Something Is Not Right?
 

Ok I have a 93 Sonic 28 ss w/ a single bb. Last week installed new/ rebuilt Gen 6 502. 600 hp
bored 30
srp forged flat tops
moly rings; first ring gaped at 28 thousands, 2nd at 26
merlin heads
teague hyd roller valve train.
cam is 610/ 632 lift 236/ 244 dur @50 112 cl
cloyes adjustable timing gear. cam was degreed in at 112
merlin air gap intake
holley 800
msd distributor (ready to run) msd coil
ngk plugs -9 series
imco powerflow exhaust w/ extensions, no silent choice
bravo 1 w/ 1.50 gears

First sea trial results. 61 mph gps at 4,900 rpm using 26p b1 lab. Prop slip is 24%! moved the timing up and down a little, slight improvement. Fuel pressure was always above 6 psi.

I know the quick fix is trying different props which I'll try out soon. However I believe this motor should be able to turn a lab 26 b1 to the desired 5,800 rpms.

What's wrong with this setup? Is the factory X dimension creating to much drag from the drive sitting so deep? I believe the prop centerline is close to 7" from the bottom of the hull.

What was the previous power/hp and how fast did it run?

Deep drive and 4 blade prop on a non stepped hull is not a good combination. Try a mirage + 25 pitch three blade. But with that much slip the engine should turn more RPMs. If you advanced the cam to much top end will really suffer. Was the cam installed according to the cam card? Was the 600 hp from a dyno? Your combination is very close to a Merc HP500 which makes about 470 hp. Not a lot of power for a heavy single engine boat.

Early sonics are fairly heavy boats. You will likely need a prop you can spin at 5400 RPM to get power from the combination you listed, maybe even a 23.

But what were you running before the new power? Prop, Horsepower, rpm?

You need something to compare to the new setup.

My 28 ss with 502 Mag had a Mirage 23 pitch 3 blade. The drive is probably too deep. I should have some 23, 25, and 27 pitch right hand props. Shoot me a PM and I will check in the barn.

Dang power keesp going out. So let's try posting again.

Previous motor was a clone hp500. tried various props and the overall best one was a lab bravo1. Best speed was 63 mph on gps, 4850 rpm 1-2' chop light load using a lab 26p b1.

New motor has more compression, better valve train, iginition, heads, etc. Cam was degreeded in per specs. It makes more power than the latter.

Thats why it doesnt make sense. Almost exactly the same rpms and speed. It feels like you hit a wall at 4,900 rpm, just stops pulling.

What is your timing set at?
You may have a very deep drive but more power is more power.

540 with -2 imco shortie

Great response. Thanks for your insight on this matter.

Timing is 35 degrees overall.

:lolhit: I love the sarcasm. And what?? A whole new setup isnt in your budget this year???

Starting a little lower in pitch would be a good start. Know any buddies that can lend you something to try? Or perhaps a local place for trial and error. A lot of guys reccomend BBlades. I may be giving him a call too! Best of luck to you. :coolcowboy:

What are the dyno numbers ? Did it go 5800 on the dyno ? That is the place to tuneup the engine.

More power is more power, but it takes 18 to 20 additional horses for each 1 mph increase. What were dyno and torque numbers. With big heads and cam, you will have to turn higher rpm to get to power, but with heavy single engine boat will need to drop down in prop pitch. If you were close to 500 horse with other engine and running a 23 at less than 5000 rpm, you were not getting into the horsepower range of that engine.
If you assume new engine is making an additional 100 horses, may get another 5 mph. But you will need to drop in pitch to get the engine to turn enough rpm to reach that additional horsepower(likely new engine set up has moved hp and torque up the rpm scale).
Bottom line, you need to know HP/Torque curve to determine where power is and then prop to get into the power band.

Not that it is stopping you, but the #9 plug is too cold. You should be around #6.

What is the jetting in the carb? What is the compression?

Personally...I think the 800 carb is a little too small for the combination you have. Secondly...it sounds to me like your not getting enough fuel volume. You have pressure, but not enough volume. I suggest running a larger fuel line directly from the pump to the carb sir (oh, and make sure you got enough pump). :drink:

Your throttle blade is straight up and down in the carb when your at full throttle right ? (adjustment)

What is the compression ratio????

I don't see that combo making 600hp, unless there is something that is not listed. More like 550hp.

The drive seems way low. I would try a -2 shorty lower.

112 ICL :eek: are you sure that's not the Lobe separation your talking about? That's a long way's to advance a boat cam. Most are about 106

Actually, 112 is not advanced. Most cams are installed from about 105 to 112 degrees after top dead center. 105 is considered advanced and 112 is considered retarded. About 109 is generally what is used in boat engines.

Now if the cam was installed before top dead center, then engine would likely not run or run very poorly.

I'm sure he meant 112 LSA. And sport is right, a lower ICL is advanced, higher is retarding the cam.

My bad :lolhit:. You are correct. 112 seems quite a bit RETARDED for a Boat Motor, pushing the HP range further up the rpm scale.

Yes 112 Is the LSA which is also what the cam was degreed in at. I retarder the cam too much so I guess that makes me retarded. :lolhit: No wonder why I can't spin that prop. Dang this SUCKS!

Also this motor was not dynoed. Yes it should've been but I simply ran out of time. The machine shop put me months behind schedule. Summer was fast approaching, poker run, work load, etc. Anyways thats engouh excuses for now. Chalk this up to another lesson learned.

The bigger issue with the ICL set at 112 is reversion. The exh valve is open for more piston downstroke degrees which can be trouble in wet exhaust apps. If that is not an issue I would attempt to prop it for the current hp max rpm, see what you get.

What does the cam card say the INTAKE CENTERLINE should be? If you infact set the intake centerline (max. lift) at 112, that is not correct. The LSA is Lobe Separation Angle, it is determined from the intake and exhaust centerline numbers.

I think that he has the crane 741 cam which should be a recommended 107 ICL.

At least you know now. Should make a measurable difference in the way the motor runs.

Don't feel bad. My Machine shop had my block for 3 frickin months.. for about 3 days worth of work :angry-smiley-038:

Its the same grind as a crane 741. I won't name names but the supplier did not include the cam card. I should have verified it regardless. A 5 minute phone call would've prevented this. The ICL should be 107, I'm at 112, 5 degrees of retardation. Now I get to pull the motor and spend 2 days correcting this phuck up.
Fun Fun

Why pull the engine???? You should be able to pull the timing cover off and degreee it in properly in the boat.

Update
 

The oil pan has to drop down in order to pull the timing chain cover. I dont think its possible to degree a cam with the motor in the boat. Maybe if you had a two piece timing chain cover.

I pulled the motor on Sunday and took off all necessary parts. Degreed the cam to 107 ICL. Glad I reset the ICL because I found signs of water reversion. Milky oil residue under the valve covers, top of heads. Next everything was put back together. The motor will be installed by weeks end. Will post update after sea trial.

Update
 

Man its one thing after another. The motor is back in the boat with the cam degreed in at 107 ICL. Started the engine an ran it for a short time. Found water pouring out the bottom of the oil cooler next to the power steering nipple. Water is mixing with both the oil and power steering fluids.

New cooler and fresh oil should be here before the weekend. This build is down to the wire. Our poker run is only a week and a half away.

bingo i would have put that cam in at 108 for that heavy of a boat

ok i did not read all three pages before i posted. After you get the cam in right you might play with a larger carb i have had good results with close to 1000cfm on similar combos although most will say it is to much carb. I have 2 496's in a 32 active thunder that i have 1050 dominators on , the motors made 640 at 5600 with the big carbs.

Cam was reset to 107 ICL. Engine was reinstalled. Ran engine and found water in oil. Installed new oil cooler, cured problemn.

Sea trail resulted in 66 mph gps @ 5,400 rpms with new 22 B1. It pulls hard all the way thru the rpm range. All in all its running pretty good.

Still have some minor tunning and misc parts to change out like coil and warmer plugs. I think there's another 1-3 mph waiting to be unleashed. We'll find out.

Glad to hear its running better. Just keep an eye out for reversion, with a 112 LSA you are on the borderline.

I would check around with others running the same exhaust as you are and hot cams to see if they had any problems

Excellent! Now go have fun. :drink:

Great news. Glad to hear it :drink: