once you get the right setup on yours you will find you can let it run
this one has a volvo speedmaster E drive on it and a warmed up Ford SB windsor
When the sky is grey,look out to sea.
When the waves are high and the light is dying,
well raise a glass and think of me...
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no head on the 16 that's my new old boat the hornet that has the head
a good prop solves a lot it will stop porpoising or limit the speed ranges that it occurs will carry the boat at a level angle of attack not to much stern lift or bow lift not sure what the merc guys are running on the 16 Rootsy had his merc alpha ss drive setup running mid 70s you will know when you have the right prop the boat will become predictable
the 16 actually benefits from a little more wetted surface over the 18 or 22 makes the ride more stable
When the sky is grey,look out to sea.
When the waves are high and the light is dying,
well raise a glass and think of me...
When I'm home again,
boys, I'll be buying!
My Ride
Come Join Us on The Queen Of American Lakes
Contact Us
www.lgdonziclassic.com
When the sky is grey,look out to sea.
When the waves are high and the light is dying,
well raise a glass and think of me...
When I'm home again,
boys, I'll be buying!
My Ride
Come Join Us on The Queen Of American Lakes
Contact Us
www.lgdonziclassic.com
the 16 will take alot more punishment than the passengers can handle that's why I am not in one anymore
a skilled passenger will assume the position facing fwd both hands on the front of the rail one leg knelt on the passenger bench seat the other foot on the floor
When the sky is grey,look out to sea.
When the waves are high and the light is dying,
well raise a glass and think of me...
When I'm home again,
boys, I'll be buying!
My Ride
Come Join Us on The Queen Of American Lakes
Contact Us
www.lgdonziclassic.com
Regarding your prop, we need: engine, drive ratio, what make and pitch prop you now have, GPS MPH, and rpm you get and what you want.
More than other advice: SEAT TIME.
John C[/QUOTE
OK John here is what I'm running...
- Mercruiser 5.7 estimated to have 400HP
- Owners manual says the outdrive ratio is a 2.0
- WOT was 49 MPH at 4,100 RPM
- Current prop is a Ballistic 14 & 3/8 x 21
- Spare prop is an Apollo HXS 14 & 1/8 x 19, the original owner replaced it because the RPM's were going to high.
I just want to find the most appropriate prop to make it as user friendly as possible for now. I can experiment with others as I get to know the boat better. That's my initial thought but I'm happy to listen to anyone else's experiences and can be persuaded
ratio is 1.5 ... unless wrong drive on the boat and it still wouldnt be 2.0... no such thing
Is the 5.7 " built " ? ... where did the 400 hp come from ?
Last edited by Lenny; 08-01-2017 at 11:56 PM.
I have to agree with Lenny's comment re drive ratio, I run a 1.81 and can swing a 23" Lazer at 4800 on a V6 with half your claimed horse power !!
lenny is right on your setup if that 21 prop is at 10% slip is a 1.5 ratio
something is not right I am not a chevy or a merc guy but I would think a sbc would be fine spinning 4500 on a daily basis try the 19 and see what ya get so you have numbers to compare
running a 19 at 4500 with 10% slip should be around the same speed
again these numbers surprise me they are what an older volvo numbers look like the merc with trim and better hydrodynamics should be north of 50 easy
John C just repowered he has a modern lower unit he would be a good benchmark
as a comparision my 16 with 310hp a volvo 250 with a nose cone and 1.6 ratio ran around upto 60 at 5000 with no trim and no hydrodynamics
sounds like time you go thru everything
When the sky is grey,look out to sea.
When the waves are high and the light is dying,
well raise a glass and think of me...
When I'm home again,
boys, I'll be buying!
My Ride
Come Join Us on The Queen Of American Lakes
Contact Us
www.lgdonziclassic.com
I have a lot to learn guys....
I am going to have to look into the outdrive ratio further to be certain, I questioned it after posting and learned very quickly that it should not be the correct ratio for a V8 boat.
The 5.7 is bored .30 and the person who built it estimated it to be at or close to 400HP. He built motors for hydroplane racing and said that he had built several and had enough experience to give an accurate estimate.
This is current as of 11/17/2016 ***ENGINE***
- Trick Flow Aluminum Cylinder Heads
- (Assembled With 2.02 and 1.60 Valves, New Springs, Retainers, Keepers, and Seals)
- Scat Crankshaft Standard Weight Forged 4340 Steel Internal Balance
- Scat Connecting Rods 4340
- IBeam Sealed Power Hypereutectic Pistons and Rings
- Chevrolet Performance 350 Magnum Marine Hydraulic Roller Tappet Camshaft
- Comp Cams Magnum Steel Roller Tip Rocker Arms
- Comp Cams Magnum Pushrods
- Comp Cams High Energy Hydraulic Roller Lifters
- Comp Cams Magnum Double Roller Timing Chain and Gear Set
- Professional Products Steel Harmonic Balancer And Pointer
- Chevrolet Performance Flex Plate
- Chevrolet Performance High Volume Oil Pump
- Weiand Action Plus High Volume Aluminum Water Pump
- ARP High Performance Series 8740 Chromoly Steel Bolts Used Throughout
- FelPro Gasket Kit
- Edelbrock Performer Intake Manifold
- Edelbrock Marine Carburetor (Installed)
- QuadraJet Marine Carburetor (Spare)
- K&N Flame Arrestor
- New Custom San Juan Engineering Fresh Water Cooling System
- EMI Thunder Polished Aluminum Exhaust System (AntiFreeze Cooled Manifolds)
- New Fuel Pump
- Braided Stainless Steel Fuel Lines
- New Ignition Components With NGK Iridium Spark Plugs
- Remote Oil Pump Out
Thank you for the time & help btw
21" pitch at 4100 with NO slip would indicate about 54 mph WOT with a 1.5. But, you are missing a thousand rpm, 4100 is like a high cruise. At 5000 rpm you would see 66 with NO slip.
Something is amiss.
When the sky is grey,look out to sea.
When the waves are high and the light is dying,
well raise a glass and think of me...
When I'm home again,
boys, I'll be buying!
My Ride
Come Join Us on The Queen Of American Lakes
Contact Us
www.lgdonziclassic.com
It looks like we're starting to get to the facts. Are you sure your tach is reading correctly? (During my Repowering the shop found mine was good up to a certain rpm, then went 1000 rpm low). Are you using gps for speed? I don't have a Merc drive but the reduction ratio may be stamped or noted on a tag.
Using your numbers, prop slip is an impossible -20%. At a 1.5 ratio, slip is a reasonable 10%. Is the engine unable to turn faster than 4100 rpm? Sound starved? Hiccups? Something is wrong with the numbers. You should get minimum high 50's with 400 hp and a 21" prop.
My oem 5.0 HO best ever, cool day, alone and half tank of fuel, was 59.8 GPS @ 4,850 rpm using a tweaked SST 21" prop. Best info I could find says I had 200 HP from that engine.
John C
'92 Sweet 16 302 FordWindshields are for Sissies!!!
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