Corvette eng fuel use

[Catimann]

36' wood boat from 1952 in great shape that has two 327 corvette motors. Since I am boat stupid, how much fuel would these use? 1) Going slow: 7 knots say. 2) On plane

Would a holly fuel injection unit help?

[thinwater]

Originally Posted by Catimann

36' wood boat from 1952 in great shape that has two 327 corvette motors. Since I am boat stupid, how much fuel would these use? 1) Going slow: 7 knots say. 2) On plane

Would a holly fuel injection unit help?

It's all about how hard they are pushing (cars coast most of the time). Figure about 1 gallon per hour per 10 horsepower used. Depending on the hull form, 7 knots might require 40 hp, or 1.75 mpg. Plane is very boat specific, and many only semi-plane, but figuring 200 hp at 25 knots, about 1.25 mpg. But you would really need to get numbers from a comparable boat.


No, fuel injection won't make a lot of difference. With 70-year old wood, I doubt you are horsepower limited.

[Woodland Hills]

Originally Posted by Catimann

36' wood boat from 1952 in great shape that has two 327 corvette motors. Since I am boat stupid, how much fuel would these use? 1) Going slow: 7 knots say. 2) On plane

Would a holly fuel injection unit help?

If it’s propped correctly and the secondaries don’t open at hull speed it could get OK mileage. Once the secondaries open it will drop exponentially. 327’s are small motors for a boat so you will have to work them hard compared to big blocks.

IMHO, efi won’t help much if the carbs are clean and jetted correctly. Unless you are planning to be on and off of the throttles when cruising these are essentially constant speed motors: you set your cruise rpm, synchronize the motors and leave them there. There is no altitude change like a car climbing a mountain and no accelerating away from a stop all the time either. That and temperature compensation is where an EFI shines compared to a carb. EFI will probably start easier and idle smoother though.

[rsn48]

Let me ask you another way, how deep is your credit card?

[NPCampbell]

Originally Posted by Catimann

36' wood boat from 1952 in great shape that has two 327 corvette motors. Since I am boat stupid, how much fuel would these use? 1) Going slow: 7 knots say. 2) On plane

Would a holly fuel injection unit help?

I was going to install a Holley Sniper EFI on my 350 until I found out it was bored 60 over on the rebuild. From my research on the EFI, starting is rock solid and slow speed metering will be considerably more reliable than carbed. Your unit won't be able to self-learn unless it is operating in closed loop mode with an O2 sensor and MAF and the engine reaches the correct operating temp (at least 160?). With just the self learn, I have read the fuel improvement over a correctly jetted carb is modest around 5-15%.

However, you do have the ability to fine tune the idle, cruise and WOT AFR. Some people have seen upwards of 30-40% fuel efficiency improvement when properly setting the AFR just shy of lean, adjusting the ignition timing parameters, etc.

[mohave_steve]

I have been wondering the same.

I come from a sailing background and am now considering a power boat.

I have seen a couple of Carvers around 31' , 10k displacement and twin engines. One small block chevy (350?) and the other big block (454?).

I don't need to go fast. From my perspective, 6-7kts is fine. It's about the journey, not the destination.

Simple hull speed calc gives me 6.8kts.

If I open the throttles just enough to hold 6kts, how do I estimate the HP needed? With that & SFC I can calculate fuel consumption.

Or..... Somebody with a similar boat could share their fuel #'s???

Thanks.

S.

[deblen]

Great engine!! / Len


https://www.opgi.com/blog/2013/12/the-chevrolet-327/

[thinwater]

Originally Posted by mohave_steve

...Or..... Somebody with a similar boat could share their fuel #'s???

Thanks.

S.

Try the Hull Truth. More of a power boat forum. But with gas and a moboat design, I'm guessing 2-3 mpg. My 34-foot cat, with a much smoother hull form and smaller motors, gets about 5 mpg at 6 knots, and less at higher speeds.

[MicHughV]

something too compare ....I have twin Yamaha 150's on my fishing boat....they are 2.7 liters each, 4 cylinders....so a total of 5.4 litres and 8 cylinders..the engines are fuel injected....which I think will give better fuel consumption than a carb..

I have a fuel meter on my boat, lets me know my fuel consumption at any rpm...

At cruise rpm.....about 3,200 rpm..I burn about 15 gal/hr for both engines...doing about 30 mph....this equates to about 2 miles per gallon....at cruise....

at lower speeds, the engines turn less rpm, but the boat is struggling to get on plane, so that fuel consumption is more or less the same..

at wide open throttle, about 5,500 rpm, fuel burn jumps to around 45 gal/hr...

I don't think the Corvette engines will be much different. While in car, they might only be turning 1,800 rpm at cruise....in a boat, they will be turning in the 3,000 rpm range....

and you've got two of them.

finally, most marina's only sell ethanol free gas, as the ethanol does not like plastic..non-ethanol gas at the marina is currently about $4.50/gal....you can get it slightly cheaper at a gas station, if you trailer the boat there..

my guess is 1 mile/gal for both engines at cruise...I know other fishing boats with larger engines (pair of 300 hp engines), and 1 mile/gal is about their fuel burn rate...

realistically, that is what you will be looking at...outboards, corvette engines, little difference...both will suck gas...

a day's fishing for me, can easily burn $200 of gas....bursts of speed, coupled with some slow trolling...2 mile/gal average,.....in a pleasure boat, with twin corvette engines, 1 mile/gal....maybe less, if you are hard on the throttle...

[rsn48]

Speed is addictive so if you are jumping from sail to power boat, don't try out the boat with semi-displacement hulls that plane. The fuel used in faster boats is crazy compared to trawlers and sailboats.

But............... it is so nice to get to places faster. Faster gets you to marinas and anchorages earlier than others. Faster means you get to explore, wander, drink, sloth earlier than others. The cruise I do in my sedan cruiser in two hours would take sailboats and trawlers over 6 hours, sailboats usually longer if sailing (tacking and jibing). My boats top speed is 30 knots, efficient cruising on plane is around 21 knots.


Speed is wonderful, paying for it, not so much.

[mohave_steve]

Originally Posted by rsn48

But............... it is so nice to get to places faster. Faster gets you to marinas and anchorages earlier than others. Faster means you get to explore, wander, drink, sloth earlier than others. The cruise I do in my sedan cruiser in two hours would take sailboats and trawlers over 6 hours, sailboats usually longer if sailing (tacking and jibing). My boats top speed is 30 knots, efficient cruising on plane is around 21 knots.


Speed is wonderful, paying for it, not so much.

Well...... I thought I wanted a power boat but RSN48 has just about convinced me to stick with sail.....

[MicHughV]

There was a time, when I was considering a trawler.

Typically, these have twin diesels of various makes.

Though they "only" cruise at say.....8-10 knots...their fuel burn is quite high...give or take....4 gallons/hr...

Cruising at a faster speed, off course, means, bigger engines and more fuel burn......at the end of the day, I had to say no thanks..

[rsn48]

Well...... I thought I wanted a power boat but RSN48 has just about convinced me to stick with sail.....

Remember 7 knots in a trawler is faster than 7 knots in a sailboat.

[CassidyNZ]

In a previous life I owned a 24ft Bayliner that had a Ford V8, can’t remember the exact size but it was about 350cu.in. I learned two things from that boat.

1) Most of the fuel is used getting the boat onto a plane - try not to stop unless you must.

2) I will never, ever again own any boat, even if given a new one for free, that has any form of gasoline engine. It was the quickest wealth-depleting device I have ever owned.

But I agree with deblen, the small-block Chevy V8 is one of the greatest engines ever built. I worked for a General Motors a while back and I recall about 6 years ago, a newsletter containing an article that spoke of an engine being plucked off the production line and placed in a glass case in the reception of the GM headquarters. The reason? The engine number decoded to the 100-millionth small block V8 built by GM.