alternator ground melting

Hi All,
Today I went to start my 1986 2001, first time this year, and while the engine was cranking over, the alternator ground wire started melting/smoking. I saw the smoke and stopped cranking it over, checked the connections and tried again and the ground continued smoking and the starter would not turn over the engine, but you can hear it engage and hum until I let go of the key. I got this boat running 4 years ago and I haven't had any issues with charging/wiring/starting. Battery's were replaced last year and kept on a battery tender. Three years ago I replaced all the battery cables and installed 2 battery's with a perko switch. What should I look at? Is the alternator bad? Maybe the starter?
Thank you,
Shawn

There is no external voltage regulator, the wire runs from the alternator body to the engine block.

I can't recall having an engine with a alternator ground wire.   They ground thru the mounting points.
Is it possible the alt output has been hooked up to ground?    That would make it smoke!

Sounds like the main battery ground is bad where is it connected to the engine? Take a set of jumper cables and connect the black to the battery negative and then to a good connection on the engine . If it cranks normally its the ground cable.

Shawn,
I suggest not getting new parts just yet. You mentioned you checked voltage. What voltage are you getting both without cranking the engine and also when cranking? I'm having a hard time understanding how there's still current running through that ground wire when all the other wires to the alternator are disconnected. Disconnect that ground wire too. I also suggest having the batteries load tested. When you are trying to crank the engine, what setting is the Perko switch on? Both?

Please do as Michael says, its electrically valid advice.

Shawn,
It's looking more and more like you have a starter problem. Ken provided some great info on a new one. You could also open up you existing and see what's going on inside. I still very confused on why that ground strap on the alternator is taking a beating. Have you had the engine running after you installed the Perko?

I changed the starter, starter solenoid and I upgraded to 105 amp alternator and it is starting with no problems. I jumped the old starter and all it would do it come out, but it wouldn't spin, so I'm sure it was the starter.

Thanks for all the help.

Shawn