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Just jump your alternator to the starter post already.

Soupy sails

Member I
The alternator output and glow plug mods are very worthwhile changes. Do pay heed to Mainesails' comment:

"Please note that I generally advise running the alternator output directly to the house bank, not to the starter as shown here. You can then install an automatic combining relay (ACR) or an Echo Charger between the banks to charge both simultaneously. Doing this will remove the potential for fried diodes via the flipping of the battery switch through the OFF position."

In the meantime or if not going to install the ACR, try to not rotate the battery switch while the engine is running. Each time you do hits those diodes with the alternator output and even though they were rated for it when new, they just aren't that new anymore.

I'd encourage doing the glow plug mod as well, because it is also running a high current 10 AWG circuit through those 35 year old (in my case) corroded trailer connectors. When replacing the trailer connectors with terminal strips, the one near the starter is easy to find and replace, but don't forget that there is a second trailer connector hiding beneath the cockpit control panel.

fwiw - I made up some combined schematics a while ago (example below) and have been finding that the diagrams they were based in differ from how the boat was wired. Most of what I'm seeing does appear to be the 1985 factory wiring so I can't blame previous owners for most of these and the message is to check yours before making electrical changes. When I finish the current fuel system replacement and can get in there with the schematics illustrationon the iPad I will update the electrical schematics and post them.

PM me your email and I'll send you a pdf. There've been some updates since the version shown.
Sure thanks my email is glazier718@gmail.com
 

Tin Kicker

Sustaining Member
Moderator
The wiring diagrams have been updated in the following thread, along with some other helpful resources.
 

paul culver

Member III
Inquiring minds beg to know why an approximately 20 foot run of #8 wire (with a resistance of 0.628 ohms/1000 feet) to the ammeter and back to the battery is such a bad thing. I know I must be missing something because getting rid of this circuit is so popular.
 

Tin Kicker

Sustaining Member
Moderator
It's running the full alternator output through (1) not one but two trailer connectors which have a tendency to develop corrosion (amps times resistance = heat), (2) threatening all the other circuits in the trailer connectors, (3) adds lots of wire potential for hot short circuits, and (4) the charging system is dependent on the ammeter not failing (not common but does happen, usually when you least want).
 

Kenneth K

Sustaining Member
Blogs Author
Like Tin Kicker said......

Plus, it's #10 wire, not 8 gauge.

Plus the problems with the circuit are further multiplied by other modifications. Many have switched from the standard 50A alternator to 70-90A or more.

See where this is going......?
 

debonAir

Member III
The trailer plugs are the real issue, not the wire. But even just the wire (#10 is 1ohm/1000 ft, or 2/100 ohms for 20 ft) plus add about that resistance for each of the two end crimp connectors, will add about 0.06 ohm between the alternator and battery. Charging at 20A, that's 1.2 volts of drop. When you alternator thinks its putting out 14.6V your battery is only seeing 13.4V, so not charging as well as it could. Now add in the trailer plugs, which go through semi-corroded zinc plated contacts and were designed for a few amps at most. After 30 years of salt air, they might be adding more than whole ohms to the equation.
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
The trailer plugs are the real issue, not the wire. But even just the wire (#10 is 1ohm/1000 ft, or 2/100 ohms for 20 ft) plus add about that resistance for each of the two end crimp connectors, will add about 0.06 ohm between the alternator and battery. Charging at 20A, that's 1.2 volts of drop. When you alternator thinks its putting out 14.6V your battery is only seeing 13.4V, so not charging as well as it could. Now add in the trailer plugs, which go through semi-corroded zinc plated contacts and were designed for a few amps at most. After 30 years of salt air, they might be adding more than whole ohms to the equation.
As noted in my blog entry about one of the motivations to re-power our boat, I measured a ten degree rise in temp. at each 'trailer plug' and each did feel warmer than ambient. Also, the total distance for that under-size wire is longer than a straight line measurement because the stock OEM extension harness section had a number of feet coiled up and secured under the cockpit. IMHO it's mostly on Universal/Westerbeke for under-designing the wiring system. This helped lower the price and did result in steady sales to Catalina and Ericson, to name only two, but after a couple of decades or more we are all paying a price for their cost cutting.
 

1911tex

Sustaining Member
The trailer plugs are the real issue, not the wire. But even just the wire (#10 is 1ohm/1000 ft, or 2/100 ohms for 20 ft) plus add about that resistance for each of the two end crimp connectors, will add about 0.06 ohm between the alternator and battery. Charging at 20A, that's 1.2 volts of drop. When you alternator thinks its putting out 14.6V your battery is only seeing 13.4V, so not charging as well as it could. Now add in the trailer plugs, which go through semi-corroded zinc plated contacts and were designed for a few amps at most. After 30 years of salt air, they might be adding more than whole ohms to the equation.
This is the most accurate description of the result of my doing this mod..."When your alternator thinks its putting out 14.6V your battery is only seeing 13.4V, so not charging as well as it could"....NOTE: I installed a volt meter replacing the ammeter PRIOR to doing this mod...this statement is so true and obvious using a voltmeter!!! PAUL: Do the mod!!
 

paul culver

Member III
Thanks for the feedback -- I get it now. So if I jump the alternator to the starter can I just leave the ammeter disconnected? It doesn't look like that circuit does anything else. I'll eventually put in a voltmeter instead.
 

1911tex

Sustaining Member
Please replace the ammeter now...voltmeters are inexpensive...usually only 3 wires in the instructions: 1) Ground to old ammeter ground connection 2) hot wire to key module 3) color choice of VM backlight... Instructions are simple. If a low grade person like me can do it...you will fly! Follow Tin Kickers directions!!! You will be most happy and so will your batteries! Good Luck!
 

Tin Kicker

Sustaining Member
Moderator
You can leave the ammeter disconnected and as 1911tex said, voltmeters are easy & cheap.

But

You will need power to the key switch for the panel.


Ignore the red ovals, as they were for another thread.

 

Aloha313

Junior Member
Aloha...

I appreciate this collective wisdom and guidance, as I’m poised to re-wire the alternator to the H/Bank and swap the ammeter for a volt meter. Opportunistic and necessary for my 1980 E35-2; however, I’m no expert. QQ - are there detailed instructions within the site for this? I have the OEM Motorola 51 alternator, 5424 Universal, ACR, BlueSea 5511e b/switch, new AGM house and starter batteries, and a bevy of colored wires in the harness that I simply don’t know if they correspond to the manual diagram. I’ve already replaced the battery switch to starter wire, but dare not touch the rainbow of harness wires unless I’m confident I know what they serve.

Appreciate any help if offered, and if anyone is on Oahu, I’ll buy the Longboards (beer) for a look over the shoulder. (Not much in the way of reputable marine electricians on island....at least that I’m aware).
Aloha...Jeff
S/V Mauka Makai
 

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Tin Kicker

Sustaining Member
Moderator
Aloha313 -
I know nothing about the 35 so below are guesses and go with anybody else who can offer actual specifics.

My GUESSES are that:
1) You have the same trailer connectors somewhere so that everything previously mentioned would apply to trying to remove at least the heavy red & orange wires from active use.
2) Your boat probably has an equivalent to the orange wire in my diagram above, so that would be changed to the B side of the key switch. If not running new wire for the whole circuit, at least cut the wire on either side of the trailer connector and install a waterproof butt splice to go around the connectors.
3) Remove the existing red fused wire, or as much as you can. Cut a piece and use a fuse same size as original (30A on the E32-3) to go from the alternator B+ post to the start solenoid where the diagram shows the red attach. Or you could get fancy and install a circuit breaker.
4) Next would be removing the ammeter and connecting just about anything in the 12V system to power a voltmeter. The B side of the key switch would work for the + and the bottom post of the tach should already have a number of black wires for ground (-).
 

racushman

Member II
HI guys, question for this group related to this thread...

A while back I realized the alternator on my M25 had a bit of a "wobble" in it when running. When I took things apart I realized that a prior owner must have operated it without the mount screw tightened down... and hence the mounting bracket had an elliptical hole in it... which I of course took as a good reason to upgrade the alternator. I decided to replace it with one that Catalina Direct offers for the M25... a 100 amp internally regulated unit for $165... seemed like a good deal.

Installation was pretty straightforward BUT the terminals on this Prestolite unit are somewhat different than the outgoing one. Should note that my boat has had the ammeter replaced with a voltmeter in the panel, however the wiring is a bit of a dog's breakfast and ultimately needs Maine Sail's full rewiring.

For clarity, the new unit has connections for POS, NEG, and two separate AC Taps

I have connected it as follows:
- POS the the starter POS terminal
- NEG to ground (isolated ground unit)
- Tach to AC tap

BUT MY QUESTION: on the old alternator, the Purple wire that appears to power the electric fuel pump also has a Y in it that is also connected to a alternator terminal labeled EXC. New alternator does not have a EXC terminal. Can anyone guide on what to do? Remove it?

Appreciate any help.
 

Kenneth K

Sustaining Member
Blogs Author
The old Motorola alternator did require an excitation circuit. It's the purple wire that gets powered whenever the key switch is turned on. If you don't have a terminal for it, I'd guess you don't need one on the new alternator. But I would probably call the folks at Prestolite and ask them.

I think the wobble problem is due to the wrong size bolt. Ericson used a 3/8 inch alternator bolt, but the bracket actually needs a 10 mm bolt to keep the alternator from wobbling. See MaineSail's post about "alternator bracket upgrade" for further discussion.

If you end up eliminating the excitation circuit, I'd probably get rid of the Y connector and just butt-splice the purple wire to the fuel pump wire.
 

racushman

Member II
Thanks Ken, appreciate the insight on the EXC connection. I'll just remove the Y on the Purple wire and see how that works.

Also appreciate the point on the 10mm mounting bolt. I had not caught that. But I had noticed that even the new alternator did not mount up in the bracket as snugly was I would like --- that must explain it.

I'll report back with results.
 

racushman

Member II
Follow up to my 11/1 post...

New alternator works great without the Purple wire connected in any way... just butt spliced it to go direct from the panel to the electric fuel pump.

Also, Ken was exactly right about the bracket needing a M10 (10mm) bolt instead of the 3/8" one that I removed. Completely eliminated the wobble.

As a final confession, I also learned about isolated ground alternators in this process. The old unit I took out had no black wire and just grounded itself through the mounting bracket. I didn't realize the new one had an isolated ground and thus required a specific black wire to the boat's grounding system. I learned this by starting the engine and finding the alternator wasn't charging. Which I then corrected with a ground wire, only to find that I'd already blown the voltage regulator. Corrected with $80 at the local auto electric shop. Fortunately my ineptness is easily remedied with $$s.
 
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