SLP - sorry, but I forgot to tell you scroll down to see the post when you click on the link :-)

SLP
The camshaft you are running is about the same as the stock marine cam. You should see a big increase if you go with the camshaft that I recomended. Should be fun!
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE

Dennis,

So what are your thoughts on the aftermarket exhaust, such as imco, or stainless marine vs stock ?

Just curious..........thanks

If you want the most power from a high horsepower small block engine you need something better than the stock exhaust manifolds but there isn't much on the market for the SB.

A small block, with only 350 cubic inches, doesn't create as much exhaust volume as a big block with 454 cubic inches. An engine with 104 more cubic inches creates a lot more exhaust volume that needs to be extracted from the engine. Look at it this way, if a big block needs an 800 cfm carb and the small block only needs a 600 cfm carb (on the inlet side) the same holds true for the exhaust side.

The stock mercruiser manifolds on a 350 do not create as much backpressure as the stock mercruiser manifolds on a 454. There is a much bigger improvement in performance when changing the big blocks exhaust than when changing the small blocks exhaust.
The four inch exhaust (or even 3 inch) from the exhaust manifolds to the transom (or even through the prop) is huge for a small block engine, not so huge for a big block engine (2 1/2 is large for a car exhaust!).
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE