TOPIC: 72' 800 Rectifier and wiring.

I am new to outboards and this one is my first.

The wiring on this motor is brittle and chard in places. What kind of wire is it? It does not seem to be copper. Is it aluminum?

I got this old moter running today, but it is not charging the battery. I seem to be getting over 200 V AC comming into the rectifier, but less than 2 V DC coming out of it. Can I get away with an automotive rectifier as a temporary replacement?

Also there is a switch under the key on the throttle that I have not learned the function of yet.

Any help would be appreciated. I am trying get it in the water tomorrow.

Daniel

Hi, Daniel, the wiring is braided copper which is more flexible and resistant to vibration than your standard stranded wiring. Yours probably looks all green & corroded, so it'd be hard to tell what it really is!

Best thing to do is to cut the wiring back until it's good n' solid material, then splice a new section in with an uninsulated, solderless butt-splice crimp connector. Then solder for best electrical connection.

Cover the splice with a single layer of electical tape, then cut a hunk of shrink sleeving long enough to overlap and completely cover the splice. Shrink 'er down, make up the end-connection in a similar manner, and you're good to go!

If you can get marine wire to use as a replacement, more the better, but it's rather expensive. Standard automotive wire will still give a good service life in your older Merc. Use a size of wire similar to the existing wiring.

Your rectifier is shot. The stator, when unregulated, puts out a horrific amount of AC voltage, and it's possible to exceed the insulation resistance value of the windings and blow them out, if you rev the motor up with an unloaded stator. Not much fun, that!

Any full-wave bridge rectifier with a rating of at least 10 amps can be used, it's good to have one with a higher voltage rating for reliability. I picked up some 35 amp, 50 PIV (Peak Inverse Voltage) rectifiers from an internet electronics supply house, in nice metal enclosures, about the same size as the little "square" rectifier commonly used on later Mercs (at least the ones that don't use a voltage regulator).

The output on your Merc's charging system is unregulated, although generally not capable of putting out more than 10 amps. Certain batteries like gel-cells and deep cycles don't like the high terminal voltage (sometimes up to 16 V or more), some electronics don't care for it, either.

A simple marine starting battery or regular old lead-acid car battery usually get along just fine with the old-fashioned charging system. Or turn on the running lights if the voltage is going too high.

If you think you'll have the need for a regulated system, one of the newer-style regulator/rectifier assemblies can be retrofitted, but they're not cheap.

Just to get it running, you can use a very inexpensive Radio Shack rectifier, under $5.00.

www.radioshack.com/product/index.jsp?parentPage=search&summary=summary&techSpecs=techSpecs¤tTab=summary&cp=&custRatings=custRatings&features=features&accessories=accessories&productId=2062584&origkw=rectifier&support=support&kw=rectifier&tab=support

Lousy picture of the back only. Doesn't show the 4 terminals. You'll note the Merc rectifier only has 3 terminals, that's 'cause it's grounded thru the case. On the Rad Shack rectifier, you'd ground the 4th, (-) terminal via a short wire to either the mounting screw, or a convenient grounding point. The 2 yellow stator wires hook up to the (~) terminals, and the red (hot) lead to the (+).

You just have to figure a way to mount it, since all it has is a center hole for a mounting screw. Easy enough to tap a screw hole in the cowling or other accessible metal part.

You'll have to change the "round-eye" connector lug on the stator wires to a female "spade" type, no biggie, especially if you're re-doing the wires anyway.

The switch under the key, have no idea! Maybe a pic of the control box would help.

Hopefully that'll get you going, have fun on the water!....ed

Thanks for the help. I took a couple of pictures this morning and checked
some of the paperwork I got with the boat. The boat is a 67 Crosby and it
looks like it may have had a 62 700 on it before the 72 800. The controls
may be from that older motor.

Daniel

Also there is a switch under the key on the throttle that I have not learned the function of yet.

Choke switch?

My pics did not load above. The choke is pushing in the key. I don't see
anything happen with this switch.

Oh okay, that's the "dead man switch" or emergency cut-off. There is a lanyard that hooks onto the switch and your belt or life jacket. If you should get thrown out of the boat (or out of your seat, really) it will cut the motor off to keep the boat from screaming across the water un-manned! Definitely a great safety idea/item IMHO.

Thank you for the warning about the unloaded voltage Ed. I was going to try
it in the water without the rectifier, but will go get the part first now.

I have not had it over 1000 RPMs yet, so hopefully the alternator is still OK.

I got a RadioShack rectifier as was suggested. As I as about to install it
and I was checking how far back I had to cut to get good wire to connect onto,
and both wires became completely disconnected at the top. I do not think
there is any way I can connect the wires now. Judging by the condition of the
wire there I think the damage continues into the windings. Looks like I
need new stator windings now.

If the stator is already destroyed, is there any further damage that could
be done if I just run it off the battery to check out the motor on the
water?

Daniel 77 wrote:

If the stator is already destroyed, is there any further damage that could
be done if I just run it off the battery to check out the motor on the water?

Hard to see how it could hurt it now! I've never heard of anyone catching their stator on fire due to bad wiring or blown rectifier, so I doubt anything's gonna happen.

Of course, goes without saying, better Safe than Sorry, I'd run it without the cowlings installed and carry a fire extinguisher (should have one on the boat, anyway!).

BTW, it looks like there are more than 2 wires coming out of the stator, how many are there (or is is just an Optical Cornfusion??).

You might want to make sure than none of the stator wire remnants are touching each other, since the stator is still capable of generating voltage, you wouldn't want to accidentally make a short circuit.

HTH.......ed

I tried to remove the stator but found you need a special tool to get the flywheel off. There were two wires going to the stator, but they were so badly degraded that it just looks like a mess of strands. I took a chisel and cut the wire off close to the stator and have hopefully kept them from touching. Below is a pic before I finished removing the bad wires.

I have a large marine battery charged up and a chase boat to tow me back if the battery goes down faster than think. I will launch it in two hours.

If you pull 2 opposing bolts on the flywheel, you can use an automotive harmonic balancer puller (or equivalent) to remove the flywheel.

Use 5/16" fine-threaded Grade 8 puller bolts of appropriate length.

When you reassemble, clean the flywheel bolts, apply a drop of Loctite Red on each bolt and torque to approx 24 ft-lbs.

G'luck on your run.........ed

Daniel, My charging system isn't working either. I use a marine battery, charge it up before going boating, and it's lasted 3 days easily and recharged in less than 1/2 hour when I got home. If your motor starts quickly (no long cranking) and if you don't have a big load of accessories like radios and stuff, I think you'll be fine.

Ed, thanks for the tip on flywheel removal. I need to remove mine to replace the timing belt and thought I'd need to buy a special puller.

Thanks for all the help everyone. I got out on the water and back without a fire or being towed. Some wires will get replaced before I go out again. After I took my wife out for a ride, she agreed that it is worth putting more time and effort into.

Daniel