The one thing that keeps coming up time and time again is the great debate of Gasoline vs. Diesel propulsion. In this post I will address the Gasoline side of the debate since Tropical Horizons is powered by two very large Crusader Marine 350 hp. 454 carburetor fed engines. In this post I will share information that was gathered from our own personal experience and here’s the catch, not every boat is the same, but this should give some of you out there a good idea of what to expect.
Let’s start with Tropical Horizons herself; she is a true 41 foot deep V hull fly-bridge cruiser. What I mean by this is that she is exactly 41 feet from the stem to stern (excludes the anchor pulpit and swim platform). The hull is indeed a planing hull but her deep V configuration does give us good performance and directional stability at displacement speeds. For those tug and trawler owners out there ready to pounce on this post, remember to compare apples to apples and for the sailors out there, well when you get tired of living at an angle or pulling lines here and there and start to feel cramped in your living quarters, come over to the dark side.
So we know what kind of hull that Tropical Horizons has so just how heavy is she? Lucky for me I have just had some tonnage measurements completed and the she comes in at a net tonnage of 29.21. What about hull speed? Well calculated measurements taking into consideration a waterline length of 37 ft. give us an approximate hull speed of 8.15 knots. Why approximate? Well to be honest I had to guess at the waterline measurement since I didn’t have that figure, I would say that I’m fairly close. This is by no means the maximum speed that Tropical Horizons is capable of since she is a planing boat her max speed measured at WOT (wide open throttle) was 20 knots with a full fuel, water and provisions on board in choppy conditions.
So what about the numbers and what kind of range can we expect? What I did when we first acquired Tropical Horizons was install two fuel flow meters on the fuel lines feeding the fuel pumps on each engine. I did this because I didn’t trust the fuel gages and I wanted to be able to monitor fuel consumption and adjust the throttles accordingly in order to maximise range. All of the speed measurements are GPS SOG (speed over ground) measurements.
Now let’s have a look at trips we have taken and see just what our realistic range and fuel consumption.
Route | Distance | Fuel Used | Speed | Nm/gal |
Turkey Point to Port Colbourne | 49.92 nm | 61.86 gal | 8.18 kts | 0.8 |
Port Colborne to Port Weller | 25 nm | 20 gal | 6 kts | 1.25 |
Port Weller to Cobourg | 63.4 nm | 146 gal | 15 kts | 0.43 |
Cobourg to Trenton | 36.87 nm | 32 gal | 6 kts | 1.15 * |
Trenton-Belleville Return | 40 nm | 43.4 gal | 9 kts | 0.92 |
Trenton to Pine point | 10 nm | 15.9 gal | 6 kts | 1.59 |
Trenton to North Point Return | 40 nm | 46.1 gal | 15.2 kts ** | 0.86 |
Trenton to Picton | 36.56 nm | 48.3 gal | 8.66 kts *** | 0.756 |
Picton to Waupoos | 31.54 nm | 38.8 gal | 8 kts | 0.81 |
Waupoos to Loyalist Cove | 19.98 nm | 20.1 gal | 7.21 kts | 0.99 |
Loyalist Cove to Trenton | 53.15 nm | 52.6 gal | 7 kts | 1.01 |
*Running on a single engine as we had an over rev blowout on the previous leg.
**Ran up on plane at WOT 4000 Rpm 20 kts. Burning 20gph each engine this was the first test of our re-built engine after some time breaking it in.
***Ran up WOT to cross Big Bay and cut time off of our trip in order to arrive in daylight hours.
As you can see when we are running at low RPM under 1500, our fuel economy is actually quite good if you take into consideration full weight and loaded with provisions. What I did notice is that I have a problem with the Port engine carburetor as it will burn equally at WOT with the re-built Starboard engine but at lower RPM burns twice as much fuel. Rebuilding the Starboard Carb is one of my winter projects.
Just what kind of range can we expect from Tropical Horizons and her big blocks? With 400 gal of fuel and keeping a 10% reserve, running at 7 kts will give us an effective range of 360 nm. If we took a blended speed and consumption between 7 and 20 kts, we can expect a range of about 260 nm. All things considered that isn’t too bad.
The next thing I often hear is how much more expensive gasoline is over fuel, so I decided to have a look at various prices and found that overall, it really depends where you go but the cost difference is minor when you look at the big picture, the difference between gasoline and diesel is minor in most marinas. In fact I have found some marinas where gas was less expensive than diesel.
Now, let’s get down to how diesels like to run; that is, under load! When I owned a diesel work truck it was happiest when running hard and if you let it idle because you were working in -30 deg weather and you wanted to make sure you would get home, well that diesel just sucked back the fuel. Let’s face it diesels don’t want to run at low RPM. Gasoline engines don’t have that much of a problem running at 1000 RPM and lower all day long. If you take a look at planing hull boats, that diesel running at WOT is burning the same as the gasoline engine.
I also hear lots about how dangerous gasoline is, well get over it folks. Most of the same people who spout off about explosion risks of gasoline also have propane cookers on their boats….hmmm. There is a reason why bilge blowers, fume detectors, spark protected alternators and starters exist. Yes you guessed it, to keep boats from going boom! Many explosions caused by gasoline vapors all could have been avoided by following standard safety practices and using spark protected parts.
So we’ve had a look at fuel economy, cost of fuel, RPM, safety, what else is left? There is torque and this is a big one. This is where the diesels shine, their ability to turn a big prop without even blinking. On many boats there is a big advantage there, on ours, not so much. When we blew out the Starboard engine, we had a decision to make and potentially an opportunity, replace both engines with diesels, or simply keep the gasoline beasts. The diesel option really did not offer any real advantage to justify the cost. You see, our boat has prop pockets. What does that mean, well we can’t get a larger prop for a high torque diesel to spin, we are stuck with the 24” props we have, sure I could add more pitch, but the props I have are already at 24” of pitch which is decent. So would it be worth the extra $40K investment? I didn’t think so. But that is where it breaks down, torque is the key. With extra torque, you can have better low speed performance, get on plane faster and maybe even add an extra knot or two on the top end, but that’s it.
In conclusion, we have our gasoline beasts and as much as I curse them, I love them too! That’s the way it goes in boating. Tropical Horizons was the boat we could afford, with yes gasoline engines. When people ask me why I didn’t get diesels, I simply answer $50,000.00 that’s a whole lot of fuel. For those of you who have diesels, that’s great too! I’m happy for you! As for the sailors out there with your sails and rigging, I’ve been there before, when you want to take a break come on out with us and we’ll be happy to show you what the other side of cruising is like. What really matters at the end of the day is that no matter what you have; gas, diesel or sail, you are out there enjoying yourself and exploring the wonderful waterways that we all share together.
