Spending time out on the water in your new boat is a great way to relax, de-stress and have some fun. However, owning a boat is similar to owning a car. You’ll need to understand the basics of engines, electrical systems, and many other aspects of your boat before you head out onto the lake or ocean for the day.
Whether you’re running a high-performance boat like a bowrider for watersports, or a bass boat for fishing, you need to understand the components of the watercraft to achieve the best performance and longevity out of the vessel.
The engine is a complex piece of machinery. While you don’t need to understand the mechanics of its operation, you need to know what it requires to run at peak performance. The fuel you use in the motor directly affects its output and the longevity of its components.
However, with so many different grades of fuel available and with gas prices soaring, you have to know the right fuel for your machine, or you’ll end up damaging the engine, causing a costly replacement or repair.
This post looks at the different types of fuel available. We’ll unpack the characteristics of each fuel and make our recommendations on the right blend for your boat.
Contents
Personal Boats and Watercraft
If you have a personal watercraft like a waver runner or jet ski, you can fill the tank with the same gas you use to fuel your car.
PWCs operate on 87 Octane unleaded gas and 89 and 93 Octane. This fuel grade is also suitable for use in smaller personal boats like Jon boats and bass boats that feature trolling or outboard 4-stroke motors.
We recommend going for 93 Octane if you have the budget. This fuel gives your engine the best performance, and there are fewer impurities in the fuel requiring less maintenance of the fuel lines, jets, or carburetor. However, these ethanol-free gasoline products are expensive, and there are cheaper options for running your boat.
The key to selecting the right fuel for your PWC is avoiding using blends high in ethanol. Ethanol damages the engine, ruining its service life.
Commercial Watercraft
If you have a yacht or a larger commercial vessel, you probably have moors that run on marine diesel oil (MDO) or marine gas oil (MGO). Unfortunately, you won’t find either of these fuels available at the local marina.
MDO is a fuel containing heavy diesel oils. This fuel isn’t the same as what you put in your pickup truck, and you’ll only get it from ports and other industrial locations serving larger commercial watercraft.
MGO is a blend of aromatics and lighter cycle gas oils. This fuel may also contain waste products from the fuel distillation process or used motor oil.
Check the Owner’s Manual
Before you fill up your boat’s tank for the first time, consult with the dealer about the right fuel, or look it up in the owner’s manual. We always recommend looking it up in the manual because you don’t know the experience of the sales rep, and they might give you the wrong information if they don’t know what they are talking about.
Your owner’s manual specifies the right octane fuel for the engine. High-performance boats and engines require a minimum of 87 octane fuel to ensure you get the best performance from the watercraft and keep the engine in optimal running conditions.
Before filling the tank for the first time, check the fuel filter. Your boat should have a 10-micron water-separating fuel filter in the line between the engine and the tank. This filter prevents contaminants from getting into the motor, damaging its components.
Oil Filters and Fuel Stabilizers
We recommend you keep a spare oil filter on your boat. Check with the manufacturer or dealer for the right size filter for your engine. Use a marine-specific fuel stabilizer compound mixed to the right ratio to prevent phase separation and oxidation of the fuel.
Most modern fuels will start to separate after around 15-days, and adding a stabilizer to the fuel limits the separation, extending the shelf life of the fuel.
While modern fuel injection engines have less trouble handling separated fuels, owners of carburetor models will experience malfunction when trying to run the motor using separated fuel.
Fuel Injection Vs. Carburetor Engines
Fuel injection systems are pressurized, closed systems. Therefore, the fuel never comes in contact with air, and there is little oxidation taking place, even with extended time in the tank.
However, with carburetor models, the fuel moves through a vented system. As a result, any fuel trapped in the float bowl oxidizes rapidly, especially if you’re storing the boat in warm temperatures. The fuel with separate and turn lumpy, causing you to flush the system to remove the ruined fuel.
Should You Avoid Using E15 Fuel?
You might have heard other boat owners talking about how they use E15 fuel in their motor. It’s becoming more popular with boat owners, but is it the right fuel blend for your boat?
We recommend avoiding the use of E15 fuel in your boat. Many boats operate with E10 fuel, so there are a lot of boat owners that make the mistake of thinking that they can use E15 in their fuel tank. Using E15 will ruin your motor, and the Environmental Protection Agency (EPA) recommends that boat owners avoid using the fuel to power their vessel.
So, what will happen to your motor if you fuel it with E15? E15 fuel consists of 15% ethanol, and this fuel is highly corrosive on your motor components. As a result, you’ll find you experience frequent failures in the motor components and clogs in the fuel filter.
If you continue to use the fuel, it will eventually cause leaks and cracks in the fuel tank and the fuel lines, presenting a severe fire hazard. The last thing you need is your boat bursting into flames when your miles out to sea.
Make sure you’re using an approved fuel for your boat. The four common types of fuel for boaters are the following options.
- E10.
- Ethanol-free Gasoline.
- Diesel.
- Oil and Fuel Mixtures.
E10 Fuel
Initially, fuel manufacturers mixed E10 with Methyl tert-butyl ether (MTBE), causing problems for boat owners. Boat engines don’t have the design necessary to run on this fuel blend, causing issues with the motor components, filters, tank, and fuel lines.
However, in recent years, fuel manufacturers altered the E10 blend, and now boat owners can use it safely in their engines without the threat of disrupting or damaging the fuel system. However, before you fill up with E10, check with the dealer and the motor manufacturing brand to see if it’s compatible with E10 fuel.
E10 fuel is readily available at gas stations and marinas, and it’s the most affordable fuel you can buy for your boat. If you have a gas-powered engine on your boat, it’s likely compatible with E10 fuel.
If you’re making the switch from ethanol-free fuels, we recommend emptying any remaining fuel from the tanks before refueling with E10. It’s important to bleed the fuel system of all remaining ethanol-free fuels before filling with E10, or you run the risk of motor malfunction during use.
Ethanol-free Gas
As mentioned, ethanol-free gas is the best option for boat motors and PWCs. However, it’s expensive to run the watercraft using these fuels. The cost of gas almost doubled in many parts of the US during 2021, and it shows no signs of slowing down in 2022.
Ethanol-free gas doesn’t have the same corrosive characteristics as ethanol-based fuels, extending the longevity of the motor components for better service life. It’s also important to note that you shouldn’t use ethanol-free gas in motors previously running on E10 fuel.
Ethanol-free gas uses a chemical additive methyl tert-butyl ether (MTBE) to enhance the octane profile of the fuel. The additive can cause blockages in the fuel filter, affecting the performance of the motor.
Diesel Fuel
Most outboard motors run on gasoline, but more manufacturers are starting to use diesel engines due to the efficiency offered by this fuel. Typically, diesel engines feature on larger yachts and commercial vessels.
While diesel might cost more than ethanol-free gas or E10, it’s way more efficient. If you use your boat frequently, you could net huge cost savings on your fuel consumption over the year.
Diesel-powered motors also offer you more horsepower and torque, and they are more robust than gasoline engines, giving you a long service life than the gas-powered counterpart.
Oil and Gas Mixtures
Some boat engines may require a gas/oil mix, especially older models. The addition of oil to the fuel lubricates the components in the motor, preventing friction and overheating of the motor during use. As a result, the engine runs smoother, with less noise than gas-only or diesel models.
Oil/gas ratios for motors vary between manufacturers. Therefore, check your owner’s manual or ask the dealer for the right fuel /oil ratio before filling the tank. We recommend using marine-grade oils for the best performance for your motor.
Choosing the Right Marine Oil
Most manufacturers recommend you use oil suitable for four-stroke engines. The oil must meet FC-W certification guidelines for use in your boat. To check if the oil is compatible, look for the FC-W symbol on the can label.
FC-W guidelines include rust-protective additives in the oil with a higher viscosity than traditional motor oils you use in your car. Therefore, the oil remains more viscous when the engine warms up, improving the lubricating action of the oil on the motor components.
Two-stroke outboard motors requiring TC-W standard oils need to check that they use a product suitable for two-stroke motors, not four-stroke engines.
- Direct replacement for Mercury Marine 8M0078628
- Designed for use in 4-stroke marine engines
- Formulated to provide superior corrosion resistance and wear protection to maintain peak engine performance and reliability
- Special viscosity modifiers help to optimize the performance of high-rpm 4-stroke outboard motors
- 25W-40 viscosity
Top 10 Tips to Save on Fuel
With fuel costs rising across the United States, it’s a good idea to learn how to conserve your fuel. Follow these tips to save on the costs of filling your tank.
Anti-Foul Your Hull
Fouling on the hull, such as barnacles and tube worms, increases the drag on the boat, requiring the engine to work harder. As a result, you use more fuel while reducing the boat’s performance and the motor. Anti-foul your boat at the end of each boating season to keep the hull smooth and reduce your fuel costs the following season.,
Take It Easy
Apply enough power to get the boat planning, and then lean off the throttle to save on consumption. Power up and get the boat planning as soon as you leave the no-wake zone to save on fuel. Pushing your boat to its performance limit also drains the tank fast. Learn to ease back on the throttle and cruise.
Install a Fuel Flow Meter
Monitor your consumption, engine speed, and RPM output to find the ideal sweet spot where your engine offers you the best balance of speed and consumption. Installing a flow meter between the tank and the motor helps you motor your fuel consumption in real-time, helping you identify the best cursing speed for optimal fuel efficiency.
Check the Motor Props
The props are the driving force behind your motor. At the end of the boating season, pull the engine from the boat and send it to the machine shop for reconditioning and polishing. Leaving pucks in the props reduces the motor’s efficiency, increasing fuel consumption.
Watch Your Throttle Play
Using the Wide Open Throttle (WOT) range is the key to optimizing fuel efficiency and maximizing the performance and power of your motor. Check the owner’s manual for the recommended RPM level and select a propeller allowing your engine to reach WOT. Typically, this output is in the range between 5,000 and 5,500 RPM.
In Closing – Create a Log Book
We recommend using a logbook to track your fuel expenditure during the year. Tracking your fuel consumption on a spreadsheet helps you identify when your motor starts to drop in efficiency, letting you know when it’s time to service the engine while saving you on fuel costs.
