Carburated vs. Fuel Injected

[SeaDooSam]

I have a theoretical question. If I were to have two of the same boats and one had a carburated engine and one had fuel injection, If they had the same horsepower, would one perform differently? Would the carburated be faster or slower than the other as far as top end speed?

Thanks!

 

[Bondo]

Ayuh,..... If ya had 2 identical 350s, 'n 1 with a Merc/ Weber 4bbl. carb, 'n the other a throttle body Efi,....

The only difference is not needin' to advance the throttle to Wot on a cold motor to set the choke, on the Efi motor,..........

 

[SeaDooSam]

OK so it should be the same. that is what I thought

 

[alldodge]

Agree but with one comment: this has been discussed many times on OSO. They find that with high performance boats there is a slight bit more HP being produced at WOT with a carb over EFI.

 

[thumpar]

If it was MPI there would be a difference but carb vs EFI is not going to be noticeable HP wise. You will notice better starting and maybe some throttle response from the EFI but the throttle response would only be when the carb is worn. Personally I like the EFI but there is nothing wrong with a carb.

 

[JoLin]

I've had both.

1997 Four Winns 27' with twin Volvo throttle-body injected 4.3's. NOT a duo-prop.

1992 Carver 26 Flybridge with twin Merc carbed (4 barrel) 4.3's.

In some respects I'm comparing apples to oranges, but I think that the major differences between the two boats kinda even out, i.e., the Carver is 1,000 lbs heavier than the Four Winns, but has less deadrise. 15 degrees vs.18 for the FW.

Starting was a little easier with EFI. Performance 'out of the hole' is similar. The Four Winns could run up to 36-37 mph. The Carver has hit 39+. The big difference is in economy. I never had a fuel flow meter, but over a couple of seasons of similar use the Four Winns averaged 1.6 mpg, where the Carver does 1.2.

A boat with MPI would likely do better than either of them.

My .02

 

[jimmbo]

I know when EFI was being introduced(early 2000s) engine were often available with either. I'm using Volvo examples here, but merc was similar back then. A carbed 305 had 220hp a FI had 260hp. A carbed 350 was 260hp while a fuelie was around 300. The carbed engines were rated at 4600 rpm and the fuelies were 5000 rpm. While the 305 FI and the 350 2bbl carbed were both rated at 260 they sure didn't perform the same.
I did have the opportunity to compare my boat, with carb 350, to the same boat with a 305 FI. The 350, with more torque, had much better holeshot and would run away from the 305. I don't think the 305 ever attained the same top speed as be, but that may have been aluminium prop vs SS.
The carbed 350 could always gain hp with a 4bbl carb as the 2bbl(500cfm) was a little small for a 350 turning 5000 rpm. The Holley 2bbl(500cfm) was just about perfect for a 305 turning 5000 so going to a 4bbl wasn't going to give much of an increase in hp.

 

[thumpar]

I know when EFI was being introduced(early 2000s) engine were often available with either. I'm using Volvo examples here, but merc was similar back then. A carbed 305 had 220hp a FI had 260hp. A carbed 350 was 260hp while a fuelie was around 300. The carbed engines were rated at 4600 rpm and the fuelies were 5000 rpm. While the 305 FI and the 350 2bbl carbed were both rated at 260 they sure didn't perform the same.
I did have the opportunity to compare my boat, with carb 350, to the same boat with a 305 FI. The 350, with more torque, had much better holeshot and would run away from the 305. I don't think the 305 ever attained the same top speed as be, but that may have been aluminium prop vs SS.
The carbed 350 could always gain hp with a 4bbl carb as the 2bbl(500cfm) was a little small for a 350 turning 5000 rpm. The Holley 2bbl(500cfm) was just about perfect for a 305 turning 5000 so going to a 4bbl wasn't going to give much of an increase in hp.

He was asking about EFI vs carb with the same HP. My 1996 is EFI so it was before 2000's that EFI came out. My engine makes the same HP as the equivalent carb motor.

 

[jimmbo]

I know what he asked. However they were never marketed as Identical HP. So it has always been apples to oranges comparisons. In theory, there should be no difference but in the real world...

 

[thumpar]

I know what he asked. However they were never marketed as Identical HP. So it has always been apples to oranges comparisons. In theory, there should be no difference but in the real world...

They were marketed as the same HP.

 

[Scott Danforth]

the Four Winns averaged 1.6 mpg, where the Carver does 1.2.

A boat with MPI would likely do better than either of them.

My .02

A properly tuned carb and efi should get the same fuel economy. A naturally aspirated SI motor should burn approximately 0.40# of fuel per hp-hr. EFI gets you easy starting and ability to self adjust for barometric pressure