a friend is looking for a boat with 350 Horizon. What are the differences between the two?

I went on merc site and printed the definitions of both and it is wriiten the exact same thing!

Thanks!

i think the horizon is the same except it adds closed cooling.

Yes.

Go back to the Merc website and look at the Inboard section.
It shows the horizons with quite a few upgardes,
Three year warranty, top mounted starter, different oil pan, the inboard version has closed cooling standard not sure on the I/O version. I do know the inboard version has Titaniam Spark Plugs for longer service intervals sort of like the Cadillac NorthStar Engine. The Horizon Series was started for Inboard use. I didn't realize they offer a sterndrive version. Good question on your part!
VeeCat

sorry about the spellcheck or lack of........

The top mounted starter must be something new. The one's I've seen were regular mount. Maybe it's just for inboards. I sure like my top mounted startes on my Formula. Deb change one in 15 minutes, all I did was hand her the tools.