[C38] Electrical Problem

[Tom T.]

Hello Rich,

I think you may have already answered your own question about possible 
problems with the harness going to the engine control panel.  The 
original wiring system was dangerous when the boats were new and only 
get more dangerous with time.  Eventually the harness can fail causing 
possible dire consequences.

Not only are the plugs on the original harness prone to failure but the 
long length of wire going from the alternator to the panel and then back 
to the batteries causes a voltage drop which greatly reduces the 
vessel's ability to recharge the batteries.  Owners have been known to 
pay for expensive alternator upgrades which only magnify the fire 
hazard.  A new harness will be like having a larger alternator without 
the expense and also without the extra load on the engine.  There have 
been reports of alternator mount failure with larger alternators adding 
to the dilemma.

You do  NOT need a whole new engine panel harness.  You only need to 
bypass the heavy current lead from the alternator to the panel.  Use a 
heavy inline fuse at both the alternator end and the battery end and use 
heavy marine grade wire to make a new alternator lead. Marine grade wire 
was not used in the past because it was rare and expensive but marine 
grade wire is tinned so it is more corrosion resistant and easier to solder.

Since you will not be having a large current going to the panel any 
longer, you can still use the existing wires if you want to for running 
a volt meter which has almost no load so it will not be fire hazard or 
cause failure from corrosion arcing at the connectors. It may be a good 
idea to make a whole new harness but the main thing is to get the 
charging circuit out of that harness in any case.  Even if you make a 
new panel harness, the charging circuit will no longer be part of it.

A volt meter is one additional advantage of the harness upgrade.If you 
replace the amp meter with a volt meter, make sure it is a marine unit.  
The automotive units will look and work good for a short time before 
they fail due to the salt corrosion of marine use.  As a side note, if a 
volt meter does fail, it will not kill the charging circuit like an amp 
meter will so by changing to a volt meter you will also increase 
reliability and safety there also.

The difference in the wiring connection of the volt meter as compared to 
the amp meter is that the amp meter was a series fed meter going back to 
the batteries while the return leg on the volt meter just goes to the 
panel ground which is adequate since there is very little current 
through a volt meter.

I wrote a Mainsheet article some years ago detailing the harness upgrade 
but I can't remember what year or month.  Maybe another member with 
website access  can direct you to the article if it is archived.  In a 
nutshell, the main accomplishments of a new harness are:

1,    Shorter and less resistive charging lead from the alternator to 
the batteries for more efficient charging.
2.    Elimination of failure prone harness connectors.
3.    No phantom electrical loses from corrosion in the connectors or 
amp meter.
4.    A volt meter installed in the engine panel in place of the 
original amp meter.  A volt meter will give you better information of 
your electrical system.  For instance, if you had a battery with a 
broken and shorted cell plate, an amp meter would possibly still show a 
good charge rate while a volt meter would show you had low voltage 
caused from a problem that needed attention.  Often an amp meter will 
give a false sense of security..

Good luck,
Tom Troncalli
Former owner of #95 and now in lurker status
770-356-2223





On 6/7/2014 7:38 AM, fleet2001 at aol.com wrote:
> Guys,
> I need some electrical advice.  My boat "Merriconeag" hull# 138 has 
> about a
> 2amp drain in the engine compartment.  I think I should replace the 
> trailer type
> harness with a bus bar. Also, possibly replacing the ammeter with a 
> volt meter.
> I have to switch the engine battery switch to off when I shut the 
> engine off or
> the battery will drain power. Help.
> Thanks
> Rich Grassia
> fleet2001 at aol.com <mailto:fleet2001 at aol.com>
>
>
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