I/O vs. Outboard Fuel Consumption

[NHGuy]

Re: I/O vs. Outboard Fuel Consumption

Cyclops hit it right on the head. In a boat or your cool Saturday night cruise car you are looking for smiles per gallon.

ps. Happy Holidays & Merry Xmas

 

[dingbat]

Re: I/O vs. Outboard Fuel Consumption

Fuel is the cheap part of boating. If you're worried about the fuel cost, you better look for a different hobby

 

[cyclops2]

Re: I/O vs. Outboard Fuel Consumption

Ding bat has me pegged.

I use MAYBE 40 to 50 gallons of regular a year in the Chaparral SSI 5.0 L.
The 16' Lowe with a 9.9 hp & electric start. 8 gallons a week. May 10 thru September 15. Weather permitting. No typing error.

 

[smokeonthewater]

Re: I/O vs. Outboard Fuel Consumption

Fuel is the cheap part of boating. If you're worried about the fuel cost, you better look for a different hobby

Strange... fuel has always been the single biggest cost for me...... from my first 12' tinny 25 years ago to my 30' cruiser now, fuel has always been the one thing that hurts the wallet more than anything else.

With my current boat, if I just ease out to the island that I can see from the ramp, and spend the day before easing back, it still costs me $50 and if I pull tubes it's $200- $500...... I pretty much never pull tubes.

 

[Home Cookin']

Re: I/O vs. Outboard Fuel Consumption

Another thing, the discussion always centers on fuel/speed/distance/engine performance at WOT. That maybe what lake boaters do all day, but not open water boaters, especially not larger ones (because you are on bigger water; the 12' jon/9.9 will usually be run at top end).
Just like cars, there is a fuel efficiency at lower speeds. but there is also the GPH factor where going too slow (car or boat) will burn more fuel for the miles than going faster. For small cars that speed is about 48 mph I read somewhere.

So a recreational boater on a WOT lake may use more fuel per outing than one with basically the same boat on the bay.

Even when it's flat I don't usually run WOT; the motor is loud and I feel like it's working too hard (tach says it's not). An OB has a sweet spot where the motor sounds good and pushes you along smooth quick adn quiet. Cars are like that, too.

I'm not smart enough to figure out if my 150 HP running at 3/4 throttle for 30 mph uses the same fuel as a 115 at WOT at 30 mph. That's not what I have a boat for; it's what I have a boat to get away from.

 

[Cherokee-Runabout]

Re: I/O vs. Outboard Fuel Consumption

Boats and fuel economy? :lol: :lol: :lol:


You're kidding right?

It's not so much economy as much as efficiency that I was debating, but thanks for the input anyhow.

And no I'm not expecting a 4cyl mericruiser to match that fuel economy that I may receive in say a new Honda Civic.
Sorry I did not elaborate enough. The car analogy apparently caught some of you with one foot off the merry-go-round.
"Fuel is the cheap part of boating. If you're worried about the fuel cost, you better look for a different hobby." Once again, not worried about cost, just trying to be efficient. Trying to have my fun and pull my weight in the environment. Perhaps I ought to take up sailing.


Thank you JoLin, that's basically what I wanted to know.

 

[cyclops2]

Re: I/O vs. Outboard Fuel Consumption

Sailing is greener.

Thank you for leaving me your gasoline to use.

 

[JoLin]

Re: I/O vs. Outboard Fuel Consumption

Strange... fuel has always been the single biggest cost for me...... from my first 12' tinny 25 years ago to my 30' cruiser now, fuel has always been the one thing that hurts the wallet more than anything else.

Smoke, when I owned my 21 and 24 footers, I hauled them home for the winter and serviced them myself. I'd agree that fuel was the a comparatively big cost then, though summer dockage is always expensive here- about $60/foot for the season.

Now, the biggest costs lie in having a place to keep the boat. I can't physically do much of the work myself (especially with twin engines and a cramped ER) and I don't have room in my driveway to keep Escapade there. Summer dockage and winter storage (which includes winterizing all systems, lube and filter changes, shrinkwrap, yard storage and spring commissioning) account for more than half of my annual cost. Then there's insurance, repairs, upgrades... my fuel cost last season (app. 350 gallons) was less than 1/3 the total cost of ownership.

So, every boater's situation is different.

My .02

 

[79Merc80]

Re: I/O vs. Outboard Fuel Consumption

I have a friend that couldn't believe how much fuel my old 90HP Mariner inline 6 used and that it only went 43MPH. She said she had 110hp in her car and it went 75 mph and was good on fuel. My responce to that was "Put your car in second gear and drive it for a week and see how fast you go and how much fuel you use." "Boats don't have the 3, 4, or 5 gears that your car does." "Also, water will stop a boat without power than a car will."

Get your boat up to 40mph and quickly, bring it back to neutral. Then do the same in a car. The car will coast a lot longer than the boat will. There is never a time in a boat where the engine is "Coasting", it's always under a load.

Craig

 

[04fxdwgi]

Re: I/O vs. Outboard Fuel Consumption

Ding bat has me pegged.

I use MAYBE 40 to 50 gallons of regular a year in the Chaparral SSI 5.0 L.

Don't go out much? If running 40 /50 miles up / down river and doing some tubing, I can use 40-50 gallons every time out. LOL

 

[H20Rat]

Re: I/O vs. Outboard Fuel Consumption

I'm not smart enough to figure out if my 150 HP running at 3/4 throttle for 30 mph uses the same fuel as a 115 at WOT at 30 mph. That's not what I have a boat for; it's what I have a boat to get away from.

Those two are probably going to be very, very close in that situation. The 115 is lighter, so depending on the hull, that by itself will help mpg's. But an outboard at WOT is operating in a really inefficient area, so it's wasting a little fuel to stay on the safe side of stoich.

 

[Chris1956]

Re: I/O vs. Outboard Fuel Consumption

Cherokee, As was said, there is no meaningful comparison between marine and auto powerplants. However, a comparison of fuel economy between outboards and I/Os on the same hull is a viable discussion point.

I have had both tyoes of engines on similar (not identical) hulls. I think the following are safe conclusions to draw.

I/O motors will need a bit more HP to perform as well as an outboard, due to their greater mass.
I/O motors will use less fuel (up to 50% less) than a carberator-equipped OB that provides the same WOT performance.
DI Outboards and 4 cycle outboards will use less fuel than a carb- outboard. I have not compared them to I/Os.
Fuel-injected (non-DFI) conventional outboards use about the same fuel as a carb-equiped outboard.
I/O motors require lots more maintenance than outboards. This offsets most/all of the fuel penalty

 

[smokeonthewater]

Re: I/O vs. Outboard Fuel Consumption

Cherokee, As was said, there is no meaningful comparison between marine and auto powerplants. However, a comparison of fuel economy between outboards and I/Os on the same hull is a viable discussion point.

I have had both tyoes of engines on similar (not identical) hulls. I think the following are safe conclusions to draw.

I/O motors will need a bit more HP to perform as well as an outboard, due to their greater mass.
not necessarily, weight distribution makes a difference and 4 stroke3 outbosrds weigh more than 2 strokes.

I/O motors will use less fuel (up to 50% less) than a carberator-equipped OB that provides the same WOT performance.

compared to a 2 stroke, yes but again if both 4 strokes may not be true

DI Outboards and 4 cycle outboards will use less fuel than a carb- outboard. I have not compared them to I/Os.

usually true/very true

Fuel-injected (non-DFI) conventional outboards use about the same fuel as a carb-equiped outboard.
generally agree

I/O motors require lots more maintenance than outboards. This offsets most/all of the fuel penalty


totally untrue
winterizing an i/o is more involved but lots more maintenance... no way.

Just my .02 tho ... opinions on this subject will vary WILDLY and the debate can get VERY aggressive.

 

[coolbri70]

Re: I/O vs. Outboard Fuel Consumption

i use a gas card with a reward program:facepalm:

 

[Chris1956]

Re: I/O vs. Outboard Fuel Consumption

Smoke, When was the last time your outboard needed new U-Joints, bellows, water hoses, manifolds, risers and fan belts? These are standard replacement items for an I/O, in addition to the common replacemnts items that both I/Os and OBs share. In addition, my experience has been that I/O's also require replacement of circulating pumps, alternators, starters, thermostats on a non-regular schedule. Those items just break for some reason....

 

[smokeonthewater]

Re: I/O vs. Outboard Fuel Consumption

Well this is the part where opinions vary.... I've never had to replace a u joint EVER on any boat.... bellows are a 5-10 year item and often neglected for 20 water hoses same manifolds/risers generally 20 years or more (edit maybe much more) unless in salt and salt eats outboards as well. No fan belts on a boat but accy belts last a good long time and on MOST are quick easy and cheap to change. alternators, starters, and thermostats are all found on outboards and just as likely to need servicing on them.... I'll grant that on SOME I/O boats a starter can require pulling the engine but then an alternator on most outboards requires pulling the flywheel.

I've seen PLENTY of 30 plus year old I/O's with most likely the original belts, hoses, bellows, and about everything else still on it... NOT saying that isn't the mark of a LAZY boater but you just can't say that an I/O is LOTS of maintenance... I DID have to replace my starters last july but MY engines were pulled out of a boat that sank in the hudson river and sat for a couple months before I cleaned em up and put em to use ... they looked to be (tho I can't say for sure) the original (1987) starters and I SHOULD have replaced them when I swapped in the engines instead of running them for almost two seasons with water in em.

My outboard on my other boat has corrosion issues causing an external water leak, trim system issue (leaks) It had wiring problems, charging problems and fuel system problems... granted it is 10 years older than the I/O's but I've had other I/O's just as old as it.

 

[Chris1956]

Re: I/O vs. Outboard Fuel Consumption

Smoke, Then you agree there are lots more maintenance parts on an I/O. That was the point. The fact that changing them is not an issue for you, is beside the point. I wanted to give the OP a real idea of the differences between an OB and an I/O, in terms of ownership costs. Manifolds and risers are $700 or more a set, if you do all the work yourself. That averages $70+ per year. U-joints are $50 ea, unless you can match them up at an auto parts place. Belts were $70 a set the last time I went to Mercruiser. Bellows are over $100 a set. In addition, thermostats,alternators, starters and circulating pumps fail in I/Os, whenever is most inconvenent. I am not sure of the reason, but I have experienced it I have had my oil pan rust thru. Same with the timing cover. My OBs need fresh fuel and away we go. In addition, my 150HP OB weighs about 1/4 of what my 4.3V6 Mercruiser did. Just some data points....

 

[smokeonthewater]

Re: I/O vs. Outboard Fuel Consumption

no.... I don't agree.... I know that because I SAID I didn't agree..... Most of the items you mentioned apply to both motors.... the manifolds and risers on my 78 arrowglass cuddy mercruiser 898 (305 chevy) along with the engine with most likely original and at least older than 20 years parts outlasted the boat.... The boat got ONE new set of bellows.... I still have the engine and accys..... other than the bellows (replaced after 25 years of service) the only two things that boat ever got was gas and oil changes. I did buy spare belts for $15 at oreily's but never got around to installing them.

I bought the boat from the original owner around 2002 and he claimed to have never done anything to it other than changing oil and spark plugs.

 

[QC]

Re: I/O vs. Outboard Fuel Consumption

I am kind of with Chris here as what the topic ultimately is is $ per mile, not MPG. However . . . If you use the 10% of rated for OB fuel use which is still apparently valid for both DFI 2 strokes and 4 strokes, you need to recognize that modern I/Os are as good as 6.5 to 8% of rated, so the fuel difference could buy an awful lot of maintenance IF you run a lot . . . Something to consider

 

[smokeonthewater]

Re: I/O vs. Outboard Fuel Consumption

BTW I forgot to add the smiley..... ... no hard feelings here... yep point is dollar for dollar, you just can't rule one out and while there MAY be more maintenance on one than the other it's not a huge difference.