Building a performance 5.7 Engine, What parts are needed?

I have a 2001 Mercruiser Vortec 5.7 250HP carbed with 2 brl. carb. I have a 20' Ft Regal boat that weighs about 2800 lbs with the engine. I am using the alpha 1 gen 2 drive.

What HP can I safely make with the alpha and this weight of boat? Given that the boat is relatively light, can I run say 330 prop HP or more? This is of course assuming I do not frequently do full power hole shots.

Does it benefit the Alpha to do through-the-hull exhuast? Does it keep it cooler?

Lastly, what parts would I need to by to reach a good power level? Is a high rise intake manifold a good choice? Any recommendations on which one? What carb is the best choice? What about cam shafts and roller rockers? Are the Vortech heads my best option?

Thanks in advance!

Re: Building a performance 5.7 Engine, What parts are needed?

Save your money and engine and leave it alone. When you start changing the cam duration you will experience water intrusion back into the cylinders. Building an engine like you would a hot rod doesn't work well in a boat. At least not for long.

Re: Building a performance 5.7 Engine, What parts are needed?

I'm with Capt Ken about leaving your boat as it is. You could plow a bunch of big $ into the boat, however you've got to realize there are limitations with your hull. You can get marginal performance increases, but the investment might not be worth the effort.

If you're wanting a high performance boat, start with a good used Sea Ray Pachanga or other high performance hull.

Re: Building a performance 5.7 Engine, What parts are needed?

Others may want to correct me, but here's a good rule of thumb to calculate the cost of performance.

If you are already starting out with a boat that is powered correctly from the factory, you will need to spend $1,000 for every 1 mph increase in speed you will see on the water. This is assuming you are using new marine service parts, and are paying a pro to install them. Boat performance costs WAY more than car or motorcycle.

Good luck!

Re: Building a performance 5.7 Engine, What parts are needed?

Going to a better intake and carb is a good place to start. Since you have the 2b.

There are lots of options for cams.
First and foremost you haft to think about the negative pulse in the exhaust caused buy to much valve overlap will suck water up and destroy the eng.

Going to a marine roller cam can free up some hp as long as your heads and intake are up to the task.
Going overboard on the intake and carb will not do you much good as the exhaust if pretty restrictive in stock form. So don't over do it or you will end up with a dog out of the hole that drinks gas.

Re: Building a performance 5.7 Engine, What parts are needed?

jserr68594 said:

I have a 2001 Mercruiser Vortec 5.7 250HP carbed with 2 brl. carb. I have a 20' Ft Regal boat that weighs about 2800 lbs with the engine. I am using the alpha 1 gen 2 drive.

What HP can I safely make with the alpha and this weight of boat? Given that the boat is relatively light, can I run say 330 prop HP or more? This is of course assuming I do not frequently do full power hole shots.

Does it benefit the Alpha to do through-the-hull exhuast? Does it keep it cooler?

Lastly, what parts would I need to by to reach a good power level? Is a high rise intake manifold a good choice? Any recommendations on which one? What carb is the best choice? What about cam shafts and roller rockers? Are the Vortech heads my best option?

Thanks in advance!

Click to expand...

Ayuh,.... The Alpha drives are limited to 300 hp, regardless the hull it's in....

Thru-hulls create Noise, not hp...

Ya, a hi-rise manifold, 'n Edlebrock carb is a Good move...

Yer motor already has Vortec heads, 'n a decent cam now...

Re: Building a performance 5.7 Engine, What parts are needed?

the cam can be increased up to 268 - 270 degrees of duration prior to reversion. you already have vortec heads and a roller cam.

you can put more power thru the alpha, however you can NOT give it full on the hole shot. I know people with 383's and 406's in front of alphas. however you have to ease into the power and gradually take off. one good holeshot and you can snap the alpha.

a 268 degree cam, with a decent intake and carb and your pushing about 330hp.

thru-hulls will be louder, however unless you upgrade the exhaust manifolds to something that breaths, you wont notice anything other than the noise.

now, here is the reality.

your going to spend about 2 boat units just updating the cam, intake, and carb. Best price for a packaged mercruiser intake/carb/linkage/etc setup to convert from the mercruiser 2 barrel is about $850. a good vortec roller cam kit with lifters about $800. gaskets, miscellaneous items, new steel fuel lines, etc. about $300. Beer about $100

and you still have not got a new prop or touched the exhaust if you wanted to.

that is $33 per horsepower.

Re: Building a performance 5.7 Engine, What parts are needed?

COMP Cams Xtreme Marine Camshafts - Marine Camshaft Usage - CBVI XM270HR-12 Grind Number - SummitRacing.com 300

Chevrolet Performance Valve Springs 12499224 - SummitRacing.com 70

COMP Cams Steel Valve Spring Retainers 774-12 - SummitRacing.com 40

Edelbrock Performer RPM Air-Gap Intake Manifolds 7516 - SummitRacing.com 260

Edelbrock Marine Carburetors 1410 - SummitRacing.com 400

Gaskets and beer 200.....1200

Valve Spring Upgrade - Beehive Valvesprings for the Vortec V8 - Car Craft Magazine


You have a roller block now i believe that 2000 has apr studs in now if not add 100. There are small gain's by going to a open exhaust that's subjective... About a 5 mph gain overall...but it will feel like a two stroke from 2500 to 5000

Here's the catch putting a new cam and induction system in a tired old 5.7 is not good...but that's a opinion

Re: Building a performance 5.7 Engine, What parts are needed?

I'm pretty sure you'd be borderline with respect to reversion with that comp grind above in a 350 with stock exhaust... it's a little milder / less of an issue with a 383 or 400. I wouldn't go any higher on duration than the next step down without modifying the exhaust. The consequences of getting too close to that line are catastrophic and it's not an exact science. (water in the engine is not a good thing!)

In a more general sense, what are you trying to accomplish? You can build up to a LOT more horsepower, but engine / upgrade cost goes up quickly and reliability goes down as you put more power into your drive. you can also build a performance marine engine to be virtually bullet-proof, BUT it's not the same animal as building a hot rod engine for a street car - you have to build the bottom end a lot stronger and run clearances slightly looser, in addition to choosing components like camshaft differently. I know people that put a LOT more than 300 horsepower in front of alpha drives (one who is probably over 600 in a small light boat). Those drives are efficient and fast, but they become a fairly expensive wear / expendable item as well as a pain in the butt before too long if you overload them too much... I'm only around 450 horsepower and in a significantly lighter boat, but I've for several mangled gear-sets to show for my learning experiences. although it really isn't in my nature to be easy on things... ;-)

I would say if you want a little more pep out of the hole, or even a little more top end, you'll make a noticeable difference with just an aluminum inatke (ie airgap rpm if you have the space, performer if you don't), a 4-bbl carb (edelbrock 1409 is probably easiest and best value), but you could probably do even more and spend less money by lightening the load as best you can and working with props. for example, going from a non-vented prop to the right vented one can increase top end and holeshot both, combined with trim tabs you can wind uip with a large performance increase - depending on where you are already on those things. Major gains in performance beyond what you can get for those kinds of modifications and you would probably be happier in the long run and have more money left in your pocket if you sell your boat for what you can get and buy something faster with more drive and engine already in it. used boats are a bargain these days...

Just some things to think about... Hope this is helpful..

ps. through hull won't cool the engine down or increase performance any at all without a carb, intake, cam and performance exhaust (even then it is not going to make a lot of difference), but it CAN easily make the drive run a little cooler under heavy loads...

Re: Building a performance 5.7 Engine, What parts are needed?

I would question any old aluminum intake as we do not know the location of the OP. fresh water, and the edelbrock is fine. however in salt water, you will need a dual alloy casting, or throw on an HX.

5.0L and 5.7L four barrel hi-rise Vortec intake manifold (96-08)

Re: Building a performance 5.7 Engine, What parts are needed?

Opps bad post upon futher review..Lots of difference between a v8 intake and a v6

Re: Building a performance 5.7 Engine, What parts are needed?

Thank you guys so much for your input. This has given some ideas about how to go about what I am doing. I didn't specify this in the earlier post, but I am using this 5.7L engine to upgrade the current 4.3 in my boat. I will be going from 180 HP to hopefully 300-325 HP. The boat does about 50 now with a 23P prop. I am hoping to make it to the low 60's with this engine.

This is my plan at this point:

-Rebuild the shortblock -To stock specs
-Add a high rise intake -Which one is best for my application?
-Go with a Edelbrock 1409 Carb.
-Possibly a aftermarket cam (Leaning towards sticking with the stock though)
-Swap the outdrive for a 1.47 ratio

Anything else I should do?

Re: Building a performance 5.7 Engine, What parts are needed?

I'd stick with the current drive gear ratio - it'll be a few mph faster than with the 1.5 and you'll save some money... you'll have to play with props anyhow... what kind of a boat and what do you currently have on it for a prop? an aftermarket cam (the comp cams xtreme marine that's one step down from the one listed above would be perfect (262?? would have to look it up) with 1.6:1 ratio rocker arms if the heads will take the lift. add an edelbrock performer or performer rpm airgap (if you have room under the hartch) and you'll likely be pleased with the performance once you get everything dialed in.

Re: Building a performance 5.7 Engine, What parts are needed?

wca_tim said:

I'd stick with the current drive gear ratio - it'll be a few mph faster than with the 1.5 and you'll save some money... you'll have to play with props anyhow... what kind of a boat and what do you currently have on it for a prop? an aftermarket cam (the comp cams xtreme marine that's one step down from the one listed above would be perfect (262?? would have to look it up) with 1.6:1 ratio rocker arms if the heads will take the lift. add an edelbrock performer or performer rpm airgap (if you have room under the hartch) and you'll likely be pleased with the performance once you get everything dialed in.

Click to expand...

I have a '94 Regal Valanti 20' bowrider. It has the 1.84 ratio gear. With a 23 pitch prop I turn 5000 RPM and 49 MPH with a light load.

Re: Building a performance 5.7 Engine, What parts are needed?

are you certain your tach and speed are accurate? that would give you 17% slip. It would make a lot more sense if your tach was off a bit and you were really turning 4600-4800 rpms. either way, assuming you ran that gear ratio, say could hit 60 mph by gps with your new 350 and target your redline at 5000 rpms with a slip of 12% at wide open throttle, you'd need something like a 25' - 27" prop. that would be a nice sweet spot for all around performance....

Re: Building a performance 5.7 Engine, What parts are needed?

wca_tim said:

are you certain your tach and speed are accurate? that would give you 17% slip. It would make a lot more sense if your tach was off a bit and you were really turning 4600-4800 rpms. either way, assuming you ran that gear ratio, say could hit 60 mph by gps with your new 350 and target your redline at 5000 rpms with a slip of 12% at wide open throttle, you'd need something like a 25' - 27" prop. that would be a nice sweet spot for all around performance....

Click to expand...

I am pretty sure the tach is accurate and that is a GPS speed. Is the 1.84 outdrive more prone to damage with the 350 vs having the 1.47 ratio?

Thanks for your help!

Re: Building a performance 5.7 Engine, What parts are needed?

jserr68594 said:

I am pretty sure the tach is accurate and that is a GPS speed. Is the 1.84 outdrive more prone to damage with the 350 vs having the 1.47 ratio?

Thanks for your help!

Click to expand...

Less probably... the teeth are about the same size in the upper gear case, and having the slightly higher gear reduction probably transfers a little more of the torque to the lower drive (the upper is probably most prone to failure). I ran a 1.8 gear alpha behind a 400+ horsepower 383 for a good while and turned it up to 6000 rpms more than a few times and I have a fairly heavy throttle hand... the gear set that is weak and most prone to fail is 1.6. you do turn the water pump a little slower with the 1.8 vs the 1.5, but I've never had any problem with overheating even running it hard for long periods of time.

Mercury selects the best gear ratio for all around use behind a given engine - not necessarily for the best performance in a specific situation. note also that for where you're headed performance wise, you'll get a bit better performance from a prop in the 27" range than one in a 23" range. modern props that have a pitch / diameter ratio of something like 1.7 - 2.0 are generally better performing... ie a 27" mirage has a diameter of a little over 14" and is a great all around prop.

I'm no expert, but that's my understanding and my experience...

Re: Building a performance 5.7 Engine, What parts are needed?

If you're going to rebuild the short block, why not just put in the bigger crank and make a 383? I just finished my first season running a 400+ horsepower 383 through an alpha gen 1 drive and had zero problems. You have a gen 2 which is even stronger than the gen 1. I was easy out of the hole but I pushed that drive through long runs at 65 mph turning 5200 rpms and never had a problem.

As far as the thru-hulls are concerned, many people say that they don't add anything for a small block. But I run a captains call and definitely notice a boost of 150-200 rpm's every time I open them up while at full throttle. Might be because I'm running a powerful 383 and not a stock 5.7. Not sure about the drive cooling but a gear lube temperature gauge is on my list of things to do.

Check out the thread in my signature - the pictures don't seem to be working anymore, but it contains information on every part I used, assembly help from everyone and all of the problems I ran into. It might be worth your while to take a look.

Re: Building a performance 5.7 Engine, What parts are needed?

dennis moore - small block chevy marine performance - AbeBooks

Re: Building a performance 5.7 Engine, What parts are needed?

Thank you for your input everyone!