Small block vs Big block

[tazdad]

I,m looking to buy a 2000 - 2002 24 ft cuddy. I want to be able to ski and I,m getting differing opinions on weather to go with the 5.7 or the 7.4. Does the 5.7 have a better hole shot? Does the Big block sacrifice on plane time for top end. Need to hear opinions from someone thats not trying to sell me something! Thanks!!!

 

[Bondo]

Re: Small block vs Big block

A Big Block will Out Power a Small Block, From Begining to End,........
Hands Down........

A 350 Might do the Job,....... A 454 Will do the Job.......

 

[bekosh]

Re: Small block vs Big block

There is no replacement for displacement. 8)
Big block, hands down.

 

[Zackman]

Re: Small block vs Big block

I have a 22.5' foot cuddy with the 350 Mag and Bravo 3 drive. The weight of the boat is around 4200 lbs. This motor and drive does an excellent job with this hull. The big block was an option, it is a great choice for some people. I remeber reading somewhere that the average boater spends less than 6% of the time at WOT.

The boat I have also came as a bow rider and here are the Mercruiser test results. I get identical results with the cuddy.

The link to the 225 BR w/350 MAG and Bravo 3 Drive
http://northamerica.mercurymarine.c...erndrives/350MAGMPI_Crownline225BR_0304.pdf

For the 225 BR w/496 HO and Bravo 3 Drive
http://northamerica.mercurymarine.com/_media/pdfs/bhb/sterndrives/496MAG_Crownline225BR_0304.pdf

From what I heard, on this boat, the 350 Mag with the bravo 3 gets on plane quicker than the big block with the bravo 1, but after about 30 mph, the big block with all the extra torque, takes over. Again, I do not know this from personal experience only from what I have been told.

 

[Silvertip]

Re: Small block vs Big block

6% of the time at wide open throttle? They've never ridden with me! 8)

 

[Bondo]

Re: Small block vs Big block

350 Mag with the bravo 3 gets on plane quicker than the big block with the bravo 1,

I would Think, that the Difference in Drives is the Reason in This example......

 

[Zackman]

Re: Small block vs Big block

Silvertip must be above average.

Bond-o makes a good point that that drive should be considered along with the motor.

 

[tazdad]

Re: Small block vs Big block

Silvertip must be above average.

Bond-o makes a good point that that drive should be considered along with the motor.

The drive I'm looking at is the Bravo III or the VP duoprop

 

[Texasmark]

Re: Small block vs Big block

Engines have their own torque curves; part of the specs for their design. Torque is a result of that engine design and I think it is adequately recorded in text, on the road (18 wheelers) and on the track, that cubes (barring anything else) will get it for you.

But you also have to consider the torque multipliers......gear ratio of the lower unit/outdrive and prop pitch (prop gear ratio). It's a package just like in any other machine. The difference is that boats are pretty much stuck to one gear (porting the prop helps to give you some relief) whereas road vehicles have the option to change them.

So in a boat, I think the real answer you are looking for is how well does your package deliver it's torque over the desired/required rpm range. The best way to answer that question is to "test em before you buy em".

Mark

 

[JasonJ]

Re: Small block vs Big block

A 24 ft cuddy is a pig in the water. Unless you are a hardcore seasoned skier that could pop up behind a 12 footer with a 5 horse, you will want the big block for the much superior holeshot. Plan on doing any boarding? the hull should throw a decent wake but you will need the ability to hold plane at boarding speeds which are somewhere in the low to mid 20 miles an hour. Might need trim tabs to hold plane at that low of a speed. If you are not boarding, don't worry about it. Good luck...

 

[wvit1001]

Re: Small block vs Big block

I've got a 22' open bow with a 350 and it does very good at tubing and skiing. I have some good size people using the boat so I put a high-5 prop on it to get more holeshot out of it. It pulls like a tractor now and I only lost a couple mph on the top speed. A 24' boat would probably be OK with the 350 but the bigger engine could only help out more.

Whichever motor you get plan on using lots of fuel when your pulling tubes and such.

 

[tommays]

Re: Small block vs Big block

No expert but Big Blocks have there own set of problems with riser height and such on smaller boats were there really is not enough space to get as much hight above the static waterline with the extra weight in the stern


Tommays

 

[QC]

Re: Small block vs Big block

You might get away with the small block if it is a twin screw drive. There is no question that you will be happier with the performance of a big block of a higher rating. My biggest concern as always is nobody is talking about the horsepower rating. Yes, BS Man's 350 Mag is good with a B3, but what about a carbed 250? Both are small blocks, but I guarantee the Mag will blow the carbed unit away (chances are you'll never find a carbed 5.7 with a B3 anyway, but maybe a duo-prop).

Here is some good test data for comparison purposes, but the old small block/big block thing is a little blurrier nowadays . . .

http://www.stingrayboats.com/products/reviews/tb2_99.html

If it was me, I'd be way happier in equal boats with a 5.7 320 bhp Volvo, than I would a 310 Big Block same drive. However, If you compare a carbed 250 5.7, to a 385 454 MPI, then this is a stupid discussion. I guess the point is, that although displacement matters, these days the rating matters more . . .

 

[Mischief Managed]

Re: Small block vs Big block

That Stingray SB vs BB test linked above has a serious flaw. They never changed drive ratio or props. To think a 350 MAG and a 7.4 MPI would use the same drive ratio and prop in the same boat is ludicrous. The 7.4 was running at the rev limiter with the SB props. Duh...

Anyway, I don't think you'd be unhappy with a 350 MAG instead of a 7.4 MPI in a ytypical 24 foot boat. The 7.4 MPI is not a water sports engine (it's more of a cabin cruiser engine made to get heavy boats on plane with fairly low RPM using steeply pitched props), IMO. If the BB choice was a 454 MAG though, well, that would rock.

 

[QC]

Re: Small block vs Big block

MM,

I agree on the flaw, but it is hard to find good data from two identical boats. As is, it still illustrates a lot.

Although I continue to beat this well beaten horse, the horsepower rating is the most important number on a marine engine. Not the only important number for sure; so is weight, peak torque to a small degree (larger issue for ski boats), displacement (more of a fuel efficiency issue with bigger being worse) and RPM etc. It was just interesting to me that only Jackman's post refers to the rating, and that was inderectly.

We totally agree on the 454 MPI, yeah baby!!

 

[RubberFrog]

Re: Small block vs Big block

Tazdad, you'll be fine with the 5.7. You'll probable have more fun with the BB though. Don't believe this nonsense that you need a BB for a 24' cuddy. That's old school thinking. Modern engines have so much torque and hp compared to engines of yester-year it's not even funny.

I pull skiers on a regular basis with my 25' /5.0 mpi. And not very good skiers, either. Would I like a BB? Sure. Is boat my boat a "pig in the water?" Absolutely not.

Buy the biggest engine you can afford. You'll be happy with either one.