Wiring Harness

If you want something that's pretty foolproof as far as wiring, you could get a 1 wire Delco alternator. The 1 wire only has the output terminal and you would hook your big orange wire there. The sensing and excitation wires that go to your present alternator just get taped off and hooked to nothing

It's self exciting and senses output voltage right at the alternator.

It has some disadvantages like you need to initially rev it to about 1000 rpm's for it to excite itself every time you start the boat, then it's good till the next start even if you go down to idle speed.

For a boat with no big loads it works fine, quite a few people here have used them A lot of boats came with them as standard equipment over the years including some OMC's
If you have a big honkin' stereo with a half dozen giant speakers the 3 wire would be better   

You'd have no need for a diode either

Maybe some other people will weigh in with their opinions.

DB electrical, the same place as the link in the previous post sells them too, for about the same price as the 3 wire. You'd want one with the same size pulley you have now..

Keno,
Are you 100%sure that is the correct alternator? I appreciate your help!!! Thanks!!!

Well, those pictures give quite a bit of information

First I'm sure it's a Delco Remy 3 wire alternator mostly because it says Delco Remy on the back.

Second   that's not a marine alternator because there is no spark arrestor screening on the back of it. The marine ones have the screens in front (behind the fan) and in the back. The ones in the back are plainly visible and yours doesn't have any back there. Somebody probably replaced it sometime in the last 32 years.

It's an explosion hazard.

You can find a marine rated Delco Remy 3 wire in the link below at a reasonable price.

As far as finding a diode, I'd look for a 5 amp diode at an electronics website or on EBAY they're easy to find. They're a buck or two each.

Did you have to pull that wire off to stop the engine?

Usually when a diode dies you get an open circuit and in this case an open circuit on that wire wouldn't have prevented shutting off the engine. If everything melted and fused together, then you'd have problems shutting it off. It looks like somebody's homegrown diode job from what I can see.(Looks like somebody crimped a spade connector onto the diode wire that's visible if I'm seeing the second picture right)

I'd get the marine alternator as part of fixing this.

Kinda a long answer for "where can I find a diode?"    and maybe not what you wanted to hear

link   

How about a picture of the alternator (from the rear) or if there's a tag on it with the brand that would be helpful too.

A picture is worth a thousand words and a it's lot easier to see just what you need

shierh wrote: My dad who we call The Word, is an ammeter fan. He wanted me to re wire in that manner. dads 88 but I can say he has forgotten more than most will ever know. Aerospace engineer that actually did write the book or at least a chapter in an engineering manual.

Steve,
It sure sounds like your dad is a very intelligent person. Gain as much of his knowledge as you can. There sure are times that I think back and wish I had listened to my father more than I did.

shierh wrote: Im also guessing that if your boat is set up with amp meter instead of volt then you would notice a significant discharge when key is off, am I correct? I changed mine to volt meter when I re did the electrical. Now I am second guessing the decision.   Mine would be easy to re wire however since I used a positive and negative buss bar under the dash.

I think I'd call it more of a minor deflection on the meter that you may or may not even notice.

You done it now though Steve, you mentioned the word ammeter and left the door wide open for Pete to show up and proclaim his undying love for ammeters

Im also guessing that if your boat is set up with amp meter instead of volt then you would notice a significant discharge when key is off, am I correct?
I changed mine to volt meter when I re did the electrical. Now I am second guessing the decision.   Mine would be easy to re wire however since I used a positive and negative buss bar under the dash.   

shierh wrote: So after all this it has nothing to do with Back Feed. Nothing to do with draining battery or anything else, its a simple fuse?      Thought everyone used a breaker, guess OMC guys wanted to be different.   Make more money selling fuses I guess.

The thing is just a fuse.

Now if you look at a PCM wiring diagram they use.....................nothing on the alternator output.

Straight from the alternator to the output side of the main breaker, no protection for the alternator output wire if it was to become grounded between the alternator and the breaker,other than the wire being sized to handle full alternator output.

And if you have rectifier diode issues like mentioned a while back, you can drain the battery back through the alternator overnight. The flowpath is from the battery to ground through the rectifier assembly and the amount of current depends on the failure. The OMC fuse will do nothing to stop this slow discharge.

And also depending on alternator brand and style, you can have issues where you turn the key off and the engine stays running especially with a 3 wire AC Delco swap in place of a different alternator. It backfeeds through the excitation line and the coil stays powered till you rip the wire off or you choke it till it stops or if you're feeling real lazy, you let it run till it's out of gas

An external diode or a properly sized resistor comes with many of the AC Delco swap kits for this reason.

I think I'll hang it right in plain sight at the workbench as a reminder of how good the internet can be at spreading bum dope.at times.

Can you return it?

Well, the mailman left me a package today.

My OMC part showed up so I figured I'd figure out what's inside the ugly blob of epoxy.

Took the multimeter and it conducted in both directions then also put it in the supply to a 12 volt light in both directions and the light lit up both ways so....................ain't no diode in there

Now I gotta decide what to do with this thing. I could keep it hanging around, I could use it as OMC meant as overcurrent protection for the alternator output wire or I could cut the wrapping off and see why OMC and now Bombardier charged a fairly outrageous list price of about 55 bucks for it.

They're a whole lot cheaper on EBAY after nobody has bought one for the last 20 years or so and it's taking up shelf space.

So Steve,(Williams) since you have one.......................

It's time to pull that off the alternator and test it to see if there's a diode in there and solve this mystery.

Here's a link to testing a diode with a meter.

In a nutshell, hook the meter leads up one way and then reverse the leads and compare readings.

If there's no diode, you'll have continuity in both directions

If there's a diode, you'll have continuity in one direction and an open circuit in the other.

Depending on part numbers, OMC calls some of them a fuse and lead assembly and others a diode and blocking assembly.


link

Prestolite ALK-6222A or 6222AY alternator. Parts book show that as a fuse and lead assembly. Fairly ugly assembly but it’s there to protect. My engine has it. 60 amp fuse.

Keno, good explanation.

So it seems it is not a necessary component, only there if the internal diode within the alternator fails.   So if the internal one fails would not the back up one get pretty hot? doesn't seem that an insulated diode would be able to cool down.   
Can diodes leak back just a little and not completely fail?   if so then i see how this component could be useful.