Big cubic inches or blower for 650-700 hp? Carbed or fuel injected?
 

just for pleasure of taking engine! Lets say you wanna have at least 600 hp, but mainly 650-700 hp...
we all know a 500 efi with a bolt on whipple runs around those number between 650-700, not sure about real numbers...
i also remember it is not overthinking a 540 can push 650 ish reliable hp
gm makes 620 hp and or 720 hp on race gas from 572 cubic inches. And i remember someone on the board had 632's cubic inches but cant remenber how many hp he was pushing.

So many ways to play around those hp numbers

if you were to choose a recipe, what way would you choose? No replacement for displacement? Or blower? , keeping in mind dock friendly, and stay far from reversion, and cost of maintenance!

While we are at it, carbed? Or injected? And why?

Blowers. For 600-700 N/A is fine. Above that I'd go blowers. Also depends what you're starting with.

I am having a 540 built that should be about 650 HP. I hope that the NA motor will be more drive friendly. If I need more, I can Whipple it. Bottom end built to stand 1000 HP and that much torque. 650 should push 29 Fountain 80ish. Will know by spring or on a warm day this winter. Holley EFI instead of carbs.

I currently run a N/A 548 in my 30ft boat and it is really easy to drive but I have no space for pulleys to install a blower. I run at high altitude so a blower would actually help me out a lot but a boat at sea level will have plenty of air. I come from drag racing and was expecting to see more of the big cubic inch 632's and even larger N/A motors in these big boats. Pretty easy to get 900-1000 HP these days with a single carb on pump gas with a 632.

we ran a clone 500HP with a MS3 procharger with both 2 different carb setups, one in box(hated it) but ran fine hard to service, EFI, and back to blowthru carb, ran engine for almost 5 years, with blow thru carb ran great on 5-6 psi

A well built 502 with an 8-71 blower, small cam and fuel injection. It will idle like a minivan and make 700hp easily and reliably. If NA is in order, 555 or 565CI with the Holley fuel injection. It will take a little more cam than the blower motor and would stand more chance of being a little grumpy around the docks and more possibility of reversion.

I've got a pair of 540's making 675 with Dominators that I've been running for four years, (about 500 hrs). I spent a lot of money and bought the best of everything. They've been trouble free other than a rocker arm failure this year which the manufacturer ponied up with two new sets. Fortunately nothing else got jacked when the rocker broke. While the Dominators have performed well I'd be willing to give up a few HP for the fuel economy of EFI.

what rocker arms if you don't mind me asking?

Scorpions. They sent two sets without asking for the old rockers to be returned. All they asked for was a pic of the broken rocker which I emailed to them.

Carbed roots blowers for that HP level. They look and sound fantastic. Your power band is as wide as the country side and everything is kept simple. We had Edddie Young build/tune one and it idles all day and fires with a quick turn of the ignition switch.

Made 725 with 598s carb and NA on 87 pump gas.

C.I.
 

GT Performance just Dyno'd one of two of my engines that they built 588 C.I. Normally Aspirated with Emtron KV8 ECU, Sequential FI, Closed Loop Fuel Lambda sensors 740 HP
on 87 Octane.

700HP and under N/A

650HP+ Forced Induction

aggressive cam? I still have my Scorpions, I have valvetrain more under control now over what I had before, I admit.... I am worried at times about the Scorpions, then I figure with girdles and all I should be ok... I hope.

If I did what I did again, I would do 502 or whatever with forgfed internals, decent heads and BOOST.... you work the parts so much less to make the same HP, nothing is custom or maxed out, Eddie Young and I had a conversation about this after I got mine done, he pointed out... mild cam, mild springs, no crazy heads needed... just boost and good fuel system...

Tuned right blower motors can be very friendly . 900 hp and I idled around for at least an hour Saturday ( prop hunting) then went down the Chicago river for another 40 minutes of idleing.. never fouled a plug or missed a beat .

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Plus I mean look at those things , it`s boner city :drink:

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If I had one complaint it`s that it sounds like someone killing a cat in my bilge all day long.

What rpm are you planning on turning them?What outdrive?

Big cubes + big blowers = big horsepower + big money (and yes, boner city)

Big cubes NA + efficient hull = fast + reliable boating

(my two cents after owning, operating, and maintaining the former)

Also wet or dry exhaust?
If you are building one that is dry exhaust and turning 5500 rpm then a naturally asperated one will do the job quite well.

If you are wet exhaust or turning it over 6k then I would do a blower.

With an na engine it's hard to get them to idle well and have big numbers at 6000 or above.When you get them to not stall at the dock then 6k and above torque drops like a rock.

But with a blower you can have a smaller cam and still pull at 6k and above.Which gives you good idle and still pulls at higher rpms.

Also with A N/A engine has wet exhaust you are seriously limited on duration and valve overlap.Which means that you would have to run a smaller cam.Which then the engine would only make good torque up to about 5000 rpms.

Hope this helps

Agree...lol..

Not terribly aggressive, lift is just shy of .700 IIRC. To be honest I think the rockers failed because of a misfiring issue I had earlier this year. The distributor cap was trashed and it was miring multiple cylinders. I guess I should have mentioned that in my initial post.

gotcha, sucks to hear either way

At least it did tear anything else up. Back up and running so all is well.

Why not get a tall deck 10.2 block and build you own 632 ci bbc.800 hp just from the cubic inches and no blower needed
:eekdrop:

Not quite the 650hp as asked for but my 454 with good internals, hyd roller cam, 177 blower and stainless marine manifolds make 610 hp and starts and runs like a fuel injected motor. I would say not a high dollar if you already have the parts like I did but with better heads and a 502 you could easily hit the 700 hp and be very reliable.

Big cubic inch tall deck , 87 octane , iron eagle 345 's spend money on valve train stability i.e. shaft rockers , high end solid rollers . Definitely carbed maybe a short tunnel ram with twin 660's , big tube etops

​​​​​​​keep rpm to under 6k , set lash once a year , enjoy boating

While a lot of boat motors are built like drag racing motors, you can't get too crazy with boat motors because they take much more abuse than a drag motor. You don't see a lot of boat motors over 565ci because above that, the wrist pins are way up into the rings and overall the pistons are weaker. Also a more aggressive cam = water reversion in a boat. Obviously exceptions to this using big aftermarket blocks with 5" bore spacing for more cubic inches, dry exhaust for water reversion etc $$$. Overall, boat motors are built like tanks, and tuned very conservatively. My motor is capable of 1000+ hp in a car, but tuned for 825 in the boat.

For the OP, 700hp is easy and relatively cheap on pump gas NA. Above 700, blower.

I was only making an observation as I am new to boating and was used to seeing these huge cubic in motors. Believe me when I went to build my motor my machinist told me this would not be the same kind of build as my dragster and I have learned a lot reading on this site. I see a ton of expense and extra parts in blowers for big blocks and really don't see any issues with any kind of piston or any other motor parts these days with the high quality parts we can get. I see 6 page discussions on $200 valve springs and off the shelf cams from guys buying or rebuilding high dollar motors? I was also speaking to a pump gas motor and not a drag motor which can't use a high lift cam or lots of compression. Also on a pump gas motor you just tune it and drive it, you don't have to de-tune your motor. Currently for me I would love a blower since my high altitude lake is kicking my ass to make power and I have internals to take over 1500 HP but since this is my first boat I did not realize I have no space for blower pulley when I bought it.:angry-smiley-044:

If you're buying a dart big M why would you build anything less than a 598-632 with 800hp. All the components cost a similar amount.

On the 27 Advantages, they have 2 molds, one has a notch in the bulkhead in front of the motor to accommodate a blower pulley just for that reason. They probably didn't worry about that with your boat because nobody was using blower motors in those boats then lol!

The boat came with a 177 blower and has holes in the back of the seats for those tiny pulleys. So someone tried. No way was I wasting time with that small of a blower on a 540.

Blowers get my vote.

Only reason blowers are labeled problematic , is not because of the blower sitting on top. It's because of the builder. Sorry, but if you have blower engines and they are constantly breaking, it's time to find a new builder.

I have 468s making over 800hp , that idle all day long at 700rpm in gear, and scream to 6200rpm without as much as a hiccup. Basic Mark IV 454 blocks, GM forged cranks, hydraulic roller, etc. Nothing fancy. Try making 800hp with a NA 468, and you'll have a race fuel, non idling, 7500rpm untamed beast that will launch valvetrain pieces after a few passes across the lake. I am pushing the envelope a bit , but I'm good with that. If longevity was the goal, I know I could turn the boost down to 4lbs, make 675-700hp, but what fun is that :)

Did someone say scorpion rocker failure ?

I thought scorpions were one of the best.What is the next alternative
jessel?

..

I don't know about all that ....being "one of the best "....crower makes a great steel rocker and comp cams Ultra XD rockers...crane retooled their gold rockers , but I haven't seen the new versions yet

Which cam are you running? Exhaust wet or dry? I got 572 hp with stock 454 mag longblocks, 177's, single 800dp, flat tappet cam and wet emi exhaust.

My advice to you is to get a dyno program and punch in some normal specs with a cam that will not revert and see how much torque you will be making at the top rpm you want to run it.

Then switch the program to a supercharger with 8 lbs and lower your compression and see which will do what you need it to do.

Ps Forget about hp numbers and concentrate on the torque in the rpm you want to rev it to..Hp is a formula of torque and rpms.
You could have an engine that makes 800hp but makes torque to low to get on plane and in the range you would be using it.Which is worthless.

So!

opinions are not all the same!! Good points to both recipe!

Still not clear to me!

guess it depends on what the engine builder you work with prefers!

thanks for talking about all those good opinions!

Also, factor in the type of boat. A 35 Fountain, might not like the same engine as a single engine 29 fountain.

We must remember that we have an outdrive and prop that acts like a gear ratio. Let's say you build an engine for max low and midrange numbers. And setup to spin 5000rpm. You turn a 30p prop to 5000rpm with a 1.5 gear ratio.

Now you build another version of that same engine, that trades off some low rpm power, for upper rpm power, and can rev to 6000rpm. Can turn a 26p prop say, to 6000rpm. Even though you gave up some midrange or low rpm power, you may find the boat accelerates and planes better, with the 26p prop setup, vs the 30p low rpm stump puller engine.

It's like comparing a car , say with a LS small block and a 4.10 rear end, to a big block with a 3.08 rear end. Just because you're making more torque at a lower rpm, doesn't always equate to faster acceleration, or even more efficiency . In semi truck world, for getting an 80k lb rig from 0-60, I'll take a 350hp with a 13spd and 4.30 rears, over 450hp with a 8spd and 3.55 rears any day of the week.

Take a look at Bob teagues amsoil boat with its 500 inch Supercat engines that rev to 7k plus, certainly not low rpm stump pullers, but they have no problem coming out of a corner ,putting it on the limiter and coming up to speed in a hurry.

If fuel efficiency is a big concern, focus on the hull . A cat or efficient vee bottom, is gonna get much better fuel mileage than a heavy old deep vee. A pair of 750 carb engines in a cat cruising at 65mph, is gonna get better mileage than a heavy straight bottom deep vee with a pair of 525s. It takes HP to push a boat thru the water at xxx speed. It takes x amount of fuel to make x amount of HP. I've seen guys spend tens of thousands on custom efi setups and super efficient engines , chasing fuel economy from their boat , when they should have just got a modern stepped boat for what they spent.