1984 46 post fuel consumption estimates

Hello, welcome i am also new to post have some input for you. I have an 88 46 Post but i have the 6v92 with 550hp. I bought it in north St. Petersburg and drove hit home to Miami. I hold about 630 gallons of fuel and if my math was correct i wasted between 28-32 GPH on the trip home cruising at 20knots. Hope this helps and welcome you’re going to fall in love with the Post i have.

What engines are in it? 6-71 TA's? 25 gph seems awefully hopeful. 30-35 GPH sounds about right for the pair. But I don't have a lot of experience with the 6-71's

I attached a fuel graph for 671 TIs
I understand if your engines are running correctly and you can get max load WOT your fuel burn is going to be really close if not exact.

I have 671 TIBs and I follow this graph pretty closely.
I don't have floscans.
I always round up to 2 gallons per nautical mile at cruse when planning a trip.
I burn less fuel, but I round up for math and safety margin.

At the end of the trip I always seem to have left over fuel and
fuel burn seems on or close to the below fuel burn graph.

I have an 84 43, with the same engines. You will burn in the low 30's per hour at 2000-2100, matching the graph above. You can run 10-12 hour days, with your fuel tankage. A 200 mile day is probably a safe maximum. Keep your plans very tentative and flexible. Weather, this late in the year, is tougher and may force you inside if you have to keep moving. Congrats and best of luck with the trip!!

Yes, less load equal less HP demand (at a given rpm) and less fuel burn.

22-26 total ship?
At 2100RPM, your under loaded.

Think of this as stuck in second gear on a three speed.
Lets double check your wheel sizes and reduction.

Well what speed/rpm are you making at WOT with full fuel/full water and gear......let's start there.

Also rcrapps, he has 6-71 TIB's and if memory serves me right (it's been a long time) cruise is 2400 and WOT is 2800 rpms.....so he's running under cruise rpms too. But the graph says 2500 rpms.......what is cruise rpms on these motors?

You know that sound of fingernails on a chalk board? Your back bones feel weak and you want to turn away?
A 71 spinning toward 2800 RPM has the same effect on me.
I think high idle @ 2500 and loaded @ 2450 should be the max numbers with a light boat.
Fast cruise from 2100 to 2200 RPM.

At 2100 RPM, I figure at least 350 maybe up to 375 HP if the wheels are correct. That should be around 35+GPH total boat (less gen-set).
The above graph seems a lil conservative to my reasoning. However, the graph and I do agree, He should be consuming a lil more fuel at 2100RPM .

Ah, but the rub; It's hard to do whole trips at speed. 6-71TIs or TIBs really don't consume mega gallons at lower RPMs.
Posterboy91 just quotes average.

If you're hitting 2600 with full fuel, water, provisions, and 4 guys. Yeah you're underpropped. Each inch of pitch drops 50 rpms.

What were your RPM's at 20 knots? Genset running? Thanks

I remember this old BlackFin I purchased.
The only set of props, probably original, were re-worked so many times they lost lots of blade area and diameter.
I was impressed with the new & correct props, how much larger they were over the old ones.
Oh, DaFin ran like a race horse. Finally able to apply HP to the water.

Would you have a spare prop set on board? Readable numbers?

Did the OP get his answer on probable fuel burn so he can paln his trip to FL?

Based on post #6, I assume he is here.

671 TIB max WOT is 2550 RPM under load

You need more wheel.

Then I'd just leave the wheels the way they are, a touch under propped is better than over propped.