carb switch question

[billallan]

I have a 305 volvo V8 (Chevy) currently running a holley 4bbl carb. It runs good. I can run 12 miles or so and then switch to Yamaha 9.9 kicker and fish for 4 hours or so then run back. I'm burning roughly 12 to 14 gallons of fuel. My question is could I do measurably better by switching to a different carb? I would like to keep comparable power. I've heard that holley's suck down the fuel.

 

[tschmidty]

Re: carb switch question

Probably not. But it does seem like you are burning a fair bit of fuel, but you don't say what kind of boat you are powering. A quadrajet will give better fuel economy at part throttle applications because the two main bores are smaller, wheras a holley has 4 equal sized bores. But I don't think it will help in a marine application, probably not enough to be worthwhile. A good tuning on the holley might help, or it could be something completely different causing your fuel economy to be low(ish).

 

[mkast]

Re: carb switch question

I've heard that holley's suck down the fuel.

Fuel equals power. Reduce the amount of fuel, the speed of the boat will decrease, all things being equal.
You don't mention how you measure fuel used, throttle setting, pitch of propeller or RPM.
When was the last time this engine was tuned up? Are you running the engine pasted peak torque?
A 305 didn't come with a Holley, as mentioned, was the carburetor tuned to the engine?
What do the spark plugs look like, i.e. color of the plugs?

 

[billallan]

Re: carb switch question

its on a 1977 Fiberform 19ft Cuddy, Running around 31-3200 RPM @ 27 Mph running 20pitch prop. I've owned the boat 1 yr. Not sure on the last tune up. It would have been at the most 3 yrs ago. I measure fuel usage by filling tank before leaving and filling on way back.

 

[dockwrecker]

Re: carb switch question

its on a 1977 Fiberform 19ft Cuddy, Running around 31-3200 RPM @ 27 Mph running 20pitch prop. I've owned the boat 1 yr. Not sure on the last tune up. It would have been at the most 3 yrs ago. I measure fuel usage by filling tank before leaving and filling on way back.

Fiberforms are built like TANKS! You've got a heavy boat there, fuel economy won't come easily if at all. On the plus side, that thing will probably survive a 40 mph beaching without a scratch. My ex father-in-law proved that up the San Juan at Powell in my 26' Fiberform Baja years ago.

 

[cr2k]

Re: carb switch question

If that is WOT RPMs you need less pitch in the prop. You are lugging the engine (and potentially damaging it). Should be running around 4400 at WOT. Borrow a few props 17p and a 19p and see which one works best for you.

So in other words, try a prop switch first.

 

[E4ODnut]

Re: carb switch question

What model Holley?
What kind of intake manifold?
What is your manifold pressure(intake vacuum if you prefer) at your cruise RPM?
Salt water or fresh?
Is the boat trailered or in the water all the time?