Cost of running 5.0 5.7 7.4 Mercruiser...

BlackRocket · Dec 5, 2010

Those that have accurate knowledge...what is the cost or better yet, gallons per hour on a; 5.0, 5.7, 7.4 Mercruiser engine.

Thanks!

Summer Fun · Dec 6, 2010

Re: Cost of running 5.0 5.7 7.4 Mercruiser...

That question is hard to answer not knowing what size boat that they are in.

45Auto · Dec 6, 2010

Re: Cost of running 5.0 5.7 7.4 Mercruiser...

Why stop with just GPH data? Are you just going to ride around with no destination in mind? In that case, everything will burn 1 or 2 gallons per hour at idle.

On the other hand, if you're trying to get somewhere, would you rather have a 5.0 burning 5.0 GPH at 20 MPH (4 MPG), or a 5.7 burning 6.0 GPH at 30 MPH (5 MPG)?

Whether the bigger or smaller engine is more economical is very dependent on the boat and loading.

Boattest.com has lots of tests with fuel consumption figures.

The test below from one of the boating mags last summer compares a couple of the same boats with different motors.

themaniam1 · Dec 6, 2010

Re: Cost of running 5.0 5.7 7.4 Mercruiser...

Need more info on boat. I have a 24' Rinker cabin cruiser, Merc 350 Mg (5.7). WOT is about 20 GPH, 32 mph ~ 14 GPH and at 25 mph ~ 12 gph on clam smooth water at 6200 ft elevation. A lot depends on what and how you drive. Are you tugging people behind the boat? If so then you are constantly at WOT until they are up and that is like city driving. Cruising? At what speed? Are you trimmed out right? Sea conditions and wind also play a factor.

LippCJ7 · Dec 6, 2010

Re: Cost of running 5.0 5.7 7.4 Mercruiser...

as others have said its hard to say in general, but I ran on powell 50-53 MPH with 12 people in my boat and I went through about 25 GPH at the high end, we were pushing a 10 MPH head wind at my highest usage.
2000 Crownline 248 BR 7.4 MPI and a Bravo III
Hope that helps

rallyart · Dec 6, 2010

Re: Cost of running 5.0 5.7 7.4 Mercruiser...

Perhaps you are just wondering how the engines generally compare. Any boat engine is running under load all the time, unlike a car engine. You'll get very little vacuum if you measure that as a reference for load.
At any speed with any hull it takes 'X' horsepower to push through the water. With most engines there is not a huge difference in efficiency in the normal operating range. That means with most engines you need 'Y' amount of fuel to make 'X' horsepower. It is the same regardless of the displacement.
So, to make a particular hull travel 20 MPH it will burn the same fuel, roughly, with any of the engines you described. A more powerful engine will get a boat on plane quicker than a less powerful one and as a result use less fuel because it is not efficient to run a planing hull below a planing speed.
The trick of fuel economy is that, with a more powerful engine, you might choose to use the extra power to go faster. Then, the big engine will suck back much more fuel because it burns more when it makes more power.

Sharp Shooter · Dec 6, 2010

Re: Cost of running 5.0 5.7 7.4 Mercruiser...

I run a .30 over 7.4 in one of my boats and get about 15 minutes out of 26 gallons of methanol. Methanol bought by the 55 gallon drum is around 200 bucks.

I change oil (14 quartz) and filter about every other trip.

I probably top the chart in iboats when it comes to $dollar$ per gallon for use and it's worth every cent to me.

642mx · Dec 6, 2010