I would not buy a dedicated meter to measure 8 amps.
You should have something to monitor
your batteries. Current
two choices IMO are Smartauge and Victrom BMV602. Both are likely to exceed the cost of your solar
They do slightly different things and Smartgauge won't count amps.
You have a 37 foot boat and I expect you plan to expand power systems int the future.
I would get Smartgauge now and see if something better for amp counting comes on the market in the future. I think the BMV602 is fast reaching is "sell by date" from a technology standpoint.