Installed new boss guage style receiver in my boat. it will not power up. 12 v supply, and ground are good.

I'm not experienced with the boss, BUT..... the symptom suggests that you have wired the receiver into a circuit which:

1. has too low a curent rating [not enough amps] for the receiver device, AND....
2. is protected with a SELF RESETTING circuit breaker.

IF that is the situation, then the OVERLOAD caused by the too heavy receiver is causing the circuit breaker to "TRIP" and cut off the electric power in the circuit.

Self resetting breakers work by having a bi-metallic strip inside which causes the strip, when overheated by an overload, and in bending, OPEN the circuit, cutting off the power. This reduces the risk of an electrical fire!!!!!

When the bi-metallic strip cools enough, it RE-CLOSES the circuit, turning the power back on UNTIL the overload causes to to trip again.

This is a safety/fire protection issue, AND you need to take your vehicle to a QUALIFIED [CERTIFIED preferably] vehicle sound shop where a qualified TECHNICIAN can troubleshoot the issue, and probably will either find a more powerful supply circuit, OR....

ADD a new, adequately sized wiring circuit to support your sound equipment.

What this issue sounds like is that YOU have installed a sound system/device which needs MORE POWER than your existing circuit can safely provide!!!!!!!!

Be SAFE, get PROFESSIONAL HELP!!!!

Check you have a real good ground at the the guage and the tank sensor. Most likely (black) wire. 12 volt systems on boats are often ground problems.

fuses that look bad are.
fuses that look good , can be , in FACT bad.
DMM, (flip to low ohms)
fuse reads 0 ohms, its good
fuse reads infinity its bad.
if fuse is good check for 12 at the radio power wire.
the radio must be ground do work, is it?
some radios have a separate ground wire (black) is it grounded?
post new radio make and model and can answer with 100% accuracy.
im a retire ET.
DC to daylight. experances.

If the new harness / parts are listed for use with this model GPS, it should work - unless you have miswired something. Double-check your work. Make sure all connections are made up tight. Pay particular attention to the ground wire. Relying on the boat to pass ground it not reliable. Look for damaged or cut cable from power source and transducer. You may wish to troubleshoot with a meter or a test light to be sure power is available at the GPS. Good luck!

Best bet is to take your boat to a qualified Marine Audio dealer (generally not a boat repair shop or marina), or to a good quality Car audio store that is insured to work on boats (separete insurance usually).
When it comes to boats, you need lots of power and speakers.
First thing to do is make sure what you have is properly installed. Then determine what is "distorting" .. is it too much base, purely volume or what.
Most boats we do (wakeboard style and river boats) we do: 40-75 watts RMS per speaker 4-6 speakers in boat 1 10" or 12" sub with 200-300 watts RMS Tower speaker if requested with 75-125 Watts RMS per speaker

Disconnect all the speaker leads and then hook one speaker (a new, known to work speaker) up directly to the radio using a short (6"-12") piece of speaker wire. Does that speaker work then?

You have a good idea but with the transformer you may not have enough amps to get full power out of your bulbs. Be sure you have a good ground at the trans, These bulbs are not as bright as you might be thinking with out the proper reflectors. You might try a sealed boat trailer type of light w/ a clear cover. Check out wally world, boat supplies, or a simi trailer parts supply for a good tag light.

I'm assuming that this is a wooden or fiberglass hull (not a boat person). Ground for the radio needs to be either through the chassis (any existing screw or mounting stud on the radio will do) or via the manufacturers installed wire. That takes care of the NEGATIVE.

The Positive wire from the battery or from a switch must be attached to the correct input wire to properly power the radio, you can probably connect it to the memory (hold) input (which will drain your battery if left connected long enough) but that is not the best place.

Did this help? I am assuming that this is a new radio and you have the manufacturer supplied wiring diagram. If you do and my suggestion did not help, I could sure use a look at it to further advise you.

ok,
connect your positive 12v of your amp to the remote part of your amp. youll see it will turn on.

12/29. I actually figured this one out myself after reading posts concerning parking brake over rides. It turns out that the Boss BV9055 will not powerup if the pink parking brake wire from the units wiring harness is not grounded. Once I grounded that pink parking brake wire the unit did power up.