Mercruiser 5.7 or 5.0

[russ]

Hi all
My search is still continuing for the right boat and after missed opportunities on various craft I'm now considering petrol as a newer boat purchase as apposed to an older diesel.
The question, is the Mercruiser 5ltr anymore economical than the 5.7ltr?
Just wondered if the 5.7 would be under less stress and maybe the better engine.
Though my first year or so will be on the river so may not be much between the two?
Secondly the 5ltr is with a Bravo 1 drive and the other with a B3 on the 5.7ltr.
I'm guessing the 3 is best?

 

[dingdongs]

have a 5 litre in a 20ft bayliner used for watersports so gets a little more un economical through the extra drag but a 6 to 8 hour day will see you about £80 lighter.if your talking about a cruiser which may not be used in this way it may be better to go for a 5.7 for the extra horses as 40hp minimum is nice to have but vessel may be heavier and probably more bodies on board and extras.

 

[moonraker 36]

5.7 everytime.....

 

[AndieMac]

They are both good engines, but if you maximise the vessels load carrying capacity reguarly, the 5.7 will be the 'gruntier' option, especially if hole-shot is important to you.
I have recently repowered from a 5.0 to a 5.7 because of big load carrying etc., with very satisfying results.

On the drive thing, I understand the Bravo 1 and the Alpha, share the same size prop shaft, so at least the props will always be affordable, compared to B2 and B3.

 

[MapisM]

the Bravo 1 and the Alpha, share the same size prop shaft

Correct AM, aside from the XR version of Bravo I which has a larger shaft - but I've never seen a small block fitted with an XR drive.

I'll second both the recommendation for the Bravo I and for the 5.7 block.
The Bravo III could only make sense in a single engine boat, IF maneuverability is a major concern. Other than that, the B I is better in all respects. And the B II is not even worth considering, because it's just for slowish heavy boats, where high load at low revs demand a larger prop.
Re.the block, with planing boats the rule is very simple imho. Whenever among engines of similar weight there's one available with higher power, go for it. Assuming of course that they're also comparable from a reliability viewpoint, as is the case with the 5.0 and the 5.7.
In fact, the consumption depends more on the hp the prop demands (which doesn't change for any given speed/hull/weight), than on the total power the block can deliver.
So, the 5.7 means higher power reserve, better holeshot, higher top speed, with a negligible consumption difference at normal cruising speeds.

 

[Kipper]

5.0 v 5.7 depends on size and weight of boat really, but Bravo1 every time if you can though unfortunatky a lot of 5.7 efis have bravo 111's on them. not a bad drive compared to volvos but annual maintainance is essential.

 

[mateyboy]

Defo 5.7 uses same fuel as 5.0 , no brainer owd cock.