Like Doug warned, I received a young boa once with mouthrot and RI, as the two can both be the result of bad husbandry.

The mouthrot was treated as Doug explained, and it cleared up very quickly. I used Betadine instead of peroxide, but both work. I took the snake to the vet for the RI, and he prescribed Baytril. That infection cleared up quickly as well. Boas are tough snakes, and due to their larger size are more easily treated. I have no doubt your snake will be fine if treated asap.

And keeping the snake warm and hydrated helps make the recovery all that much easier for the snake. Treating the snake but keeping it at 75 deg does not do much. Make sure it has access to an 80-90 deg range. A soak in very shallow 80 deg water for 5 minutes will hydrate the snake better than a water bowl.