The red in the bilge looks nice!

I personally wouldnt run those on anything performance oriented, and even the stock Mercs were having reversion issues with the OEM manifolds of similar style. You don't need big bucks headers. Keep an eye out for good Stainless Marine manifolds, or even EMI Thunder has long riser tubes and they'll even weld in the bungs for you. The Imcos are still good manifolds that you can sell for a chunk of change, but not for your application.

that manifold you should be able to drill and tap for a 02, might have to do in one cylinder depending on how the manifolds are made, I had to do a in a single header tube on lightnings but worked fine

Well she is back together and started her up and boy does she sound better. Much crisper sound and the throttle response is faster. I am taking her up to Tahoe tomorrow for a last run of the season and see if I can beat my 58 mph with 90 gallons of fuel!

Started saving for some headers too.

Thanks everyone for your suggestions on doing a leak down test. She ran really well yesterday on Lake Tahoe. I did not make any changes except for changing the jets to lean it out more and a little more timing. The acceleration is greatly improved but even with the improvements I still cannot move past 5k rpm with a 3 blade 19 pitch. I have finally come to the realization that a NA motor on a lake at 6,377 foot elevation is going to be tough with a heavy 30 ft boat. Since I finally have a solid motor do I add headers and re-cam for some added power? I am planning on getting headers for next year. Unfortunately I cannot do a blower as I have no space for pulleys. The only other option would be a turbo setup, and not really excited at the cost/exhaust setup? I can't go crazy on a cam but really would like something to turn 5700-6k to take the power band out farther at the top. It was pretty darn cold too. Couple of pics of having the lake to ourselves.

so, blowby no mas?

None, was perfect except my oil filter still leaks LOL. Even tried a Moroso one and it leaks the same as K&N. Everything seems to be good now with the motor. 5k rpm run for about 15 minutes oil pressure was 75 lbs, oil temp was around 200 and exhaust temp around 1300 degrees with the water temp showing 105-110.

Best way to gain power is to replace the atmospheric pressure you have lost...or more of course.

Keep an eye on those adjustable timing chains, after one season and even with red locktite on the 3 bolts mine came loose broke the cam dowel and advanced itself 4*.
Threw those ****ers in the garbage

without boost you are going to need lots of torque, did not pay lots of attention to your setup, but big cubic inches, a pair of good oval port heads etc..

Thanks for responses and I do agree at this altitude boost is needed but the boat is not setup for a blower with no space for blower pulley's and a turbo is not something I want to get into or seems easy to find for an enclosed engine. This motor ,even in blowby mode, made a ton of torque (see dyno sheet) and currently running 088 heads with just a little work done. I am going to keep my eyes out for a nice set of used headers and think about having a new cam ground. I can already tell my wife wants a newer boat I can't "f" with, maybe I can have a hot rod and a family boat?

As far as the timing chain my Gen IV block takes a Gen VI timing chain and that is what Summit had in stock in a double roller at the time (This really confused me when putting it together LOL). Still debating on retarding the cam I have just to see if it makes any difference.