SBC Black Scorpion Improvements.

[squeezer]

2009 Sanger V215 46MPH @ 4800RPM
2008 5.7 Black Scorpion (PCM555 EFI computer)
Freshwater only

Looking for a few more horsepower and a bit more RPM for the odd barefoot run. Would not mind taking a few pounds off the stern as well.

Currents thoughts are as follows:

Start with exhaust. ($1-3K)

CMI's or a higher quality cast aluminum set.

(Are CMI's going to show much improvement on a 375ish horsepower SBC?)

Then heads. ($1.5K)

Aluminum of some sort.

Edelbrock E Streets, Fast Burn Bowties, AFR, ?????


Finally a re-flash: ($0.5K)

https://whipplesuperchargers.com/index.php?dispatch=categories.view&category_id=177

(It looks like Whipple is the only game in town for the PCM555 based system.)


The above combination at $4500 should be good for close to 375HP and remove just about 200 lbs off the stern.

Do any of you guys have a specific combination that can be recommended?

 

[Trash]

2009 Sanger V215 46MPH @ 4800RPM
2008 5.7 Black Scorpion (PCM555 EFI computer)
Freshwater only

Looking for a few more horsepower and a bit more RPM for the odd barefoot run. Would not mind taking a few pounds off the stern as well.

Currents thoughts are as follows:

Start with exhaust. ($1-3K)

CMI's or a higher quality cast aluminum set.

(Are CMI's going to show much improvement on a 375ish horsepower SBC?)

Then heads. ($1.5K)

Aluminum of some sort.

Edelbrock E Streets, Fast Burn Bowties, AFR, ?????


Finally a re-flash: ($0.5K)

https://whipplesuperchargers.com/index.php?dispatch=categories.view&category_id=177

(It looks like Whipple is the only game in town for the PCM555 based system.)


The above combination at $4500 should be good for close to 375HP and remove just about 200 lbs off the stern.

Do any of you guys have a specific combination that can be recommended?

First off serial number off the motor will help positively ID the configuration. Is it really the 5.7 or the 377/6.2 motor?

Don't wast your money on exhaust. You will see virtually zero measurable gain (in the boat). Stock exhaust is not a limiting factor on SBC marine motors as long as its through transom and NOT through the prop. Performance increase due to lighter exhaust will not be measurable.

You could change heads but with the stock cam you would then be cam limited. With stock internals you'd want to keep the rpm reasonable. My personal limit with cast internals and hypereutectic pistons would be 5000ish rpm. It is likely you have the GM "395" cam in that motor. It falls on its face at 4800 rpm. Changing heads won't likely yield much of an improvement especially since you have Vortec heads already.

Watch combustion chamber size as you could likely increase or decrease the compression significantly.

What intake do you have? The tunnel ram style? Single or dual stage throttle bodies?

Any major mods would be best suited with a modified tune. Being a PCM 555 motor severely limits who can do this.

IF you wanted to bump the power a little I'd clean up the existing heads (assuming they are Vortec), put a (reasonable) cam in it, thru hull 4" exhaust, good valve train coupled with a tune and call it a day. Beyond that you need to pull the motor and beef up the bottom end and stroke it if able.

Best of luck.

 

[squeezer]

First off serial number off the motor will help positively ID the configuration. Is it really the 5.7 or the 377/6.2 motor?

I am sure its the 5.7...

Don't wast your money on exhaust. You will see virtually zero measurable gain (in the boat). Stock exhaust is not a limiting factor on SBC marine motors as long as its through transom and NOT through the prop. Performance increase due to lighter exhaust will not be measurable.

Raw performance numbers probably don't justify the expense but damI like the look of CMI's and as important this is a fairly light hull that skis much better with two people in the boat than three. (I literally pull the anchor, my tool bag, spare prop, etc out of the boat when we go out for a morning ski only type session.) You can feel the difference behind the boat.

You could change heads but with the stock cam you would then be cam limited. With stock internals you'd want to keep the rpm reasonable. My personal limit with cast internals and hypereutectic pistons would be 5000ish rpm. It is likely you have the GM "395" cam in that motor. It falls on its face at 4800 rpm. Changing heads won't likely yield much of an improvement especially since you have Vortec heads already.

Watch combustion chamber size as you could likely increase or decrease the compression significantly.

Have been assuming that aluminum heads would let me run a bit more compression, would likely go with 1.6 rockers to help the stock cam out a bit. I really don't want to pull the engine so a cam change is off the table at the moment. I would likely build a stroker motor on the bench and sell this one outright if it came out... Prop would be pitched to keep the RPM at 5100 or so at WOT


What intake do you have? The tunnel ram style? Single or dual stage throttle bodies?

Tunnel ram style with 90mm throttle body... have no idea if its single or dual stage.

Any major mods would be best suited with a modified tune. Being a PCM 555 motor severely limits who can do this.

Is Whipple the only game in town for a tune?

IF you wanted to bump the power a little I'd clean up the existing heads (assuming they are Vortec), put a (reasonable) cam in it, thru hull 4" exhaust, good valve train coupled with a tune and call it a day. Beyond that you need to pull the motor and beef up the bottom end and stroke it if able.

See above on a cam change...

Best of luck.

Comments/questions above...

 

[Trash]

Raw performance numbers probably don't justify the expense but damI like the look of CMI's and as important this is a fairly light hull that skis much better with two people in the boat than three. (I literally pull the anchor, my tool bag, spare prop, etc out of the boat when we go out for a morning ski only type session.) You can feel the difference behind the boat.

Understood. But you will be north of $2500 JUST for a set of stainless steel tubes. IF you want to reduce weight get a set of aluminum GLM stock style manifolds. GLMs or stock manifolds will flow well above 5000 rpm so they aren't a limiting factor.

Have been assuming that aluminum heads would let me run a bit more compression, would likely go with 1.6 rockers to help the stock cam out a bit. I really don't want to pull the engine so a cam change is off the table at the moment. I would likely build a stroker motor on the bench and sell this one outright if it came out... Prop would be pitched to keep the RPM at 5100 or so at WOT

The 1/2 point of compression you might be able to get won't be noticeable in my estimation. The duration of the cam is your choke point if it is the '395' cam (the 395 is the last three numbers of the cam part #) You'll be wasting a lot of money on heads that will flow more than what the cam can offer. The Vortecs are plenty for what you are gunning for.

Tunnel ram style with 90mm throttle body... have no idea if its single or dual stage.

I believe you have a single stage TB if its the 90mm blade.

Is Whipple the only game in town for a tune?

I think he and a few others but don't ask me to name them because I don't know them all. Mark Bose (sp?) in Louisiana might do it as well.

What prop and drive are you spinning right now? What drive ratio?

Is your 46 mph at 4800 rpm WOT? The reason I ask is that if your current motor makes 375ish HP something doesn't add up. You should be going a lot faster with that kind of HP. Now I know it sounds like I'm trying to rain on your parade, but I'm not. I want you to succeed, I really do.

Are you simply looking for 300 rpm? Aluminum GLM manifolds (weight reduction if so inclined) and perhaps some prop work (rpm increase) would be your best bet. IF you indeed have the cam I think you do (which is a great cam for certain segments) then I'm suspect it will pull more than 5000 rpm.

Any substantial performance increase to be obtained using your existing motor would require the full spectrum of complimentary enhancements. Stroker crank, pistons, cam, lifters, springs, heads, materials, injectors and tune. As much as I'd like to say just add heads and your good I don't believe it would be effective. I might be wrong, but you'd be into a lot of money with very little improvement.

Best of luck

 

[squeezer]

Understood. But you will be north of $2500 JUST for a set of stainless steel tubes. IF you want to reduce weight get a set of aluminum GLM stock style manifolds. GLMs or stock manifolds will flow well above 5000 rpm so they aren't a limiting factor.

The 1/2 point of compression you might be able to get won't be noticeable in my estimation. The duration of the cam is your choke point if it is the '395' cam (the 395 is the last three numbers of the cam part #) You'll be wasting a lot of money on heads that will flow more than what the cam can offer. The Vortecs are plenty for what you are gunning for.

I believe you have a single stage TB if its the 90mm blade.

I think he and a few others but don't ask me to name them because I don't know them all. Mark Bose (sp?) in Louisiana might do it as well.

What prop and drive are you spinning right now? What drive ratio?

Is your 46 mph at 4800 rpm WOT? The reason I ask is that if your current motor makes 375ish HP something doesn't add up. You should be going a lot faster with that kind of HP. Now I know it sounds like I'm trying to rain on your parade, but I'm not. I want you to succeed, I really do.

Are you simply looking for 300 rpm? Aluminum GLM manifolds (weight reduction if so inclined) and perhaps some prop work (rpm increase) would be your best bet. IF you indeed have the cam I think you do (which is a great cam for certain segments) then I'm suspect it will pull more than 5000 rpm.

Any substantial performance increase to be obtained using your existing motor would require the full spectrum of complimentary enhancements. Stroker crank, pistons, cam, lifters, springs, heads, materials, injectors and tune. As much as I'd like to say just add heads and your good I don't believe it would be effective. I might be wrong, but you'd be into a lot of money with very little improvement.

Best of luck

A bit more info may be useful.

The boat is a 21 foot tournament style V-drive. Not a huge wakeboard/surf hull by current standards but still having the speed limitations inherent to the layout. Horsepower is the stock 330, and I believe that is at the crank not the prop.... The 375 number thrown out above is what I expect the mods to get the engine close to. (This is a guess based on the 377 scorpion, which would not have as good a head or exhaust as I am considering running.)

 

[Trash]

Makes sense now. That mph and the 330 hp motor makes sense. Have a friend with a MasterCraft LTR 330 hp motor (similar to the Scorpion) and it runs the same. The Scorpion 377 made the extra hp via the stroker crank (cubic inches) and perhaps some minor camshaft improvements. Not sure if the heads were different.

I was hoping others would chime in for options I may not be seeing. In the end the hull will be the limited factor for high speed. Since you're only looking for 300 rpm or so I'd still wager that perhaps lighter exhaust and some prop blue printing (labbing) 'may' do the trick. At least that would be your cheapest and least invasive option.

Just go big and shoe horn a 572 tall deck in there!

Best of luck.

 

[AzGeo]

You need to rebalance the boat, so that it runs with the nose UP and the tail down. V-drive style boats can be rebalanced at a "3" to 1" ratio. Moving the prop 1" is like moving the motor and trans 3", while trying to rebalance the boat for higher top speeds. You guys are looking at MOTOR POWER and I am looking at HULL DRAG. If the motor, trans and V-drive run well, DON"T FIX THEM. What prop do you have and what is it's best GPS performance ? I'm telling you to MOVE THE PROP FORWARD (this lifts the nose) and allows more top speeds per RPM, if the prop is not a POS. Real V-drive guys build a boat that runs 'hog wild' and then adds plates to make it controllable. Your prop is "so far back under the boat", that it wants to BURRY THE NOSE at all top speeds. I have not seen pix of this boat running, but I'll bet that moving the prop forward 1" will make a major difference in how this boat performs. Moving the prop forward more, is like moving the center pivot of a sea saw, and the boat reacts in a similar manner. I've tried to tell others in the past, "you can double the motor power and only add 15 MPH to a boat you cannot control", so why go that direction ? You can throw money at the motor, but it will never cure the problem you have, go with "re-trimming" the package to be the same boat you liked, just at a faster speed ?

 

[Trash]

You need to rebalance the boat, so that it runs with the nose UP and the tail down. V-drive style boats can be rebalanced at a "3" to 1" ratio. Moving the prop 1" is like moving the motor and trans 3", while trying to rebalance the boat for higher top speeds. You guys are looking at MOTOR POWER and I am looking at HULL DRAG. If the motor, trans and V-drive run well, DON"T FIX THEM. What prop do you have and what is it's best GPS performance ? I'm telling you to MOVE THE PROP FORWARD (this lifts the nose) and allows more top speeds per RPM, if the prop is not a POS. Real V-drive guys build a boat that runs 'hog wild' and then adds plates to make it controllable. Your prop is "so far back under the boat", that it wants to BURRY THE NOSE at all top speeds. I have not seen pix of this boat running, but I'll bet that moving the prop forward 1" will make a major difference in how this boat performs. Moving the prop forward more, is like moving the center pivot of a sea saw, and the boat reacts in a similar manner. I've tried to tell others in the past, "you can double the motor power and only add 15 MPH to a boat you cannot control", so why go that direction ? You can throw money at the motor, but it will never cure the problem you have, go with "re-trimming" the package to be the same boat you liked, just at a faster speed ?

Not being intimately familiar with inboard set ups this is likely a better route to go. Great info.

 

[squeezer]

The prop is a 13X12 3 Acme 3 blade. There is about an inch and a half of room between the prop and the strut. Not sure how a person would go about moving the prop ahead other than shortening the propshaft at the coupler end. As far as attitude tuning options. The hull has an adjustable wake plate that is about 20 inches wide and 15 inches deep. Mounted "Cavitation" plate style with turnbuckle adjustment. I mention that because there is enough "trim" sensitivity with just a few turns on the plate to notice the difference. If it is trimmed up a little much the hull will porpoise a bit around 28MPH but you get through it fairly quickly. (Adding an electric cave plate adjuster and associated hardware is intriguing.).

There all all kinds of prop geometries for stern drives (Bow lifting, stern lifting as an example likely tuned through blade rake...) I have not seen the same options for tournament type V/Direct drives. Truth be told it would be hard to say which direction to go without some testing. Some stern lift and less plate would probably ski better than a bow lifting prop for instance. (Not sure how that would impact top end however...???) Which is inline with wanting to take some cast iron off the stern.


But looping back around I am just hoping to get some input from somebody who has modified the Mercury 5.7 Black Scorpion.

 

[Trash]

But looping back around I am just hoping to get some input from somebody who has modified the Mercury 5.7 Black Scorpion.

I have modified the earlier sister of that motor.