gas mileage: 3.0 vs 4.3

[jonmyrlebailey]

all else equal in a 21-foot Bayliner, how much worse is the 4.3 190-hp going to be over the 3.0 135-hp in gas mileage at optimal cruising speed for each motor?

are 3.0's difficult to find in 21-foot boats in California used?

is a 3.0 too small for a 21-foot hull?

 

[QC]

Re: gas mileage: 3.0 vs 4.3

all else equal in a 21-foot Bayliner, how much worse is the 4.3 190-hp going to be over the 3.0 135-hp in gas mileage at optimal cruising speed for each motor?

Not worth counting. Very close at "cruise speeds".

are 3.0's difficult to find in 21-foot boats in California used?

Difficult to find anywhere.

is a 3.0 too small for a 21-foot hull?

Yes. 33 MPH boat.

Next issue, Jon?

 

[Don S]

Re: gas mileage: 3.0 vs 4.3

I don't think you could get a 21 foot fiberglass boat of any kind on plane with a 3.0L unless it was paper thin hulled (like some of the early bayliners) they were scary.

In the real world, you will get better mileage with bigger engines. They don't have to be at wide open throttle and full power to get on plane at minimum speed.

 

[aerobat]

Re: gas mileage: 3.0 vs 4.3

don, with all respect- what you write here seems not to be valid to me.

i have a 21ft cabin boat , rougly 3200 lbs so not a paperthin bayliner and can assure you first hand the 3.0 WILL bring it on plane, even with 4-5 adults on board. ( volvo 3.0 GS )

if its enough - thats a question of personal taste. when you can live with having a roughly 30mph top speed its enough, otherwise not.

gas milage tends to be nor better neitehr worse than with a bigger engine. its neither fantastic nor dramatic on the 3.0.

without any doubt the 3.0 has to work hard on a 21footer. going on plane with it dictates to be at or close to full thrlottle all the times.

cheers

 

[jonmyrlebailey]

Re: gas mileage: 3.0 vs 4.3

Ideally, I would like to cruise at 25 knots with the motor no more than 3/4 throttle, so probably the 4.3 190 is the best bet in a 21-foot runabout to cruise all day long without strain. Will a 350 do considerably worse than a 4.3 in a 21-foot runabout? I read that a boat has to be just at a speed where it is solidly on plane to get the best on gas.

I have also heard that 3/4 throttle is ideal.

Then there is the math formula (I don't know if it holds "sea" water):

for carbs, divide horsepower by ten and then again by two to get gallons per hour at cruise
for EFI, divide horsepower by eleven and then again by two to get GPH at cruise

I have seen some chart with even 4.3 and 350 V-8 getting over 4 miles per gallon at econo-speed cruise with the 3.0 closer to 5 miles to the gallon.

 

[ENSIGN]

Re: gas mileage: 3.0 vs 4.3

If you're going to be worried about gas mileage,don't buy a boat.

 

[QC]

Re: gas mileage: 3.0 vs 4.3

jon,

I have a suggestion. Go here: www.BoatTest.com find all of the data you want, forget the wives tales, and rules of thumb. Look at the data and make a choice. When you go from a 3.0 to a 5.7 in the same thread while coming back about fuel sipping cuddies again, well . . . get the data there and be done with it.

Good luck.

 

[tahoejag]

Re: gas mileage: 3.0 vs 4.3

If you're going to be worried about gas mileage,don't buy a boat.

Sounds to me that he is "curious" about fuel consumption and not "worried" about it...as would any boater in this fine economy that we now face with today's fuel prices. Heck, I would gladly allow the individual that has no regard to today's fuel prices to fill my boat up anytime!

As for the consumption of fuel...It would be a matter of how u run your boat and how deep your into your throttle, pulling skier, load, etc.

 

[aerobat]

Re: gas mileage: 3.0 vs 4.3

Ideally, I would like to cruise at 25 knots with the motor no more than 3/4 throttle, so probably the 4.3 190 is the best bet in a 21-foot runabout to cruise all day long without strain.

25 knots will be about full speed on an average 21ft cabin cruiser with the 3.0 . but the ( volvo ) 3.0 runs full throttle all day long without any issues. so eiter accept this as your top speed with the capability to use it as continous cruise or truly go for at least a 4.3 .

and some words to fuel prices... are you fellow americans crazy ???? we in germany pay rougly double your price for the gallon, people in UK more.

i understand that its a shock what happened to gas prices the last two years to you, but it is still very cheap in comparision to europe !

obama or romney in three weeks ?

 

[QC]

Re: gas mileage: 3.0 vs 4.3

Hi aerobat. I travel a lot Internationally and chuckle at my American Bros a bit too. Fact is that we all pretty much use our own situation as the barometer...

Sorry, but we don't do politics here. If we did I'd tell you that I am pretty sure JB voted for Teddy Roosevelt.

 

[jkust]

Re: gas mileage: 3.0 vs 4.3

i have a 21ft cabin boat , rougly 3200 lbs so not a paperthin bayliner .

I think this is a perception issue as I perceive a 21 foot cabin that weight only 3200lbs to be severely underweight by modern norms.

 

[aerobat]

Re: gas mileage: 3.0 vs 4.3

@ QC - you,re right - boating is more fun than politics !

@jkust : not really,

stingray cabin 21 ft : 2950 dry

http://www.boattest.com/boats/boat_video.aspx?ID=1769

chaparall 21ft: 3500 lbs dry.

doral 21ft : 2750 dry.

3200 lbs dry is pretty common. bow riders tend to be lighter, cabin boats a little heavier. and of course it depends what an engine you have . when the one has a 3.0 and the other a 5.7 the difference in weight is about 300 lbs alone due to the engine and has not nothing in common with boat construction...

 

[Don S]

Re: gas mileage: 3.0 vs 4.3

You guys might want to look at the other threads the original posters has started. Then you might see why he is asking this, and get a better understanding of what he is wanting in the long run.

 

[Bondo]

Re: gas mileage: 3.0 vs 4.3

You guys might want to look at the other threads the original posters has started. Then you might see why he is asking this, and get a better understanding of what he is wanting in the long run.

Ayuh,.... or not....

My take on fuel economy is this,...

It takes a certain number of btus to move a hull, 'n load through the water at a certain speed...

Regardless of what yer burnin', 'n makin' those btus with don't really matter, so long as the btu number is the same, the economy is the same....

 

[wca_tim]

Re: gas mileage: 3.0 vs 4.3

The only relevant experience I have is that each time i switched to a higher compression more efficient engine in the same hull, I gained fuel economy at the hulls sort of optimum cruising speed (somewhere around 35 mph or so). more efficient engine, better fuel economy. all other things being equal, what Bond-O said... doesn't make a lot of difference if all is in good repair.

That being said, you can always run a bigger engine slower, but a smaller one can only go so fast... Also, in my experience, running a bigger engine under a lighter load rather than a smaller engine under a heavy load is a good thing when it comes to longevity...

 

[HT32BSX115]

Re: gas mileage: 3.0 vs 4.3

The only relevant experience I have is that each time i switched to a higher compression more efficient engine in the same hull, I gained fuel economy at the hulls sort of optimum cruising speed (somewhere around 35 mph or so). more efficient engine, better fuel economy. all other things being equal, what Bond-O said... doesn't make a lot of difference if all is in good repair.

You clearly REDUCED your BSFC by increasing the compression ratio! changing to EFI, improving the volumetric efficiency, using synthetic oil in the drive, more efficient propellers, a clean bottom (of the boat) and other friction reducing stuff also helps!

 

[Bamaman1]

Re: gas mileage: 3.0 vs 4.3

Just go with the very popular 4.3 motor. I've never heard any complaints about the fuel mileage. It's a great compromise of power and fuel mileage.

The 3.0 does okay when the boats get up to speed. They're just pretty lame coming out of the hole. A good set of hydraulic trim tabs would help them substantially in acceleration. But most I/O's will run okay on top end.