5.7l vs 4.3l fuel usage?

[thumpar]

As I am looking at boats I really want a 5.7l but I am concerned about the fuel usage. We have a 120hp now and know that anything bigger will use more fuel. Normally we just cruise down the lake to our favorite spots 10-15 miles down. I want to get there faster but don't want to spend a ton on gas. How big of a difference is a 4.3l and 5.7l on gas at cruising speeds of 3200-3800 RPM? This would be in a 19-20' open bow.

 

[carribbean soul]

Re: 5.7l vs 4.3l fuel usage?

you want to go from 120hp to 300hp! Good for you you will need a different outdrive gear ratio and a bigger prop. does the engine compartment have the space for the re-power?

 

[thumpar]

Re: 5.7l vs 4.3l fuel usage?

I said I am looking at boats not repowering. The 120hp boat is finding a new home.

 

[chimmike]

Re: 5.7l vs 4.3l fuel usage?

The way I see it is, your consumption is not going to increase on an exponential factor. The boat may not be significantly larger, but the added power will allow it to not have to work as "hard" to maintain x speed as say the 4.3 would. It's still going to consume more, but if everything is right, boat is waxed and on plane, etc. etc., it most certainly should not hurt the wallet.

 

[Scott Danforth]

Re: 5.7l vs 4.3l fuel usage?

go to boattest.com and look up the boats your interested in. they do real world fuel economy testing, usually with two people on board.

 

[carribbean soul]

Re: 5.7l vs 4.3l fuel usage?

I said I am looking at boats not repowering. The 120hp boat is finding a new home.

sorry, my 454 with a bravo 3 gets 18gph with a 24knot cruse and can go as high as 33 gph

 

[KD4UPL]

Re: 5.7l vs 4.3l fuel usage?

There won't be much difference. If you're that worried about fuel consumption boating's not the hobby for you.
A given weight and shape hull going a certain speed will take basically the same amount of HP and thus fuel. It doesn't matter as much as you might think what size engine is being used to deliver that HP.
Get the big engine. You can never have enough HP in a boat.
For reference, my 20' open bow has a 210 HP 5.7L engine. I can cruise, ski, tube, etc. for about 6 hours on roughly 20 gallons of gas.

 

[thumpar]

Re: 5.7l vs 4.3l fuel usage?

There won't be much difference. If you're that worried about fuel consumption boating's not the hobby for you.
A given weight and shape hull going a certain speed will take basically the same amount of HP and thus fuel. It doesn't matter as much as you might think what size engine is being used to deliver that HP.
Get the big engine. You can never have enough HP in a boat.
For reference, my 20' open bow has a 210 HP 5.7L engine. I can cruise, ski, tube, etc. for about 6 hours on roughly 20 gallons of gas.

I have been boating since I was 6 so I know the costs. I was just wonder how much the difference was.

 

[Volphin]

Re: 5.7l vs 4.3l fuel usage?

As I am looking at boats I really want a 5.7l but I am concerned about the fuel usage. We have a 120hp now and know that anything bigger will use more fuel. Normally we just cruise down the lake to our favorite spots 10-15 miles down. I want to get there faster but don't want to spend a ton on gas. How big of a difference is a 4.3l and 5.7l on gas at cruising speeds of 3200-3800 RPM? This would be in a 19-20' open bow.

I've had a 5.7L, and have a 4.3L now. The 4.3L is a better deal IMHO as far as fuel use. I'm also in the same size boat... measures 21' overall. I noticed when she was able to breathe properly, that fuel consumption went WAY down @ cruise. I changed to a 4 barrel and intake. I could run a 28 gallon tank all weekend with some to spare for next...
That's tubing, long cruises and visiting friends a long way away.

 

[Lou C]

Re: 5.7l vs 4.3l fuel usage?

I have a 4.3 4bbl Cobra and its very economical because it runs most of the time on the 2 small primary venturis of the Rochester Quadrajet. However, the difference is really not significant, I would take the V-8 because lets say that the V-6 saves you maybe 2 gallons per hr (like 8 vs 10) but the V-8 is more pleasant to drive, then the consumption difference will not really matter. But I think its around 2 gph or so at most. The 4.3 is 6/8ths of a 5.7, same bore and stroke but 2 less cylinders.....
I'd say that in a 18 footer, the 4.3 is fine, and fits nicely for routine maintenance. In a 20' the V-8 might be a better choice and also might be better for resale.
I saw a 16 foot Donzi "Sweet Sixteen" for sale locally with a 5.7/Cobra, now that little boat would be FUN....

 

[HT32BSX115]

Re: 5.7l vs 4.3l fuel usage?

sorry, my 454 with a bravo 3 gets 18gph with a 24knot cruse and can go as high as 33 gph

The 454/Bravo III in my 21' Liberator does 10gph at 3000 RPM (30mph GPS) on my Lowrance fuel flow meter.


It's all largely based on the SIZE of the boat!


If you put a 5.7L engine in a simiarly sized boat with the same weight and hull shape, it will use approx the same fuel at approx the same speed with various sized engines.

The extra fuel flow would be due to your "right hand" ! because if ya got it, ya use it!!!

Originally Posted by KD4UPL
Get the big engine. You can never have enough HP in a boat.

10-4 GOOD BUDDY!!

 

[thumpar]

Re: 5.7l vs 4.3l fuel usage?

I ended up getting the 5.7l. It even has a Bravo I behind it.

 

[Fun Times]

Re: 5.7l vs 4.3l fuel usage?

I ran across this fuel consumption meter a while ago, it's kinda neat to check out.

Looking for a boat ? Check fuel consumption all types of boats !

 

[thumpar]

Re: 5.7l vs 4.3l fuel usage?

I ran across this fuel consumption meter a while ago, it's kinda neat to check out.

Looking for a boat ? Check fuel consumption all types of boats !

I found that a while ago. The only thing that is not taken into consideration is drive ratio. The prop on a V6 is going to be spinning slower than a prop on a V8. I wish they would do something like that for prop RPM so that it is more comparable.

 

[philipp10]

Re: 5.7l vs 4.3l fuel usage?

Your going to have a lot of people tell you there is little or no difference. They are right, AND wrong. If you go to boattest, you will see at cruising speed the larger engine will probably take 15-20% more. The weight of the larger motor would do that alone. However, there is much more to the story. If you do any boating like I do, we cruise maybe 1/3 rd the time and putter around at 1000 rpms 2/3rd the time. What you will see at boattest is, fuel consumption will probably double. I was looking at the difference between a 3.0L and a 4.3L and with my style of boating, the 3.0L uses 1/2 the gas. The only fix for the larger motor would be is you had a small kicker to use at slow speeds. Of course, that is hardly practical.

 

[Walt T]

Re: 5.7l vs 4.3l fuel usage?

Thumpar, what boat did you get? That the '96 Crownline? Pictures?

 

[thumpar]

Re: 5.7l vs 4.3l fuel usage?

Thumpar, what boat did you get? That the '96 Crownline? Pictures?

We only got a use it a few times last year before the weather got bad so we don't have many pics. The new boat is the boat in my sig. Here are a couple pics from the seller. The angle makes it look smaller than it is.



This is one my wife took.



I think the kids like it.

 

[Walt T]

Re: 5.7l vs 4.3l fuel usage?

Sweet! The 5.7 is perfect for that size.