AQ125B issues

Total newbie trying to learn. My inherited Glastron 17' boat quit on the water last year. My buddy was able to fish around and get it started again after about 3 hours. It then would not turn off at the dock and he did something to shut it down. Here it is a year later and we are trying to figure out what wiring was messed with last summer to get it started. We determined that the resistor connected to the alternator is bad. I ordered a new one. I seem to have an extra brown wire with a female connector coming out of the same jacket as the brown wire that the resistor connects to. Based on tracing the misc brown wire back to the dash, it appears to go to the temp gauge. I would have thought that due to the lack of travel that misc. brown wire has coming out of the jacket that the temp sender would have been located somewhere close by for it to connect to. For the life of me I cannot find where the temp sender taps into the engine and can't find any picture online of where it might be located on this engine. So a couple of things:

1. Where might the temp sender be locate on this engine?
2. What might have been to root cause of the failure to begin with? If it was solely the resistor, then how was it that we were able to bypass it and get the engine started again without it? Do you think there is something else going on that caused the resistor to go bad, or is it just an end of life thing? After all the boat/engine is 37 years old.

Any thoughts are greatly appreciated. It seems like I have tinkered with some many problems with this boat already and have about 15 minutes of runtime to show for it, lol. Thanks.

Re: Resistor... ???? In line fuse holders ( 2) in the wiring, yes but none of my Volvo Instrument panels wiring diagrams show a resistor... and no I don't have specific one for your engine... I do have several diagrams that are for an unspecified (by engine number) range of 4,6 and 8 cylinder engine. These show fuse holders.

Temp sensor... somewhere near the T'stat housing usually.

.... reread original post Resistor near alternator, not on panel.... Does your panel have a VOLTS or an AMPS meter on it. If AMPS, this is the shunt resistor that allows the voltmeter mounted on your dashboard to read and display "AMPS".... If this burns out, no electricity to engine.