Replacing an alternator

jrhhtk1 · Post by **jrhhtk1** » Fri Nov 19, 2010 6:23 pm

My alternator went out and I got a new from Cat for my '82 Model 3208 engine. Is there anything special about wiring it up since it now has a voltage regulator included in it. The + and - wires on top are easy but I have another wire and not sure where it goes??? Jeff

IRGuy · Post by **IRGuy** » Sat Nov 20, 2010 11:35 am

Jeff... I am certainly not qualified to give you any advice about engine electrical systems, but I would go back to Cat and ask for an installation wiring diagram, or possibly go to a local engine shop and have them show you how to install what you have.. I recall reading somewhere that there are distinct differences in how to install different alternators!

mikehedb · Post by **mikehedb** » Sat Nov 20, 2010 1:48 pm

I don't know what it is in your case, but I know some of the older style alternators required a 12VDC wire for an exciter. On some of the newer alternators that is internal and the extra wire is not required. I also am not qualified to provide this type advice, but when I switched to the new style alternator on my gas engines I had to abandon the extra wire.

CB35 · Post by **CB35** » Sun Nov 21, 2010 5:23 am

I will take a look this morning on my boats. One has internal the the other has external regulators. Have you figured it out yet? My recollection is two wires go on one of the posts. My recollection is the external had four wires. You can find the external regulator and follow the wire or wires from the regulator to the alternator. Just don't hook that one up. I believe it is that simple.

jrhhtk1 · Post by **jrhhtk1** » Mon Nov 22, 2010 12:12 pm

Thanks to all. The alternator I got from Caterpillar was the new kind with an internal exciter and voltage regulator. Basically all I had to do was tape off the 2 wires (+ and -) coming from the external VR (that I just bought) and connect the 2 main + and - that go to charge the battery. Getting a good solid 13.8 to 14 volt charge all the time. Thanks guys for helping out. By the way, I also replaced my starboard raw water pump while I was getting dirty. The new water pump on these 3208's is a Jabsco 6400-0004 with 1-1/4" outlets and takes a 9" pulley. The older style (in the Cat book) had 1" outlets and a 7" pulley but evidently didn't put out enough water to cool the engine properly.

CB35 · Post by **CB35** » Tue Nov 23, 2010 4:51 am

Hi Jeff, Got a question. Was your boat repowered with the Cats or did it come from the factory with the external regs and the smaller water pump. All the 35B's I have looked at had the internal voltage regs and the larger pump. Just curious as I often look at boats for folks. Usually 35B though. Thanks

jrhhtk1 · Post by **jrhhtk1** » Tue Nov 23, 2010 6:25 am

Charlie, from what I know, the Cat 3208's on my boat are original equipment. I know that the original alternators are the old style with external VR's. The raw water pumps appear to be original because when my port side went out and I took it off, it looked about 28 years old!! So I'm thinking Cat must have changed to the bigger pumps sometime around then. To answer your question though, yes, these appear to be the original engines. Thanks for all your help.

jrhhtk1 · Post by **jrhhtk1** » Tue Nov 23, 2010 6:27 am

Hey Charlie, I'm guessing we have the same engines. Is there any more wiggle room on the 35B than the 33 when it comes to working on the port side water pump or the starboard side alternator?? I worked on both and I'm 6'-2" and 215#. When I got through, what wasn't bleeding was pretty bruised up!! Talk to you soon.

CB35 · Post by **CB35** » Tue Nov 23, 2010 12:22 pm

Yes you can crawl around the front of the motors and lay next to the engines. I am 6'2" but I cut down to 190. I would like to get to 185; but with Thanksgiving and Christmas I will have to wait until next year. My 3208's are T's at 300HP. All the 35's seem to have 300HP from the factory and the bigger water pumps. I checked the book and it looks like 1Z1 to 1Z819 had the external regs. Thanks for the info.