Who's marine chevys are they? Are they late model with roller lifters?
Can't tell you what's in them with out knowing which ones they are. Gm
makes them all but there are a number of variations depending on what year
they are and who they were being sold to.

When you say "build" do you mean hop up or do you mean complete rebuild?
Cause a long block core is only worth a couple hundred bucks so I would
consider other choices. Big blocks or a diesels would be a better fit.

The factory small block marine cam is a decent cam. Not sure you could do
much better. Add an aluminum manifold and a holley 700 and you might get it
near your 280hp. You could bump up the compression a tad but not much given
today's octane. Also if you underprop it a bit that might help. Hard to
get a lot of torque out of small block anything.

Here's my mouse motor but I'm probably only getting 280 or so hp out of it.
I started with a 4 bolt truck core. Aftermarket pistons, pink rods,
edlebrock intake and heads, holley, crane roller rockers, stainless
exhaust. It has the factory marine roller cam but the rockers are 1.6
instead of 1.5. I had a aftermarket cam but it cost me low end. Went back
to the factory cam.

http://home.earthlink.net/~jamesgangnc/ebay/boateng.jpg

wrote in message
ups.com...
I have a 32' Luhrs Sportfisher. Currently with Chrysler 318 engines.
I have 2 Chevrolet 350 4 bolt marine engines, one standard, one
reverse rotation. I would like to find out what spec. and what parts
I need to build these engines to 280 to 300 hp on carburators. The
boat weights 17000 lbs. It is my understanding I need foot lbs. of
torque more than rpm. Anyone know if there is a guide or book? Anyone
with information. Thanks in advance.