Detroit 8V-71's are very common commercial
engines. What you have is a marinized truck engine in fact. Look in some of the trade
magazines and you can get some pretty inexpensive prices for a rebuilt starter ...and get yourself a spare while you are at it. At a few hundred bucks each they are not all that expensive...unless you go to the dealer to get ripped off by him. $300 is a fair price
. You can bet the marine
engine dealer is going to ask $500-600.
You starter cable should be 2-0 cable at minimum for that engine. Your start battery should be an 8-D start battery and not a deep cycle 8-D. Starter motors do burn up but the first thing you do before replacing a starter is to make sure your battery terminals and cable terminals are absolutely clean. This includes your ground cable which is just as important to have clean as the hot cable, and should be led from your starter directly back to your battery or negative buss terminal...and then to the battery. The crimp terminals can also go bad...check for resistance across them...there should be none.
Voltage drops across bad or dirty terminals is the major reason starter motors go bad. When the voltage drops the current has to increase in order to crank with the same horsepower. (volts x amps = watts) and when you increase the current, it heats up the coils...burning them up. Wires that are hot in temperature also have more resistance which aggravates the problem
Continuous cranking or cranking with a weak battery can also damage or burn up a starter motor.
A starter motor that cranks when cold but not when hot could also be an indication of a loose terminal that simply needs to be tightened down..I have had that happen.
Your start battery may also be getting old. They are generally good for roughly 5 years if they have been maintained and never abused.
When you do clean your terminals, spray on some battery terminal anti-corrosive. Scotchbrite pads are excellent for cleaning the terminals.