1998 Arctic Cat 454 4x4 (Water in Engine)

[jfkkhi]

Hi,
I am new to this forum and also new to “ATV”.
I just bought 1998 Arctic Cat 454 4x4; according to last owner it wasn’t used for last 3 years.
I tried to change the engine oil, noticed coolant water inside and mixed with oil. Now I changed the oil and filter and still can’t start.
Any ideas? How fix this water and oil mix issue?
Thanks

[GRIZZLYWIZARD]

Could be a few things, but whatever it is, it isn't good.