GAS VERSUS DIESEL

Q: I have a 1988 Sea Ray 270 Sundancer with twin 4.3 Mercs that I’m going to repower in a couple of years. Do you know if anyone has done a repower from gas to diesel? I’m interested in going to diesel to get away from the alcohol in our fuel. I’m looking forward to seeing the pros and cons of this change in a future issue of boating.

John George Brandon, Canada

A: Mr. George, while individual installations will vary, here is a general comparison chart.

PROS FOR DIESEL:

1. No problems associated with ethanol and storage.

2. A torquier engine will swing a larger prop and offer more control, especially in rough water and while docking.

3. Since a diesel offers more torque, a small-horsepower engine can be used; often a straight-six or even a pair of fours can replace a pair of V-8s and deliver performance comparable to the big-block gas engine.

4. Less chance of explosion, fire and carbon-monoxide danger (though, these are not eliminated).

5. Increased range and better fuel economy of maybe 30 percent. Keep in mind, diesel fuel often costs more than gasoline—currently, about 20 percent—which negates some of this economy when considered as an operating cost.

CONS FOR DIESEL:

1. More expensive purchase price. Expect to pay easily up to twice as much for comparable diesel engines versus gas (horsepower ratings will be different because of torque ratings). You’ll need new drives because your old drives won’t stand up to the torque. You will likely need to modify your engine box to deliver more ventilation because diesels need more air.

2. Noisier.

3. More expensive to service and repair.