Speed/gallons per hour

[Nav203]

Planning a family vacation aboard our 1975 Pacemaker 32' Flybridge with twin Chrysler 318's, gasoline. Destination will depend on fuel consumption rates. Can anyone help with rough idea of what she'll burn, and what speed through the water we'll get at, say, 1,500 rpm easy cruise, and then 2,700 on plane? Never had to worry about this before, but it's a new world out there. Will be keeping careful notes this time on what she uses.
Many thanks!

 

[tommays]

Re: Speed/gallons per hour

With out fuel flow meters (which dont cost much compared to the current fuel price ) you will never find the best speeds as even a small speed change can affect things buy 1 MPG

 

[QC]

Re: Speed/gallons per hour

My guess is that 1500 RPM may be more than hull speed and may be poor economy, but I would bet around 8 gallons per hour and 7 MPH which is less than 1 MPG. Also, 2700 seems low for planing speed and if at all, so maybe 3500 RPM @ 30 GPH combined at 25 MPH for less than 1 MPG again . . . I could be off a lot though.

Tough to find good data for older engine and boat combos. Today's 30 - 35 foot planing hulls (express cruisers) typically run 40 MPH top speed and use MPI engines that get better efficiency and exhibit sometimes much better numbers than above. I based my guess on a couple of 32 footers and a 36 footer with twin 320 bhp and 420 bhp respectively. I know that sounds like a poor comparison, but the older carbed inboards will probably do a lot worse than the 32's and may be as bad as the 36 . . . You should surf BoatTEST.com for more data to make yourself feel better.

 

[Nav203]

Re: Speed/gallons per hour

Many thanks for the help! Yes, am finding that it IS hard to find info on the older boats including this one, with the most info coming from the wise old hands in the local yards who have had experience with this model. The concensus is that she'll get between 1-2 mpg, although possibility of a little better given some fine tuning of throttles and tabs. The boat does plane at 27, though it takes 3,100 or so to get her out of the hole then can throttle back. Am going to start working on a usage curve this trip, then invest in a flowscan when we get back. Again, thank you all!

 

[jay_merrill]

Re: Speed/gallons per hour

I agree with QC. Unless you run at very low speeds all of the time, you will probably average about 1 mpg in that boat.

 

[sidthekid]

Re: Speed/gallons per hour

You don't have to invest in a Flowscan. Lowrance makes fuel flow sensors that are one third the cost and more user friendly. I would reccomend one for every boater out there. Anything else and you're just guessing and probably wasting fuel. You would be surprised at what 200 rpm will do for fuel rates. For example, my boat burns less fuel cruising at 29 mph then it does cruising at 27 mph! Buy the fuel flow sensor, it's basically free. What you end up saving in fuel costs will pay for the sensor many times over. Mine paid for itself in half a season.....Sid