489 with only 14 hrs compression #s
 

#1 170 psi
#2 160 psi
#3 175 psi
#4 165 psi
#5 155 psi
#6 155 psi
#7 160 psi
#8 160 psi

Cold engine, throttle wide open.

Boat runs strong, but disappointed with top end of only 50mph @500rpm, 20 pitch Turbo 3 blade. 89 Chap 2550sx. May try a 23p mirage i have lying in my garage. Do these #s indicate a motor that is in the process of being broken in, therefore more power is on the way, or something amiss!

what rpm?

sorry meant to say 50mph @5000rpm.

What kind of rings did you use? Also assuming you have a fresh grind on valves and seats? Was it bored or honed? Heads and blocked surfaced? 14 hrs is plenty of break in time. Mine typically take less then 14 minutes. Doubt you'll see any more gains. I would do a leak down on a couple of your lower 5 and 6 and see where its going? 100% on, would be nice but not always realistic. Your within or close to being within 10 % but so do several engines with over a three or four hundred hard hours on them. I've seen cylinder rings seat quicker than others on the same engine however with that kind of time you should be set. Have you built multiple good heat runs in it during the 14hrs and let cool good btwn? If you don't have a leak down tester go rent or borrow a good one. At the very least it may ease your mind a bit. Give us a little more info your recent build and who did it etc?

I would definately start the process of elimination. That is enough to be a little concerned.

not sure on the rings, my engine builder picked them. Engine was bored 30 over, heads and block surfaced, all new valvetrain. To be honest I really have only had it over 4500rpm 2 times: once last summer, and then 2 days ago. I guess I need to get on it some more

Well that hull is not very fast); 45 with a stock 330. It's very heavy. Not trying to knock the boat I had one but they were built like cruisers. I would try that 3 blade. Your motor numbers look fine.

I know, its not a performance hull, its a deep vee and very heavy. It's just I really spent a lot of money on the engine, stroker crank, 500hp heads,cam from Bob Madera, roller setup, and to only pick up 2-3 on the top end seems like I wasted a lot of money, could have just done a stock 454 mag rebuild or something for probably half of what I spent. Will see what the 23p does and then go from there. Maybe a 4 blade with more lift would help.

What carb, intake, and exhaust are you running? Was any work done on the heads in the valve bowls or combustion chambers? A lot of the 2550's came with thru-prop exhaust - are you running yours out the transom?

What is your initial and total timing set at?

Little things like incorrect timing and jetting in the carb can make a huge difference on the power output of an engine.

BTW, I almost bought a 2550 years ago that had a stock 330 in it. When I test drove it, I got it up to an easy speedo-indicated 55 mph without even playing with the trim for best top end. Of course, that was speedo-indicated and not GPS, but if 50 is all you are getting with a warmed over 489, something is wrong.

Running exhaust out the transom. Using a demon 850 with edel air gap. I have my initial timing set at 8 deg, not sure of total.

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.

The "shag carpet" can cause significant drag, but I would not think more than a few MPH worth. Besides, it still does not explain why you are seeing virtually the same speeds as your old 330.

Used to own a 91 with a 365 hp 454 with silent choice that would run over 52 and had over 750 hours on it . 23 pitch prop is what I ran . The biggest problem with these boats is air or should I say a lack of , to the engine . I could get 2 mph on the GPS just by lifting the hatch a few inch's while I was running . I'm sure you would need more air than my stocker did . Might be worth a try after you get the bottom clean. :drink:

Well actually with the old motor the bottom was clean, slick for the 1st season. Previous owner kept it trailered. I could hit 48 gps. Then it sat in the water all summer 08 and winter of 2008/09. spring 09 it felt slower, could only hit about 42 mph. That combined with low oil psi, I assumed a rebuild was around the corner, so I took it slow all summer 09, added some lucas oil, and just cruised around, never went above 3000 rpm. Pulled boat out motor in fall, rebuild, 489 roller motor. Put back in water Spring 2010, bought jet skis for my kids, only put 14 hrs on new motor. Pulled boat out last fall, pressure washed scum off. I need to get the crap off of it anyway, so its getting an acid wash this week. What about the trim tabs?? Should I get rid of them.

update!! Had the bottom acid washed and buffed...56 mph on the top end @ 5200 rpm!!! The white chalky lime deposits were really slowing the thing down. This is with the 20p 3 blade turbo prop. Still need to try the 23p mirage. might try a 4blade 21p as well.