9.9 HP Carb vs. EFI Fuel Economy

[willy13]

I am in the market for a 9.9 HP outboard for a 23 ft sailboat for exploring the Florida keys. I will not be sailing, only putting around at hull speed, 6 mph up and down the keys. So I am interested in fuel economy. Yes, I know, put up the sails...., but my wife and I do not want to learn how to sail... We chose a sail boat hull because of there big cabins. All of the older cabin cruisers are too heavy and wide to tow to Florida.

So given that Mercury has a 9.9 HP with a Carb and with EFI, I was hoping I could get an unbiased answer. I see that Honda and Yamaha are still using carburators on their 9.9 hp, while Tohatsu, Mercury and Suzuki are using EFI. I am aware Mercury rebadges Tohatsu. I expect to be cruising at around 2500 to 3000 rpms. And I read thats where EFI really shines in fuel economy. But if so, why has Honda and Yamaha ignored EFI for there 9.9 HP offerings? Tohatsu claims a 50% increase in fuel economy over there competitors, but its there data, not a 3rd party study.

On a side note, I will also need to charge batteries. They all seem to have stators not alternators, even Honda which claims that they get a full 12 amp output at 3,000 rpms. Correct me if Im wrong on the Honda specs. The Mercury/Tohatsu also has a 12 amp output but I couldn't find the RPM. Not that I need 12 amps of charging.

Thanks for any input,
William

[Boondock]

EFI for sure

Why would you choose carb if you have a choice?
15EFI merc puts out a lot more power to recharge your battery. IIRC less than 1K difference in price and 15lbs

[EuropeanAM]

EFI will have benefits in the form of easier starting, and very slightly less prone to fuel system problems. Overall economy difference will be negligible.

Charging system on that small of an engine is going to be a stator system. They work fine when properly connected to an amply rated LEAD ACID battery.

[bloodman]

After running many many hours on a merc 15 efi, I dont think there is much difference in economy. Ease of start is also debateable.

[willy13]

Well that would explain why Honda and Yamaha did not bother switching to EFI yet. For my situation, it looks like the center mounted tiller handle will be a benefit.

I plan on having 4 group 24 batteries run in parrallel for powering stuff over night. Then slowly recharging through out the day of driving around. Does anyone know what RPM charging kicks in?

[EuropeanAM]

It's present at idle, but very little output. Output increases with engine RPM's.

[JS!]

William, not sure what the lead time is now, but I ordered my 9.9 EFI in December, 2021 and it is finally arriving next week. FYI