Outboard Efficiency

[commander315]

Exactly how much more efficient are outboard engines? Now im running 27 yr old Mercrusier 350's (260 hp each) , Im looking at a 2008 35' boat with Triple Yamaha 250's. Are these engines significantly more efficient then inboards (Especially mine)

 

[mpsyamaha]

Re: Outboard Efficiency

if you are pushing three 250s hard, whether they are 2 or 4 stroke, you will burn some serious fuel, i would think like 75gal/hr or more at WOT. but, if its a fast boat it could be pretty efficient at cruising speeds and lower rpms. also, if you provide more detailed information you could probably get more answers.

 

[commander315]

Re: Outboard Efficiency

if you are pushing three 250s hard, whether they are 2 or 4 stroke, you will burn some serious fuel, i would think like 75gal/hr or more at WOT. but, if its a fast boat it could be pretty efficient at cruising speeds and lower rpms. also, if you provide more detailed information you could probably get more answers.

i agree...Its a 2008 Wellcraft 35 Scarab Sport (8600lb dry) w/ 2-200gl fuel tanks. (I would probably get an awesome deal on it, btw) My engines now burn crazy fuel only doing 20mph, (Its startin to tick me off a bit) ..even if i break even...ill be goin 3x as fast..so thats not bad..right? Plus, the new boat wouldn't be as much of a money pit... i hope

 

[mpsyamaha]

Re: Outboard Efficiency

you will definitely go a lot faster burning the same amount of fuel, but overall fuel consumption will still be a fair amount. i mean after all we are talking about 750 hp.

 

[kenmyfam]

Re: Outboard Efficiency

That kind of fuel consumption scares me !!
Good Luck with your decision. It would maybe cost what I spend in a day on fuel to get out of the no wake zone

 

[45Auto]

Re: Outboard Efficiency

Tests with mid-30' boats with triple Yamaha 250's show best cruise at about 30 MPH while getting a little less than 1 MPG. Top speed is in the mid-40's, burning 60-70 GPH.

I would expect your Chris Craft probably gets in the neighborhood of 1 MPG at best cruise, so your only real savings would probably be the time you save getting where you're going between the new boats best cruise speed and the Chris Craft's best cruise speed.

 

[mpsyamaha]

Re: Outboard Efficiency

im not sure of the numbers on the exact boat you are looking at, but the speeds 45auto listed seem slow. the boat you are looking at should move pretty good with 3 250s. and the 1mpg at cruising speeds seems about right from what ive seen on larger outboard powered boats.

i know we have a 35' marlago with twin 300 yam hpdi that will do right at 60mph at WOT, but its burning 60 gal/hr with only 2 engines. then again, at work we also have a 35' hydrasport that is a much heavier and wider boat with twin 350 yams and it burns about the same fuel but only does mid 40s.

 

[commander315]

Re: Outboard Efficiency

Its top speed is approx. 58 and its average cruising is set around 42. (Wellcraft says this higher cruising speed is because SCARAB is a High performance boat...) Heres some stock pics from wellcraft (Ignore the 300 Merc verados)Wish me luck !! and thanks for the feedback

 

[180Fisherman]

Re: Outboard Efficiency

I always thought an outboard was less fuel efficient than an i/o. All else being equal.

 

[commander315]

Re: Outboard Efficiency

I always thought an outboard was less fuel efficient than an i/o. All else being equal.

idk thats not what i heard...I also dont have stern drives. I heard a lot of mixed stories but believe that both I/O's and OB's are both more efficient that regular inboards. Where it goes from there im not sure. Also One other side question, Mercury Verado Outboards are supercharged, how does this affect their efficiency?

 

[capt sam]

Re: Outboard Efficiency

we run a Verado on our work boat, it does pretty well on fuel. Three will suck fuel either way but you will have fun doing it.

 

[NelsonQ]

Re: Outboard Efficiency

idk thats not what i heard...I also dont have stern drives. I heard a lot of mixed stories but believe that both I/O's and OB's are both more efficient that regular inboards. Where it goes from there im not sure. Also One other side question, Mercury Verado Outboards are supercharged, how does this affect their efficiency?

I did a comparison of my 200 HP 2 stroke Optimax vs the 200HP 4 stroke Verado.

The fuel consumption was negligible, with the Optimax more efficient on the lower and higher RPMs, the Verado better at the mid ranges.

Biggest difference was the cost to purchase/repair. Verado is higher.

Verado is quieter than the Optimax.

I opted for the Optimax because the fuel consumption (for my usage) wouldn't be worth the extra purchase price and having a supercharger to produce better low end torque that the 2 stroke provides naturally didn't make sense. Another expensive piece to fix.

 

[dingbat]

Re: Outboard Efficiency

I always thought an outboard was less fuel efficient than an i/o. All else being equal.

The Yamaha 250's is a 3.4L 4 stroke. The same size I/O buys you nothing but a higher weight to HP ratio and a more complicated drive train.

 

[QC]

Re: Outboard Efficiency

I always thought an outboard was less fuel efficient than an i/o. All else being equal.

Old carbed 2 cycle OB v.s old 4 cycle I/O = true
Old carbed 2 cycle vs. newer MPI I/O = waaaaay true
Newer EFI OB 2 or 4 cycle vs. newer MPI I/O = not true

I heard a lot of mixed stories but believe that both I/O's and OB's are both more efficient that regular inboards.

Generally true. Conventional Inboards are the worst combination for speed and efficiency. Trim is a BIG deal. Jet drives may even be better.

Also One other side question, Mercury Verado Outboards are supercharged, how does this affect their efficiency?

Superchargers (and turbochargers) generally help with power to weight ratios. It's called "power density" and forced induction is theoretically better. It's an attempt to keep up with 2 cycle power to weight ratios that are typically very good. Fact is that modern 2 cycle and 4 cycle OBs are very close in real world fuel efficiency as the 4 strokes are heavier and modern 2 cycles are very good keeping them close enough for a push due to their lower weight.

 

[commander315]

Re: Outboard Efficiency

Thanks for all the insight!!