Repower I/O Qs.

[Hammerhead]

My 165 inline 6 finally croaked. I dunno if it's just a head gasket or worse but since it's over 30 years old I figure it's time to repower. Question is..just replace the 6..go with a V-8 ??? or is there a inline 4 available? Any tho'ts?
Power wise the setup now is OK...I'd like better economy...would a inline 4 be any better?

I also figure a whole engine/outdrive package will what I'll end up doin;....anything other than dumpimng 40 Gs in a NEW boat.