Something Is Not Right?
04-28-2011, 10:12 AM
#11
VIP Member
VIP MemberJoin Date: Oct 2006
Posts: 210
Likes: 0
Received 0 Likes
on
0 Posts
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.
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.
Last edited by Sport 280; 04-28-2011 at 10:33 AM.
04-28-2011, 10:56 AM
#13
Registered
Join Date: Jan 2009
Location: Wilson, NY
Posts: 935
Likes: 0
Received 0 Likes
on
0 Posts
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). 
Your throttle blade is straight up and down in the carb when your at full throttle right ? (adjustment)
Your throttle blade is straight up and down in the carb when your at full throttle right ? (adjustment)
04-28-2011, 11:23 AM
#14
Charter Member # 55
Charter Member
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.
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.
04-28-2011, 11:27 AM
#15
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 112merlin 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.
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 112merlin 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.
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
04-28-2011, 12:53 PM
#16
VIP Member
VIP MemberJoin Date: Oct 2006
Posts: 210
Likes: 0
Received 0 Likes
on
0 Posts
Now if the cam was installed before top dead center, then engine would likely not run or run very poorly.
Last edited by Sport 280; 04-28-2011 at 01:55 PM.
04-28-2011, 03:04 PM
#18
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.
Now if the cam was installed before top dead center, then engine would likely not run or run very poorly.
. You are correct. 112 seems quite a bit RETARDED for a Boat Motor, pushing the HP range further up the rpm scale.
04-28-2011, 08:13 PM
#19
Registered
Thread Starter
Join Date: Feb 2011
Location: Chatt, TN
Posts: 27
Likes: 0
Received 0 Likes
on
0 Posts
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. 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.
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.
04-29-2011, 06:29 AM
#20
Registered
Join Date: Nov 2001
Location: Pennsylvania
Posts: 3,385
Likes: 0
Received 0 Likes
on
0 Posts
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.
