I have SmartCraft guages. The speedo, which is gps, keeps popping the fuse button. The problem is significantly worse when engine rpms get up over 3800 or when I have the battery switch on 1 or 2 instead of "both". With low rpms and having the battery switch on "both", the button does not pop out.

Would I be asking for trouble if I increased the amps on the fuse button to see if it keeps working? That paticular fuse button powers the speedo and fume detector.

Don't increase the breaker size until you know what the expected current draw is and what the real draw is. If the boat came wired as-is, I'd guess you have a faulty gauge, faulty fume detector, a bad voltage regulator, or a bad circuit breaker. A short would not be likely, based on your description.

Thanks for the reply. Would disconnecting at separate times the speedo and the fume detector and then seeing what the reaction to either component being disconnected help me narrow down the problem?

I agree. Unless you added something to increase the current demand, and are sure that the wire can handle the extra current, I would not advise installing a larger breaker.

Yes it would. If you disconnect one and the breaker doesn't pop then I would suspect that device to be a problem and go ahead and replace it.

And you might try disconnecting both and see if the breaker still pops - it could be in the wiring...

If your breakers aren't hard to get at, swap your tripping breaker for another of the same amperage.

If swapping stops the tripping, then you know the breaker was bad. And especially if the other load starts tripping the old breaker.

If it still trips, then you know you have an issue that needs attention...

Volt/Amp/Ohmmeter.

Disconnect items individually, reconnect with meter set to amperage in-line temporary,a dn find out what the gauge amp draw is. Gauges should draw very little power, even a GPS speedo. This should help you track down a fault, or prove no fault. Also, if the total amperage draw below the fuze rating is popping the fuze (first thing to check for), you know the fuze is faulty.
Even cheapo meters measure up to 10 amps DC. The "nice" one at Wal-Mart is a good piece. One of my 2 is certified at work, so it is dead on accurate (aviation work, any readings for reccord must be from certified tools, meters are checked for accuracy every 6 months). I'm sure the other one would cert if I took it in. $20 plus the extra clip-leads from Radio Shack.

VOM/DVM (volt-ohmmeter, Digital voltmeter), your best friend.
Get one and buy a set of leads with aligator clips on them (Radio Shack, among many other places).

I unplugged the fume sensor in the engine compartment and ran the boat for an hour or more and did not trip the breaker. I will leave it unplugged for a couple more trips out to see what happens. Right now its looking like a fume sensor related issue.