Fuel economy - inboard vs outboard

[DuroBoat]

I’m a bit confused and I know this site has tones of real world experience….

I’m podding my 22’boat and replacing the 5.7 Volvo Penta with a new 300hp yammy. I was getting increadable fuel economy from the inboard 5.7 and am expecting comparable economy from the new Yamaha but my mechanic thinks I’ll be burning 2 - 3 times the fuel with the new outboard. Is this right??

 

[noluck]

I’m a bit confused and I know this site has tones of real world experience….

I’m podding my 22’boat and replacing the 5.7 Volvo Penta with a new 300hp yammy. I was getting increadable fuel economy from the inboard 5.7 and am expecting comparable economy from the new Yamaha but my mechanic thinks I’ll be burning 2 - 3 times the fuel with the new outboard. Is this right??

good chance you will burn more fuel

 

[Fishtank]

He's probley just saying that cause he's pissed that he won't be seeing you for a real long time time!

 

[Brando]

What’s “incredible” fuel economy. Need some numbers or it’s all just guessing

 

[scott craven]

Do you need a 300hp ?
22' should be fine with a 225 or 250 ?

 

[DuroBoat]

What’s “incredible” fuel economy. Need some numbers or it’s all just guessing

I’ll admit I didn’t analyze numbers (for example, a 4-day camping trip with a family of 4 leaving from Nanaimo to circling Bowen island then to chemainus and back to Nanaimo used just over 1/2 my 100 gal tank). Seemed pretty good to me.. Will a similarly sized new outboard use substantially more than an inboard, all else being the same?

 

[DuroBoat]

Do you need a 300hp ?
22' should be fine with a 225 or 250 ?

Ya, but they are all the same weight.. an extra $2k now and I know I won’t regret it down the road. A lot of gear can fit on a 22’ so the more hp the better (within reason guys). Plus, it was difficult to find any 250 - 300 outboard anywhere now. I had to put a deposit down to ensure it will still be there when the pod is done. … and the best reason to go 300 is because it will look badass hanging off the stern

 

[Captain PartyMarty]

Higher Horse Power means lower cruising RPM which should bring down your fuel bill assuming its the same weight. Your fuel will definitely go up. 2 to 3 times is a bit out to lunch.

 

[Brando]

Your pod design will factor into the fuel economy as well, I don’t think your going to substantially increase your fuel burn it should be reasonably close to the same depending on prop selection/motor height and pod design, consider the weight savings as well and I think your going to balance out pretty well..

Sounds like your trip used around 200L that’s pretty decent, you could chart it and get a rough idea of mileage…

 

[Rain City]

Everyone seems to say 2-3 times to me as well but I just can't seem to believe that for a second.

 

[Brando]

Everyone seems to say 2-3 times to me as well but I just can't seem to believe that for a second.

Diesel to outboard maybe, gas to outboard… wouldn’t believe that either.

 

[seabeyond]

Everyone seems to say 2-3 times to me as well but I just can't seem to believe that for a second.

Rain City, I don't know that your situation is not particularly relevant to this thread. Duroboat is replacing a 5.7 gas, your talking diesel....

My main comment would be if you don't know your mpg numbers I don't know how you could accurately tell if the mileage is better or worse. There's to many variables on a multi day trip that change day to day.

Your going to spend a small fortune podding the boat. Unless you put a couple hundred hours a year running at speed on your mains, who cares about 10% +/- on your old burn numbers. If it's better which I'd hope it would be, great.

I'd pod the right 22 ft boat for reliability, less maintenance costs and to get rid of the dog house. I couldn't see a way a modern 300 yam would be much worse than a 5.7. I could see it being better.

Put your efforts into making sure the pod is done right.

 

[DuroBoat]

Higher Horse Power means lower cruising RPM which should bring down your fuel bill assuming its the same weight. Your fuel will definitely go up. 2 to 3 times is a bit out to lunch.

..whew, I was starting to get concerned lol

Your pod design will factor into the fuel economy as well, I don’t think your going to substantially increase your fuel burn it should be reasonably close to the same depending on prop selection/motor height and pod design, consider the weight savings as well and I think your going to balance out pretty well..

Sounds like your trip used around 200L that’s pretty decent, you could chart it and get a rough idea of mileage…

Thanks Brando - I really should have plotted it and gotten my real inboard numbers to compare to the outboard but really, at this stage, it should be all about smiles per gallon, not mpg . Battery and controls getting pulled this afternoon so it’s go time. The next time I take her out there will be a big outboard hanging off the back and a big hole in my bank account

 

[ab1752]

Everyone seems to say 2-3 times to me as well but I just can't seem to believe that for a second.

That's because they know you only have 2 throttle settings; idle and fast af

 

[ab1752]

..whew, I was starting to get concerned lol

Thanks Brando - I really should have plotted it and gotten my real inboard numbers to compare to the outboard but really, at this stage, it should be all about smiles per gallon, not mpg . Battery and controls getting pulled this afternoon so it’s go time. The next time I take her out there will be a big outboard hanging off the back and a big hole in my bank account

Any details on your pod you can share? Are they doing it out of glass or tin?

 

[DuroBoat]

Any details on your pod you can share? Are they doing it out of glass or tin?

I’m using Jenkins in Sooke as they have done a few seasport pods recently and they do quality work. Aluminum powder coated white, full hull extension and getting the doghouse removed. I’ll post a few pics once some work has been completed. Like most of us, this process is completely new to me so I’ve just started removing the old gauges and electrical wiring today and figuring it out as I go. Except for the fuel gauge, I’m guessing this entries mess has to go. Jenkins and SG Power will do all the really hard work

 

[MRWood]

I’m using Jenkins in Sooke as they have done a few seasport pods recently and they do quality work. Aluminum powder coated white, full hull extension and getting the doghouse removed. I’ll post a few pics once some work has been completed. Like most of us, this process is completely new to me so I’ve just started removing the old gauges and electrical wiring today and figuring it out as I go. Except for the fuel gauge, I’m guessing this entries mess has to go. Jenkins and SG Power will do all the really hard work

You didn't say it was a 22' Seasport you were podding. That will be awesome. I'd love to upgrade my 19' Seasport to a 22' with a pod. Your boat looks great.
I assume your 5.7L would be 250HP while your outboard is 300HP so that right there will be a bigger fuel burn. In order to analyze it properly you'd need to know your gallon per hour burn at say 25 knots and then compare to the 300HP. I don't think there is any way it would be 2-3 times the burn rate.

 

[Rain City]

I’m using Jenkins in Sooke as they have done a few seasport pods recently and they do quality work. Aluminum powder coated white, full hull extension and getting the doghouse removed. I’ll post a few pics once some work has been completed. Like most of us, this process is completely new to me so I’ve just started removing the old gauges and electrical wiring today and figuring it out as I go. Except for the fuel gauge, I’m guessing this entries mess has to go. Jenkins and SG Power will do all the really hard work

Nice boat

 

[DuroBoat]

You didn't say it was a 22' Seasport you were podding. That will be awesome. I'd love to upgrade my 19' Seasport to a 22' with a pod. Your boat looks great.
I assume your 5.7L would be 250HP while your outboard is 300HP so that right there will be a bigger fuel burn. In order to analyze it properly you'd need to know your gallon per hour burn at say 25 knots and then compare to the 300HP. I don't think there is any way it would be 2-3 times the burn rate.

You didn't say it was a 22' Seasport you were podding. That will be awesome. I'd love to upgrade my 19' Seasport to a 22' with a pod. Your boat looks great.
I assume your 5.7L would be 250HP while your outboard is 300HP so that right there will be a bigger fuel burn. In order to analyze it properly you'd need to know your gallon per hour burn at say 25 knots and then compare to the 300HP. I don't think there is any way it would be 2-3 times the burn rate.

I understand the Volvo 5.7 Gi is rated at 300hp and likely has a lot more torque than a 300 outboard so any performance differences should be interesting. The outboard does shave off 500 lbs from the inboard which is significant on a 22’ boat

 

[MRWood]

I understand the Volvo 5.7 Gi is rated at 300hp and likely has a lot more torque than a 300 outboard so any performance differences should be interesting. The outboard does shave off 500 lbs from the inboard which is significant on a 22’ boat

You're correct to go with the 300HP then. 500lbs, that's like losing a couple tubby fishing buddies, that will make a difference. Good luck would like to see it finished. Do you live in Nanaimo?