Is this too much of a challenge?

[Laveral]

I have 8 PCs in my group. Six of them are 4th level and two of them are 3rd level. this is the way the group looks:
Half-elf Paladin 4
Human Cleric 3/Wizard 1
Dwarf Ranger 4
Human Fighter 2/Sorcerer 2
Gnome Alchemist 4
Aasimar Inquisitor 4
Dwarf Rogue 3
Human Druid 3

I have an encounter set up for them that is a young Brine dragon that is CR 7. Im just wondering if this is too tough of a challenge for them?

Thanks.

[Sarcon]

color spray! I think it will be a good challenge, just don't hit them with anything to severe afterwards

[wraithstrike]

Using one monster is never good when there are that many players. Either the monster will be too strong or not nearly strong enough. It is better to use more monsters that are of a lower level.

Maybe a 2 CR 6's or 3 CR 5's

[Fergie]

I don't think it is really too tough, but the encounter might be a disappointment. For example, it is fairly likely that a full attack from the dragon will kill a PC, however, if they were to color spray the dragon, it might well be stunned, and get killed before it gets to act.

How about 2 young white dragons? Or a bunch of half-dragon mephits, or something like that? Anything BUT a 8-vs-1 gangbang.

Edit: Can you tell us a little more about where and how this encounter is supposed to take place? Is this a boss monster? Will the PCs be in it's lair? How about 3 half black dragon ooze mephits while a dozen zombies smash their way up from the ice underneath the parties feet?

[Laveral]

They are going to check out a wrecked ship near a waterfall. Behind the waterfall is the dragons lair. Well actually you would have to swim underneath where the water is falling to go into the dragons lair. On the cliff side however is a cave entrance that is 30 feet from the top of the cliff. My purpose for the whole thing is clues to lead them to the next agenda, the dragon will just be standing in their way to get to the next clue and a couple nice pieces of treasure.