I am a strict do it yourselfer with a fully furnished shop at my disposal and a good knowledge of all things mechanical.
One thing I havent done yet is build an engine. I am wanting to learn how to build high performance marine engines preferably in my spare time. Any info an this would be great.

Thrill, what kind of info are you looking for? There are alot of good books on the subject out there, but the best thing to do is hookup with someone who has experience building them.
Marine engines are a bit different than car engines, I have alot of experience with both aspects. Im hoping to get back in the business soon myself. Id be happy to offer any help i can.

A few books i can rcommend to you are by HP Books

Big block Chevy Marine Performance
Smll Blk Chevy Marine performance
Performance engine Blueprinting

These are just basic info manuals , but they do offer some good help.
But as i said the best thing is to work with someone with experience.
VinMan

YOu say in your SPARE time ? YOu must not own a boat now if you have spare time !

Yeah my boat takes up most of my spare time Ile just have to make more time

That's something I'd like to tackle myself some time.
I haven't built an engine in many years. But I still remember how it's done.
There's nothing like hearing it fire up for the first time.
The whole time it's cranking over you're trying to remember if you did everything right.

Torque all bolts till your teeth barely clench, and if it doesnt fit get a bigger hammer let me know if you need any other help but this should cover 99% of your questions.