questions on carb vs fuel injected boat engines

All right, here’s the deal. The last two engines I’ve had have been the same: they are both Mercury 115 ELPTOs, which are carb engines that have the 2+2 feature. Meaning, when you’re going under 1800 rpms, you’re only using 2 cylinders. After that, they all 4 kick in. Fishing the King Kat Classic down in KS, I’m noticing we’re using a lot of gas. Maybe it’s time I get serious about learning about the fuel injected motors out there. I’ve never had one but need to find out more about them.

So here are the questions. If I were to step up to a v6 fuel injected engine, how much fuel would I save? I fish a lot of 5mph water around here, so that’s when only using 2 cylinders is nice. If I’m using all 6 but only going 5mph, am I still going to burn quite a bit of gas?

Also, what motors are better, your guys’ opinion? The reason I ask that question is becuase I’m hoping I’ll get quite a few responses. I’m (possibly) looking at an older (’00) Yamaha HPDI. What do you guys think of different motors, including this one? Can you compare some?

Also, I do have the Lowrance network on my boat, and have added the fuel usage sensor. It pops right up on your finder’s screen and tells you how many GPH, MPG, and different stuff like that. Anyone use one of these and can give me readings? I know when I’m only using 2 cylinders, I’m using about 2.0 gallons per hour (GPH) at that setting. When I crank it up and am going full bore, I’m using about 12.5-13.0 GPH, but that’s at wide open. I can tune it into 7.0-9.0 GPH if I want to, which is nice.

I’m really looking forward to hearing what you guys have to say. Thanks for your time.

It wont be long and almost everything will be fuel injected.You can check out this site http://www.yamaha-motor.com/outboard/products/lifestylehome/home.aspx and click on performance bulletins to get a good idea on what mileage these engines get.

Let’s see, who was it that just posted that terrible nasty joke about the Vikes recent loss???? Now you’re expecting these same poor hapless Viking fans to bail you out. GO BIG RED – – -jerr

Brian my 150 horse opti max is just a 4 cylinder but the gauges show the trolling or under 5 mph usage at under a gallon per hour.We were trolling about 2.5 mph the other day with fuel usage at .4gph my top end usage is running me around the 13 gph though rapped out.

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Brian my 150 horse opti max is just a 4 cylinder

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sharkbait, you need to pull the cover off that motor and count the spark plugs! Pretty sure all of the 150 optis are 6 bangers….

-J.

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If I were to step up to a v6 fuel injected engine, how much fuel would I save?

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Depends. If you kept the RPMs 4000 or lower, quite a bit. Run WOT all the time and you will use a lot of gas for the miles covered. One thing for sure, you will save a ton on oil payments…

-J.

Thanks for that reminder, Jerr!!

Thanks guys for the info, especially that link, Castaway. That’s pretty helpful. I’ve been told quite a few times that the oil consumption will really go down, so that’s good. I don’t feel like I use a lot now, so using less would rock.

Here’s the deal….the boat I’m looking at is about the same as mine, not really longer, and maybe an inch narrower. But it’s got a 150 VMax on it, and I fish a lot of 5mph waters. I don’t like to use the kicker that much for getting around the lake, but being a 15hp, maybe I could.
Looking at those performance charts on that site, they look real comparable to my 115. But when you look at the engines that are fuel injected, you CAN see a difference. Thanks, that helps a lot.
Brian

Take a closer look at the motor. Not all VMAX motors are fuel injected. Mine (2003) is a carb motor. They also made the OX66 (fuel injected) and the HPDI (Direct Injected).

3 different technologies. Of the 3, the HPDI is the most fuel efficient, with the OX66 second and carb third.

At WOT, they all burn about the same amount of fuel, but at mid and low range is where the fuel injected and direct injected shine. The added advantage of fuel or direct injected is startability. A carb motor is harder to start, where the other two should pop off instantly if kept tuned.

As mentioned, the FI and DI motors will use less oil.

The flip side to all of this is the carb motors are pretty much bullet-proof and cheaper to work on.

Glenn

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Brian my 150 horse opti max is just a 4 cylinder

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sharkbait, you need to pull the cover off that motor and count the spark plugs! Pretty sure all of the 150 optis are 6 bangers….

-J.

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It is indeed a 6.

On balance I think the injected motors are better.Not because of economy but because of performance.Not go fast performance,but start in all stages of engine temp,all stages of ambient temp etc.
Any engine requires a specific fuel/air mix,regardless of the mechanism which provides it.The carb engines rely on jets which can not change.Frequently they will be either rich or lean (fuel air ratio) at some portion of the RPM range,temp range etc.
Injected motors rely on censors or maps(computor programs) to control the fuel/air ratio.The amount of fuel is varied greatly reducing the rich or lean conditions which is more prevelent in carbed engines.

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////////////////////////So here are the questions. If I were to step up to a v6 fuel injected engine, how much fuel would I save?”

In my opinion going from a four to a six cylinder engine you will use MORE fuel.A better comparison would be a six carbuerated vs a six injected.

“Also, what motors are better,”

In my humble opinion,the Honda four strokes are top of the heap…but SPENDY.(I own a Yamaha,carbed)

Thanks guys, I do appreciate those answers. I will look closely at the Yammy in about 8 hrs to see exactly what model it is (I have my doubts about it being an HPDI, so it’s probably the level below). We’ll see what shakes out.

Skunked is about right. The fuel injected motors are so much better, albeit do not discount the E-TEC. My 90Hp acually starts immediately and always has. Nonetheless, my personal suggestion is avoid the carb motors.

I really do like when I turn the key my motor starts, no questions asked only once did I ever have to turn to key twice to start my motor, and it had been sitting for a couple months and it was 14 degrees, so I’ll let it slide.

I think skunked it pretty right on, (though I can’t say Honda is the best, I can’t say they aren’t.)

I run a 200 Yamaha ox66 fuel injected (non HPDI) I wouldn’t reccomend it for gas mileage, but it preforms well