1988 volvo n131 charging system problem

hi,1988 volvo 131 ran boat for first time yesterday.after 15 minutes out came in turned off motor ,got ruck eng wouldnt start just click.took home put battery on charger it shoewd real low.but at ramp would pwr.tilt.ok.1/2 hour after no start tried turned over and fired up shut it off know batts .good .alt when checked with test klight showed good pwr from starter good grd .but terminal marked d t where resistor wire hooks up wouldnt light up test light unless lead put on positive showing it as ground.is this rt?also noticed voltmeter on boat inop.shos power and grd at wiring on gauge.ordered new gauge would this preventfrom charging?thanks for the help ernie also if alts damaged what wouldve caused it.as spare i have shows same thing.please excuse typos fighting 1 yr old for computer while typing.

Re: 1988 volvo n131 charging system problem

First thing you have to do is get a Volt/Ohm meter. Every place has them, then learn how to use it.
Then with the engine running at around 1500 rpm, check the voltage directly at the large orange or red wire output wire on the alternator. It should be reading just above 14V.
Also check between the + & - terminals of the battery, they should be seeing the same thing, are they?

Re: 1988 volvo n131 charging system problem

thanks for the help got it working after replaced alt.