i'm stumped
 

friend if mine has an '85 blazer and he keeps killing positive batery posts and starter solonoids any ideas would be awesome. thanks

sounds like the starter is dragging.or it has an internal wiring issue, like the brush wires are hitting the case, or field magnet is going bad

Check all grounds and make sure that both the engine and starter where they go together are clean.

this is the third starter that has done this in about a month i didn't install any of the starters so i dont know how clean it is i dont know why i didn't think of going through all the grounds first i really appreciate the pointers guys thanks

jedder check out this thread here sounds like it may pertain to you with the grounding issuehttps://www.dieselbombers.com/chevy-gmc-6-2l-6-5l/99122-slow-cranking.html

Try unhooking battery cables on one battery when the truck is not in use and only hook them up before starting and having to use. c if tht helps narrow the problem down..ive heard of this on a few of them

there is two neg wires from your batteries the one going to the engine should come from the driver side batt and go up to the top of the block near the intake manifold. the engine end of that wire tends to oxidize inside of the wire creating heavy resistance. i would start at that.

Is the starter bracket/brace installed?

If the starter has no rear brace installed it may be moving and grounding out the battery cable on the block or frame when starting,depending on how that cable is positioned on the starter solenoid terminal and if the cable has any insulation missing near the end.

thanks to you all he has since moved away but i will pass along your advice and have him check and hopefully solve the issue