O/b vs I/b all things equal

[QC]

Re: O/b vs I/b all things equal

Agree that ^^^^^^

 

[CharlesRiver]

Re: O/b vs I/b all things equal

I'm not basing my decision on the answers from this question, I was just considering these 2 boats, I got wondering how they would compare power wise, and fuel wise.
The layouts are very similar, the sun deck being larger on the I/b.

I'm going to look at the Larson in the next few days. The Glastrom is in storage for the next while so I can't get in to look at her.

 

[BrianCinAz]

Re: O/b vs I/b all things equal

One issue with used I/O is the cost of repairs/rebuilding the drive unit. I have seen boats of similar age to what you are considering that needed a complete overhaul of the drive. I know you didn't ask about that, but since you are concerned with operating costs, repairs must be considered.

I have a 2012 Axix A-22, V-drive Inboard 330 HP. We wakeboard, tube, ski and cruise all day and rarely use more than 10 gallons of gas. A larger engine turning a larger prop at a lower RPM will always use less fuel when tubing. I have friends with I/O's and they use double the fuel in a day that I use. Remember, cruising stats like mentioned in a previous post are only good for going from point A to point B (Florida to the Bahamas). But wake boarding and tubing are not done at cruising speed. I don't know anyone that tubes or wake boards at 30 knots.

 

[QC]

Re: O/b vs I/b all things equal

I have friends with I/O's and they use double the fuel in a day that I use.

I hesitate to blatantly contradict your post, but there is absolutely no data supporting that. I understand that pulling a tuber is different than cruising. And that low speed fuel use may be better at some points with an I/B. If there is a benefit to I/B fuel use at low planing speeds I bet it would be mitigated with trim tabs.

And for the record, theoretically, the smallest engine with a large prop will deliver the best fuel economy. DO NOT DO THIS AT HOME!! Can be a disaster over extended periods. Conversely, operating a large displacement Otto cycle engine (four stroke with spark plugs) at light load results in the worst fuel efficiency over it's operating range. The large wheel helps mitigate this, but then you risk a lug condition which Otto engines don't like

I have a 23 footer, 320 horse, Bravo 1. With your AZ suffix I assume you are in Arizona. We should follow each other around some day and compare fuel use. My boat is at Havasu.

 

[airshot]

Re: O/b vs I/b all things equal

To answer your last question, yes the 2 stroke OB will use more fuel than the I/O when compared in mpg. 2stroke engines use more fuel unless they are of the newest design. Many good points have been made on here, these are all things to consider. Overall condition and maintaince on a used boat is most important over fuel usage. My 140 hp I/O in a 22' aluminum boat uses the same amount of fuel as my 50 hp outboard did on my 16' aluminium boat. I do have much more maintenence on my I/O, which I am able to do myself. I do enjoy the ability to have a larger boat with the fuel economy of a smaller boat. Glass boats are heavier than aluminium boats so the glass boats will use more fuel than alum boats if fuel consumption is that critical to you.

Airshot

 

[Mason78]

Re: O/b vs I/b all things equal

I knew this was going to get way more complex than I had intended! lol

So, lets muddy it up some more! Im looking at a 1999 glastron 190, with a 4.3 merc. as well as a 2001 larson with a merc 150 2 stroke.

Same day on the water, playing cruising etc, which will cost more to run?

I would purchase the boat that is in better condition. The difference in fuel costs should not be that significant between the two.

The real cost will be ; insurance, registration, life jackets, tubes, skis, wakeboards, and ramp fees

 

[HT32BSX115]

Re: O/b vs I/b all things equal

One issue with used I/O is the cost of repairs/rebuilding the drive unit. I have seen boats of similar age to what you are considering that needed a complete overhaul of the drive. I know you didn't ask about that, but since you are concerned with operating costs, repairs must be considered.

My last boat (1966 Marktwain) went 39 years without having to "overhaul" the engine OR drive, and had a 150 HP Mercruiser engine that burned no more than a similar boat with a 150 HP (4-stroke) outboard engine. When it was new, 4-cycle outboards were not common so (back then) it was quite a bit more fuel efficient than a comparable (2-stroke) 150 hp outboard powered boat of similar size.

Fuel cost is usually the tip of the iceberg when owning a boat.

Hmm. well, yeah, if you don't run the engine much, it could be the "tip"...........

But, if you are into skiing or other water sports, running around at some sort of cruising speed a LOT, (and burning 5-7 gallons per hour @ $4/gallon.......)

1000 hours of operation could cost you could cost you up to $20,000-28000 !!. I would call that the WHOLE "iceburg"......not just the "tip"

......Just a reality check.......

Cheers,


Rick

 

[JoLin]

Re: O/b vs I/b all things equal

Hmm. well, yeah, if you don't run the engine much, it could be the "tip"...........

But, if you are into skiing or other water sports, running around at some sort of cruising speed a LOT, (and burning 5-7 gallons per hour @ $4/gallon.......)

1000 hours of operation could cost you could cost you up to $20,000-28000 !!. I would call that the WHOLE "iceburg"......not just the "tip"

......Just a reality check.......

Cheers,
Rick

Different dynamic. Year-round storage, maintenance, repairs, insurance and incidentals far outweigh what I spend on fuel in a season. Your 'reality check' example is 1000 hours run time for a pleasure boater. Yeah, okay.

My .02

 

[QC]

Re: O/b vs I/b all things equal

Somebody needs to prepare an Iceberg graph with all of the costs filled in.

 

[HT32BSX115]

Re: O/b vs I/b all things equal

We are talking about pleasure use aren't we? I would say that someone that uses their boat all summer for recreational use might easily do 100 hrs or so. many go it less, some a little more.


Also, since we're on a DIY maintenance site, where we encourage most people to do their own winterization and a LOT of people have their own storage or park it in the back yard, insurance may only be liability insurance, and if it's a 15-20 year old boat to start with, state registration is inexpensive.

I pay $140/year for (liability) insurance, $25/year for hull registration (+ $22 trailer)

My engine oil change costs about $26 (for 8qts of xxx oil) + $6 for a yyy filter + $36 for zzz synthetic drive oil.

A Bravo raw water pump impeller is $20 (maybe once every 2-3 years) outboard raw pumps are not much more or less.....

The above costs will be the same if you have a similar outboard motor if you do the same things (except maybe a little less oil for the same oil changes)

My fuel tank holds 44 gallons. If I fill the tank only ONCE in the in the summer, (@$5/gallon) it's over $200! how many people only fill their tank once in a summer of use?

Your 'reality check' example is 1000 hours run time for a pleasure boater. Yeah, okay.

10 years at 100 hrs a year sounds reasonable to me.....


Yeah. 1000 hrs for most people over the life of the boat might be very typical (maybe low) .

My "example" boat had the hr meter fail in the mid 80's at 1500+ hours. and that use was from about 1966 to about 1980....... I got the boat in 1997 and used it every year until 2006 when I sold it. All I did to it was replace the raw water pump and coupler (and that because it was probably never lubed).
(I hope you didn't think I meant in 1000 hrs a year) Back when dad bought the boat, gas was $0.35 per gallon. I would've called that the "tip" of the cost "iceburg" back then...........

My whole point here is that the costs are going to be similar for either an outboard boat or similarly powered I/O boat.

For example, my own current (300 Prop HP Mercruiser 7.4L Bravo III) compares closely to a similar sized boat powered with a 300hp Evinrude ETEC

From: Evinrude E-TEC 300 H.P. Outboard 2010 Engine Test / Reviews Videos, Specs, Fast Facts, Captain reports | BoatTEST.com

Performance Numbers

We had the E-TEC 300-hp mounted to the stern of a Dusky 233, and while this isn?t a boat report, the combination was impressive. Test weight was just over 4600 lbs. (2086 kgs.), and top speed came in at 5650 rpm and a respectable 51.7 MPH. That gave us a fuel burn of 26.2 gph and 1.97mpg. Dialed back to a more reserved pace, 3500 rpm showed a best cruise of 28.8 MPH, a fuel burn of 9.3 gph, and 3.11 mpg.

I have a fuel flow indicator on my carbureted engine and at 30 mph, I burn 10 gallons per hour (3.0 mpg) with my evil BBC!
(It sounds FAR COOLER THAN some whiny outboard!!)

I think someone else said it earlier, if you have a planing hull at a given weight, it's going to take APPROX the same amount of fuel per mile to push that thing through the water at a given speed REGARDLESS OF THE ENGINE UNDER THE HOOD OR HANGING OFF THE BACK......... It's just simple physics. (or thermodynamics)


Cheers,


Rick

 

[brnschoneck]

Re: O/b vs I/b all things equal

y i would buy the outboard a lot easier to care for and to me better performance i sold my i/o just to get a outboard...and u have costs both ways even winterizing is cheaper with ob mine takes less lu oil as well a lot less ...idk im just much happier with a outboard just my 2 cents ...

 

[HT32BSX115]

Re: O/b vs I/b all things equal

I read the above article a little further and they compared the ETEC to a "Brand-X" 4-stroke bolted on the back of the same boat.......

At the all-important "Best Cruise" we clocked the Dusky 233 powered by the Evinrude 300 at 3500 rpm going 28.8 mph, getting 3.11 mpg. The 4-stroke 300-hp engine reportedly went 24.45 mph at 3500 (which was also its "Best Cruise") and got 3.15 mpg -- 4.35 mph slower getting 0.04 mpg more. As we said, these numbers are breathtakingly similar.

It appears that the 4-stroke would burn a little more fuel per hour at the same speed......

Now the above "stuff" is probably a tad off-topic.... I don't really think I would necessarily want an outboard boat. but if I was going to get one, and buy it new, I would want it with an ETEC.

Back to the topic.......

Ok, I know this is tough question, but I'm going to ask anyways! All things being equal, same boat, same load, same water conditions, same prop, etc etc... How do the fuel consumption compare with say a 150hp o/b vs a 4.3 I/b?
Thanks

It's not a "tough" question at all!

"All things being equal", I.E the boat, all-up weight and approx prop HP,

The fuel consumption DIFFERENCE will NOT be significant.

 

[JoLin]

Re: O/b vs I/b all things equal

We are talking about pleasure use aren't we? I would say that someone that uses their boat all summer for recreational use might easily do 100 hrs or so. many go it less, some a little more.


Also, since we're on a DIY maintenance site, where we encourage most people to do their own winterization and a LOT of people have their own storage or park it in the back yard, insurance may only be liability insurance, and if it's a 15-20 year old boat to start with, state registration is inexpensive.

I pay $140/year for (liability) insurance, $25/year for hull registration (+ $22 trailer)

My engine oil change costs about $26 (for 8qts of xxx oil) + $6 for a yyy filter + $36 for zzz synthetic drive oil.

A Bravo raw water pump impeller is $20 (maybe once every 2-3 years) outboard raw pumps are not much more or less.....

The above costs will be the same if you have a similar outboard motor if you do the same things (except maybe a little less oil for the same oil changes)

My fuel tank holds 44 gallons. If I fill the tank only ONCE in the in the summer, (@$5/gallon) it's over $200! how many people only fill their tank once in a summer of use?



10 years at 100 hrs a year sounds reasonable to me.....

I was talking about 'per season' ownership cost, not the cost of fuel over the life of the boat. You're also assuming minimal ancillary cost- routine maintenance, no storage cost, no repair cost, no electronics or equipment purchases or upgrades, etc. Heck, if I leave out every other expense and talk only about fuel... then yeah, it's 100% of my boating expense.

As I said before, it's a different dynamic. Where you claim a LOT of boaters have minimal costs aside from fuel, I say a LOT of boaters have substantial costs aside from fuel. It depends on where you live, what kind of boat you're running and where you can keep it. So, where I originally said that 'fuel cost is usually the tip of the iceberg', I stand by that comment. Might not be the case for you, but it is for many.

 

[QC]

Re: O/b vs I/b all things equal

What I will say, is that no matter how you slice it. Even a 10% fuel savings, which would be significant, is insignificant in the grand scheme. Buy the boat that fits your family best and get on the water!!!

 

[HT32BSX115]

Re: O/b vs I/b all things equal

Where you claim a LOT of boaters have minimal costs aside from fuel, I say a LOT of boaters have substantial costs aside from fuel. It depends on where you live, what kind of boat you're running and where you can keep it. So, where I originally said that 'fuel cost is usually the tip of the iceberg', I stand by that comment. Might not be the case for you, but it is for many.

I acknowledge that, but the costs you're mentioning ARE independent of the engine and drive FUEL COSTS, (which is what the OP really wanted to compare) Those other costs you mention would be largely the same for any boat. [give or take]

Fuel costs are much larger than they used to be. And the more you use your boat, they of course become far more significant.

//////////

As an aside, for the OB guys, AND the people that think a V-8 "ALWAYS uses" more fuel than a smaller (displacement) engine,

I took examples from Mercury Marine's website. comparing 2 boats that weigh the same. (4400lbs) one boat had a 200hp Merc Verado OB and the other had a 350 MAG MPI V-8 + Bravo III

The 4400lb boat with the 200hp 4-stroke outboard required 9.4gallons per hour to go 26.5 mph

Engine Test | Mercury Marine

The other 4400lb boat equipped with a 5.7L V-8 and Bravo III required 7 gallons per hour to go 27.4 MPH

Engine Test | Mercury Marine

The I/O used LESS fuel at just about every speed! with a 5.7L engine! (More than 3 TIMES the displacement of the smaller 1.7L outboard!!)


Yes I know it isn't EXACTLY apples to apples but it is burning fuel to push 2 boats (same weight) approx the same speed with a gasoline engine/drive ....... one just happens to be more efficient than the other......

I hope this "puts to bed" the misnomer that bigger engines ALWAYS use more fuel.......

 

[ssobol]

Re: O/b vs I/b all things equal

An outboard motor gets the motor outside of the boat. The space usually taken up by the motors, covers, and some of the bilges can be used for people space. This can be a significant amount of space. Point outboard.

Today's outboard motor is a high tech piece of equipment that is crammed into the smallest possible package. This requires specialized parts, tools, and can make other than basic servicing of the motor a real PITA. Point inboard.

An inboard gas engine is basically a car engine with a very few modifications to the basic engine itself. This can make parts cheaper and more readily available. Point inboard.

As mentioned above styling of the boat is better with an inboard engine. Point inboard.

If your engine breaks down while on the water it is generally easier to fool around with an inboard engine than an outboard in hopes of getting to run again. You don't have to worry as much about tools falling in the water. Point inboard.

If you do have to have major engine work or replace the engine, with an outboard you can replace the whole power train in a couple of hours (if you go slowly). Replacing an inboard is much more involved. Point outboard.

That all being said, I'll take an outboard any day of the week.

 

[HT32BSX115]

Re: O/b vs I/b all things equal

y i would buy the outboard a lot easier to care for and to me better performance i sold my i/o just to get a outboard...and u have costs both ways even winterizing is cheaper with ob mine takes less lu oil as well a lot less ...idk im just much happier with a outboard just my 2 cents ...

Well lets use my example above, shall we?

Lets say you're a "Fishing Fool"! AND the KIDS are Skiers!

You have a favorite fishing "hole" that is precisly 27 miles away. So, it takes you an hour to get there and an hour to get back in those boats above. running that "optimum cruising speed around 27 mph...

You go every weekend during summer. (14 times this Summer JUN-AUG)

That would be 14 times 2x7gal (out and back)................. 28 hours (x7) for a total of 196 gallons With the I/O boat above.

Let also say that the other day of the weekend the kids want to ski (at approx 27 mph for the sake of argument) for a 3-4 hours AND for the same sake of argument you end up with a total of 2 hours of average running at 27mph..... (For another 196 gallons) (that's 392 gallons total for you math wizards!)

AND a total of only 56 hours of average running time for the entire summer.

With the other one running the 200hp OB, the same running would require 56 x 9.4 g/hr or 526 gallons.

At $5/gallon, you're spending (I/O) $1960.00 and (OB) $2630

For the same math challenged ones, THAT'S $670! MORE with the outboard!

If you operate 100hrs, then it's approx $3500 vs $4700 (or roughly $1200) MORE per year.



I don't know about anyone else but I'll take the little bit additional maintenance cost of the I/O.

Besides, the kids wouldn't want to ski behind a 4400lb boat with a 200hp outboard on the back because it would be a REAL DOG out of the hole!

ymmv......


Rick

EDIT: I wanted to look a tad further since some people don't just run at the most efficient cruising speed all the time..........


Just looking at running those same boats at APPROX 38MPH (NOT WOT)

The I/O boat above fuel flow went to 12.8 Gal/hr

and the OB boat went to 16.7 Gal/hr !

and at WOT, The 1.7L 200hp OB burned 38.4 galhr

and the 5.7L V-8 300hp Bravo III I/O burned 25 gal/hr

What were those advantages of an OB again?

 

[QC]

Re: O/b vs I/b all things equal

OK, I went through your math, Rick. Looked at the tests and the hulls, and I have to say they seem fairly valid. On the hulls I was pretty concerned about deadrise comparison, as a higher deadrise will eat more fuel. The fact is, the I/O was 22 degrees, and the O/B Whaler is 21. Conclusion being that the Whaler didn't suffer any simple penalty to explain the high fuel use in the comparison. The rest of the comparison between boats and power seems pretty valid as they reach similar top speeds.

I would say that's a fair comparison, and indeed a 200 hp OB vs. a 300 hp I/O which shows that you can do the same job with a smaller OB, but it won't always burn the same fuel.

With that said, what I do when I make these comparisons is I try any find data that contradicts my belief. If I find 10 examples that confirm my belief and 3 that refute it, I feel much better. Obviously 100 examples that confirm it vs. zero refuting is even better, but I think you get my point. Off to the data mines

 

[QC]

Re: O/b vs I/b all things equal

Here is an interesting pair. "Same" hull:

Bayliner*170 OB (2012-)*2012* Reviews,performance,compare,price,warranty, specs,Reports,Specifications Layout, video | BoatTEST.com

Bayliner*175 Bowrider (2011-)*2011* Reviews,performance,compare,price,warranty, specs,Reports,Specifications Layout, video | BoatTEST.com

1st one is a 115 Mercury (I think four stroke, but oddly missing . . .), Second one a 135 Merc Alpha I/O. Top speed favors the I/O, fuel economy favors the OB. Same hull, but I/O 500 lbs heavier.

 

[HT32BSX115]

Re: O/b vs I/b all things equal

Best cruise for the Bayliner 170 OB (2012-) is 20.6 mph (33.2 kph), and the boat gets 6.74 miles per gallon (mpg) or 2.87 kilometers per liter (kpl), giving the boat a cruising range of 127 miles (204.39 kilometers).

the venerable 135-hp MerCruiser 3.0L. You can get power steering or a catalytic converter, but it’s still the 3.0L. We found the top speed to be a respectable 44.1 mph while burning 11 gph. Our best cruise came at 3000 rpm and 24.4 mph while burning only 4.6 gph.

~5.3mpg

The lighter weight of the OB appears more significant in a smaller boat. It might be that a 300HP OB might compare more favourably with a 300hp I/O in a similarly sized boat.....