Getting the Best Performance from Your Boat’s Outboard Engine

If you take the time to properly install and maintain your outboard engine, it can be an efficient means of propulsion for your boat. As a boater, you should consider factors like:

• Selection of the boat propeller
• The required RPM range
• Complying with maintenance schedules recommended by the manufacturer

Installing a jack plate or other performance upgrade will boost your boat’s capabilities, but these upgrades come at a price. For instance, the cost of a hydraulic jack plate may range from $600 to $2,500.

Thankfully, there are some low-cost options available to you to make your boat’s outboard motor engine perform better.

 

How to Improve the Performance of Your Boat’s Outboard Engine

1) Prop the Boat Correctly

If your boat is over-propped, your outboard will only be able to reach a lower maximum RPM than the manufacturer-recommended RPM when the throttle is wide open. As the pitch increases, greater water resistance is encountered, preventing the propeller from spinning with maximum freedom. If you want to be absolutely certain, consult the manual for your vehicle, although typically the maximum RPM at full speed is between 5,000 and 6,000.

The engine will have to work harder if you keep your RPMs below the suggested range. An increase in combustion temperature due to the boat’s greater workload equals increased stress on the vessel’s components.

It’s also dangerous to have your boat under-propped above the optimal RPM range, engine wear increases, reducing the engine’s lifespan. Changes in propeller pitch affect the maximum engine speed achievable at wide open throttle. The wide-open rotational speed can be slowed by increasing the propeller pitch or sped up by decreasing it.

Trying out various propellers is also recommended. Use whatever budget-friendly propellers you can get to get where you want to be in terms of performance.

You can use a tachometer to conduct a wide-open-throttle test. This will help you determine if your boat is hitting the recommended RPM range. Most boats are already equipped with a tachometer.

 

How to Conduct a Wide-Open Throttle Test

Step 1: Use the boat as you normally would, with the usual amount of equipment and number of people.

Step 2: Make sure that about two-thirds of the gas tank is full. Run the boat when the water is calm and there aren’t many other boats around so that the results are not affected.

Step 3: Go full throttle in a straight line and trim out the motor until you hit the maximum speed.

Step 4: Note down the RPM; once done, stop the boat.

Step 5: To account for tides or wind, repeat the above steps going in the opposite direction to the water flow with maximum boat speed, and take the average of the two RPM readings.

If the average RPM is not in the centre of the WOT rating, you might need to change the propeller for one with a better pitch.

 

2) Treat the Fuel to Avoid Corrosion

Phase separation, the process by which water in the fuel is separated from the fuel itself, is a major reason why ethanol gas is bad for boat engines. For obvious reasons, this is a bigger issue on boats than in cars, since gas usually stays considerably longer in a boat.

 

But ethanol can still cause corrosion damage, even if boat owners use their vessels frequently and replace the supply every few weeks. You should still use an additive even if you can get gas without ethanol. Condensation can form in boat fuel tanks even when they are only partially filled, and water in the gasoline supply has been an issue for decades, long before ethanol was introduced.

Possible issues with interior corrosion can significantly diminish an outboard’s usefulness.

 

3) Trim the Boat to for Peak Performance

When boats run parallel to their waterline at rest, they are most manoeuvrable; you will experience a comfortable ride, high speeds, better gas mileage, and overall good performance. The angle at which the bow of the boat enters the water correlates directly with the efficiency with which you manage your vessel.

To optimise your boat’s performance and durability, reduce the positive trim on your boat. Make sure that the outboard lower unit’s nose is pointed directly forward. This causes the propeller thrust to travel directly aft. For readers new to the term ‘aft’, it implies “toward the ship’s stern drive (rear).”

Outboards or trimmed-out lower units have their noses pointing downward, and thrust is directed upward. Thus, the push is not forward, resulting in decreased efficiency and increased fuel consumption.

 

4) Do Away With the Rooster Tail

During a race, regardless of the type of boat, the most efficient ones can be identified by the lowering rooster tail upon acceleration. When stepped-V bottoms or high-speed catamarans are going at higher speeds, they have almost no rooster tails.

If the rooster tail of your boat goes down as you make modifications, you are likely getting things right.

Having said that, certain propeller brands may also result in relatively higher rooster tails. Consider the boat’s weight distribution as well as the height of the engine. Experiment with various modifications; if the rooster tail decreases with every boat ride, you’ll know you are heading in the right way.

 

5) Regularly Replace Oil and Filters

An outboard-powered boats consistently operate at high RPMs – considerably higher than those of trucks or automobiles. With 4-stroke engines, keeping the engine oil clean and fresh is of the utmost significance, and replacing the oil filter every time will assist keep the oil even cleaner.

There is no need for oil changes or fuel filter replacements with 2-stroke engines, which makes maintenance significantly cheaper. In high-use applications for outboard engines, 2-stroke engines are significantly more economical.

 

6) Practice Filter Maintenance Best Practices

The purpose of gasoline filters is to prevent water as well as other impurities from entering the fuel system. Outboard engines require water-free gasoline for optimal performance. Typically, the manufacturer will provide advice on how frequently you should replace filters.

Gasoline filters should be replaced every six months as a general rule, although they may need to be replaced more frequently based on factors like fuel colour and vacuum gauge readings.

If your fuel is a muddy brown hue, this indicates that pollutants are entering your fuel system and that it is time for you to replace the fuel filter.

When measuring a vacuum gauge, there are three zones that are colour-coded. Green represents the good area, yellow represents the borderline area, and red represents the bad region. Consider replacing the gasoline filter if the needle of the fuel gauge is in red or even yellow region. After replacing your fuel filter, you will most likely observe an improvement in performance and top speed.

 

7) Assess the Hull for Any Fibreglass Work Requirements

Finding a rocker or hook in the hull bottom, both of which reduce efficiency, is best done using tape and a straightedge. Running surfaces with a hook are scalloped or include a depression just beyond the transom. This forces the bow down and reduces speed in the same way as if enormous trim tabs were down. Put a straightedge upon the running surface forward of the transom to check for the hook; a level measuring three to four feet is ideal. There is a hook that needs to be repaired by filling and putting fibreglass if there is a gap between the bottom and the straightedge.

Rocker, the opposite of a hook, is built into the hull to make the boat heel back onto the stern of the running surface, where it can more easily bear the bow while cruising or travelling at high speeds. It is important to check for the hook and rocker.

 

8) Use the Outboard

Allowing an outboard to stay idle is dangerous. Seals contract, oil attracts dust, condensation forms, and components corrode. One of the worst things that can be done to a marine engine is letting it sit idle for long periods of time.

When a boat rests for more than two weeks, the owner must start it and allow it to idle until it reaches operational temperature. If you ever needed an excuse to utilise your boat, this is a good one.

 

How Can I Increase My Motor Boat Speed?

Simply by reducing the boat’s weight, you may be able to increase the speed of the boat’s engine. Remove everything from your storage area, apart from the bare necessities. When a boat is lighter, acceleration is quicker, and drag is minimised since the hull height is greater in the water. To minimise weighing down the bow, heavier objects should be stored in the aft compartments. You can also enhance speed by draining the fresh water and holding tanks, and launching your boat with less than a full fuel tank.

 

Can I Increase RPM by Raising my Outboard?

Elevating your outboard can enhance your RPMs by lowering the amount of drag. However, raising the outboard too much can result in slip-on acceleration and propeller ventilation.

 

Can a 4-Blade Prop Increase Boat Speed?

A 4-blade propeller is optimal for maximizing thrust from your boat’s engine and achieving a smoother cruising experience. However, compared to 3-blade propellers, 4-blade ones can sometimes slightly reduce the boat speed.

 

Wrapping Up

Improving your outboard motor’s efficiency doesn’t have to cost you a fortune. The trick is to keep experimenting with the equipment until you find the one that produces the best results. Regular maintenance is also vital for ensuring your boat’s efficacy and performance.