In the Seafoam Islands, you should surf from Pallet Town to Cinnabar Island, then to Seafoam and when you enter Seafoam, there should be a ladder directly in front of you. Climb up it and their is blaines gym.
If you need to find him to get his pokegear number, visit Cinnabar at anytime on Tuesday and he is outside the Pokemon centre.
Chat with our AI personalities
If you have a Pokemon that has a rock type move, then you can easily win. Rock slide works the best.
On Pokemon Silver, Gold, and Crystal Blaine is on Cinnabar Island. On HeartGold and SoulSilver he is at the Seafoam Islands.
According to the storyline, Cinnabar Island's volcano erupted so Blaine had to move his gym to the Seafoam Islands. If you enter the Seafoam islands, you will see 2 places to go: down an icy staircase, or up a ladder. Going up the ladder will take you to Blaine, going down the stairs will lead you to Articuno On Cinnabar Island, head East to Route 20. Keep going until you come to seafoam islands.
You can battle all of the gym leaders out of order in the Kanto Region. Thus, the perspective of the 15th gym leader will change from person to person. Chronologically, Blaine is the 15th gym leader, and he is in the Seafoam Islands, and is up the first ladder you see when you enter.
They are not in Pokemon HeartGold