Your amp should not have a 50 amp fuse at the battery. It puts out 300 watts RMS (continuous power). The fuse at your battery should match the one that is on the amp itself. Your amp is overheating and there is a fault, possibly your speakers are wired to present too low of an impedance to your amp. Disconnect them from your amp, and use an ohmmeter/multimeter and measure the resistance load. It should not be lower than roughly 2 ohms. Depending on whether you bought dual 2 ohm or dual 4 ohm subs, that could be the heart of your problem.
If you bought D2 subs, you can get a 4 ohm load per sub with each sub's voice coils in series, and then parallel them together to get a 2 ohm load at the amp, which is perfect for your amp. Or you can wire each sub's voice coils in parallel, so that they're 1 ohm each, and then series them together at the amp for a 2 ohm load. The first method is simpler. Be sure that you haven't wired each voice coil in parallel (1 ohm per sub), and THEN also wired both subs in parallel to the amp (1/2 ohm load). That would definitely send your amp into protection mode, probably before it would have a chance to overheat. This is another reason why you should not have used a 50 amp fuse under the hood. If for whatever reason, the fuse on your amp doesn't blow, the amp is getting way too much current for it to handle, because of that 50 amp fuse under the hood.
If you bought D4 subs, you have a problem. If you've wired each sub's coils in parallel (2 ohm per sub) and then wired both subs together in parallel at the amp (1 ohm load) you're presenting too low of a load to your amp. Again, this will overheat your amp and send it into protection mode, both of which are what you're seeing. You never want to have two D4 subs with an amp that only handles 2 ohms, because you can't get a 2 ohm load with two D4s. You're stuck with 4 ohms or 1 ohm. 4 ohms cuts your amp power in half, 1 ohm cuts it off completely.
If you know for sure which way you've wired them, then you now have the information to tell you whether you've done it incorrectly or not. If you're not sure, first disconnect your subs and measure the resistance as I described in the first paragraph. If your amp is seeing a 1 ohm or 1/2 ohm load, there's your problem. If you see a 2 ohm load (subs are wired correctly after all) then you may have a bad ground connection, or your amp is bad and needs to be serviced/replaced.
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