Hi!

I hope you are well.

I have a Phantom 25 1985 model straight V hull with a Mercury 450R. Max speed so far is 94 mph at 6,300 rpms spinning a Max5 ST 15,25 x 27 pitch prop.
Fuel prices in Norway are tough, and I am trying to find out how the 500R compare to the 450R in fuel flow in mid range 3000-4000 rpms.

My figures for the 450R are with one person:
3000 rpms @ 44 mph @ 40 litre / 10,5 gallon
3500 rpms @ 52 mph @ 50 litre / 13,15 gallon
4000 rpms @ 60 mph @ 61,5 litre / 16,2 gallon

Have you seen any tests for the 500R for fuel flow, or have first hand experience?

Look forward to hearing back from you.

All the best, Toffen

They seem to use a fairly significant amount more. In that area, Used to see about 2-2.1 mpg with 450s
now see about 1.65-1.7 mpg with 500s

I still have 450's, but lots of friends have noticed a significant increase in fuel consumption. And these are all re-powered boats (OB Cats), for a direct comparison.

Going from 1.7 to 1.3 or even less.

The launch reviews talked about 26% more boost, a bigger throttle body and much more mid-range punch than the 450R.

The differences in fuel economy in this thread indicate that the fuel curve is way richer in the mid-range. Very interesting...

Fuel is power. Power is fuel. Really no way to escape the laws of Conservation of Matter and Energy.

Thanks. Brad.

Yes but not always linear like in the above example. 10% more hp needs 20% more fuel.

UnderPSI,

Not only not linear, it almost seems exponential. The more HP we ask out of a given displacement, the more fuel per HP it takes to increase HP.

I struggle to understand why anybody’s not surprised the 500R doesn’t consumer more fuel than it does.

Thanks. Brad.

We are not talking about WOT fuel consumption.

We are talking about mid-range fuel consumption where the 500R apparently uses significantly more fuel than the 450R for the same horsepower.

Takes the same amount of HP to go the same cruising speed. That's why it's surprising the 500s are thirstier. Nobody is surprised they are at wot.

way more black soot on the back of motors after just cruising around at 75-80 mph. I'm surprised they meet emissions standards like this honestly.