the stainless washer with a brass one, better conductivity IMHO.

 

[Refueler]

Usual reason is bad contact..... it may be enough to let starter work, but the high ampage and load causes heat and smoke through any corrosion / grime that's there.

Take apart connection, wire brush it all up clean and shiny ... bolt up dry and clean. Once bolted and checked by starting ... a smear of vaseline over top to delay repeat corrosion.

 

[2Tizwoz]

The problem may be as it at first appears - simply a loose dirty connection - if however the terminal is on the starter solenoid it would be as well to consider that the problem may be that the contacts are in poor condition and the solenoid cap with contacts needs cleaning up internally or replacing. This could be shown up by the starter turning over the engine more slowly than it should and further down the road by a clicking starter which doesn't turn the engine at all.

 

[lw395]

I recommend a serrated star washer to give sure metal to metal contact. Stainless is not the most reliable for connections, brass or steel plated with zinc, tin or similar. Discard any nuts or washers that are corroded. Assemble with copper grease to keep the water out. I have some special metal grease I use for this, I think it may be best to recommend something like Holt's 'No Crode'
ebay item no 200317250765
As others have suggested, contacts and cables may also conduct heat to this point.

 

[Shearwater]

Thanks all; the crimped h/t lead is much larger than the dia of the starter terminal & all was very grubby. An interesting aside - I had to use the old nut because it is Imperial and I have no way of sourcing a replacement and as I've never dabbled with electrics before I don't have a tin of useful nuts and washers. Indeed, I must find a 5/8 inch spanner before I next twiddle the injectors as the nearest metric equivalent just isn't good enough.....so old engines keep going but we run out of tools and nuts ??

 

[ADLS]

Look out for odd nuts and bolts at boat jumbles etc, buy good quality adjustable spanners. Buy some next size up metrics and file them down to size. Mechanical/motor engineers have job specific spanners that are bent and tweeked to get into tight corners etc that would otherwise mean stripping off lots of components.

I still carry a very usefull box of nuts, bolts, thingme jigs and whatsmecallits as the boat is 1930s and stuffed full of old gear. Always remove any usefull bits before you bung anything away.