Not sure what Ign your running. You may have said however you really need to make sure and check it at full advance. How does it sound on the lake at WFO? Normal.... Good luck. Just start checking things off as you go through them. Just an easy way to rule things out. Carb? - 4 barrels opening? You could even have a bad plug wire that's perhaps hitting at an idle but not beyond. Did you do a quick plug check to make sure they all look near the same. No wet ones. Keep us posted.

Somthing is not right here, your propeller slip is 20%. If Bob set you up with a cam in a 489 you should have at least 500HP. You must be leaving out some details, maybe you have a timing issue, not enough fuel, timing gears not lined up, plug wires crossed. The compresion numbers look ok, when the engine is cold they never read the same.

Here is a site that may help you figure out prop slip http://www.rbbi.com/folders/prop/propcalc.htm

55 on the speedo is what I used to see as well then you get humbled with the gps. I ran 42 with a 330. Loved the way the boat looked but it was heavy. It has a sink, galley, built in cooler and such. I think there is more speed there but you will have to work the prop.

I know what you mean about "happy" speedo's. Oddly enough, the one on my Baja has always been pretty much dead-nuts on. I never got the illusion that I was running in the 60's - I knew I was slow the whole time! :eek:

Are you running stock Merc exhaust manifolds, or something else? I am putting together a very similar 489 with Air Gap, etc. I have a brand new 850 Demon that belongs to my BOL. I was toying with running it, but everything I have been reading indicates that it will be too big for my combo at the ROM's I plan to run (around 53-5400). I have read that the Demon's are wet flowed for their ratings, rather than dry flowed like the Holley's. If this is true, then an 850 Demon would flow considerably more air than an 850 Holley. Others may chime in as well, but I think your build would be better suited to an 800 or 830 Holley.

I'm running 496 exhaust manifolds. BTW, Bob Madera was the one who recommended the 850 carb for my engine.

Well I don't think the 850 is too big but typically a STD 800 is called for but bIgger is better(; play with the props and see what happens one thing at a time. See what ur timing is at full out. Try 34 deg if ur running premo fuel. Next step would be to lighten her up a little.

I found the original review of my boat by powerboat mag in 1989. It lists top speed of 53 @ 4700 rpm with a 19 pitch Mirage prop with a 330hp 454. They probably do the tests in saltwater, which I remember last time I took my Chris craft down to the gulf, it felt like someone added a whipple charger on there.

Another thing i thought of. The boat has trim tabs, and they are mounted flush with the bottom. I never use them, should i remove them? Are they slowing me down even when they are in the full up position? On my buddy's boat when his tabs are all the way up, I noticed his tabs are angled a few degrees above the waterline.

one other issue. Today I put a tarp down on the ground and crawled under the boat between the trailer bunks...ran my hand along the hull and discovered a thick layer of calcium/lime deposits. It sat in a wet slip for the last 3 summers. I always pressure wash it when I pull it in the fall, but I guess I'm only getting the green/brown algae slime. Plus on the trailer I can't get it all. Looks like an acid wash from a local marina is in my future.