Attaching Boat Engines: A Step-By-Step Guide

Setting up a boat engine is a complex task that requires careful consideration of various factors. Whether you're dealing with an inboard or outboard engine, the process can vary depending on the type and size of the boat, as well as the specific engine model. For example, the height of an outboard engine can significantly impact speed and fuel efficiency, while inboard engines often use closed-cooling systems similar to those found in automobiles. Additionally, electrical wiring and circuit protection are crucial aspects of the setup process, ensuring the safe operation of the boat's electrical systems. Ultimately, each step in the setup process influences the other, and fine-tuning is often required to optimize performance.

Setting the outboard height

To determine the ideal outboard height, start by aligning the anti-ventilation plate slightly above or at the same level as the bottom of the boat. This will ensure that the engine is not set too low, creating unnecessary drag. However, be careful not to set the anti-ventilation plate below the bottom of the boat, as this will act as a planing surface, lifting the stern and pushing the bow downward, compromising the boat's handling and performance.

If you are re-powering your boat with a new engine, consider the relative size of the new engine's gear case. A larger gear case will create more lift and run higher, so you may need to adjust the outboard height accordingly. As a rule of thumb, you want to ensure that the propeller has a good bite on the water without ventilating, especially when turning or navigating steep seas.

Finally, remember that the choice of propeller is also influenced by the outboard height. If you raise the engine height, you can add propeller pitch to further enhance fuel efficiency and speed. Conversely, lowering the outboard may require reducing the propeller pitch to maintain optimal performance. Fine-tuning these parameters through sea trials and subsequent adjustments will help you get the most out of your boat's setup.

Wiring the boat

Wiring a boat is a complex task that requires careful planning and execution. Here is a step-by-step guide to help you through the process:

Electrical Source: Battery

Firstly, understand that electricity in boats is typically stored in one or more batteries. These batteries are charged by the engine's alternator or an auxiliary battery charger. There are two main types of batteries: starting batteries, which have high current rush capacity, and deep cycle batteries, which can withstand deep discharge without damage. Depending on your boat's setup, you may have a single engine with one starting and one house battery or a twin engine with two starting and one house battery.

Main Battery Switch

Your boat wiring system should include a marine-grade main battery disconnect switch, allowing you to turn off everything at once in an emergency. This switch lets you select which battery to use and can also parallel both batteries to charge them simultaneously or assist with starting the engine. Remember to switch to the "house circuit" when the engine is off to draw power from the deep cycle house battery.

Battery Switch Bypass Loads

It is standard practice to bypass the main battery switch for critical components like the bilge pump float switch. This ensures that even if the main battery switch is off, the bilge pump will activate if the boat starts filling with water.

Getting Power to the Helm

The next step is to bring power from the house battery to the switch panel. Use marine-grade primary wire in an appropriate gauge (AWG) for this purpose, considering the length of the wiring run and the number of electrical loads. The positive wire from the battery switch (with a fuse) and the negative wire from the battery negatives should be connected to the switch panel.

Install a Terminal Block as a Breakout Point

If your switch panel is fully wired, it will have an easy-to-install wiring harness with heat-shrink labels and ring terminals. This connects to a terminal block, providing a breakout point for troubleshooting and future additions. The positives from the switch outputs are connected to the terminal block, while the negatives go to a negative bus bar.

Run Load Wiring to the Terminal Block and Bus Bar

Finally, connect your boat's existing wiring infrastructure to the terminal block and bus bar. Positives connect to the terminal block, and negatives to the bus bar. Ensure that the positives are installed on the correct gang associated with their respective switches.

Some additional tips to keep in mind:

• Always use a wiring schematic if available and make detailed notes of any repairs or modifications.
• Use colour-coded wires (red for positive, black for negative) for easier troubleshooting.
• Invest in high-quality connections, dielectric grease, and shrink tubing for connections.
• Ensure battery terminals are snugly tightened, with the smallest leads on the bottom to prevent shorts and optimise battery performance.
• Use cable lubrication when pulling wires through chases to avoid damage.
• Bundle wires with zip ties for organisation but use sparingly to avoid snagging during maintenance.
• Choose the proper wire gauge based on load requirements and distance from the battery.

Remember, wiring a boat can be a challenging task, and it is always recommended to seek professional help if you are unsure.

Mounting the outboard motor

Step 1: Measure the Transom

Before mounting the outboard motor, it is crucial to gauge the height and thickness of the boat's transom. The mounting height of the outboard motor will significantly impact its running speed. If the height is too high, cavitation may occur, leading to speed issues, energy waste, and propeller damage. On the other hand, if the height is too low, water resistance will reduce speed, energy efficiency, and overall performance. The optimal height aims to keep the anti-cavitation plate between the bottom of the boat and a level 25 mm (1 inch) below it.

Step 2: Choose the Right Shaft Length

Different transom heights require different shaft lengths for your outboard motor. Refer to a shaft length chart to determine the appropriate shaft length for your specific transom height. If you still have trouble reaching the water, consider installing an outboard motor bracket.

Step 3: Assess the Transom Thickness

Ensure that the thickness of your transom is within the range of 30 to 70 mm. This step is crucial, especially when re-powering an older boat, as the transom's structural integrity may have deteriorated over time, especially if it is made of laminated plywood. Ask your dealer to check and advise on the transom's condition before proceeding.

Step 4: Mounting Process

Now, you are ready to mount the outboard motor. Here is a step-by-step process:

• Center the Outboard: Place the outboard motor on the centerline (keel line) of your boat to ensure proper balance. If your boat has an asymmetric shape, consult your dealer for guidance.
• Secure with Clamp Bolts: Position the outboard motor as close to the center as possible and firmly tighten the transom clamp bolts. Use stainless steel bolts to prevent rust, and ensure they are tight to avoid any loose motors that could cause a loss of control or injury.
• Attach the Motor: Mount the motor to the mount, ensuring it is secure and firmly latched.
• Finalize with Screws: For added security, use two screws to fix the outboard to the boat. This step is especially important for gasoline motors, which tend to require a firmer mount.

Step 5: Test and Adjust

Finally, test the outboard motor through sea trials and make any necessary adjustments. Fine-tuning the setup may require some educated guesswork and field-testing, but it will ensure optimal performance for your boat engine.

Installing an auxiliary outboard engine

Auxiliary outboard motors, also known as "kickers", are useful for powerboaters in two main ways: as a backup in case the main engine fails, and for alternative propulsion when the main engine is too fast for slow-trolling. Anglers in the Pacific Northwest and elsewhere find them extremely useful when slow-trolling for salmon and trout. Sailboaters also use kickers when sailing is impractical.

There are two main ways to install an auxiliary outboard engine: using a transom mount or a bracket mount.

Transom Mount

Some boats, such as Walleye models, will have transoms ready to accept the direct installation of an auxiliary outboard, allowing the kicker to tilt and trim. Smaller auxiliaries may be clamped onto some transoms, but through-bolting is recommended as the most secure mounting method. If you do clamp, be sure to include a safety cable, as auxiliary engines do not float.

Bracket Mount

Larger boats and most fibreglass saltwater models will require the use of a bracket bolted to the transom to mount the auxiliary engine. Most engine brackets are spring-loaded, with the heavy spring making it easier to raise and lower the outboard. Compare the throw of the bracket spring to the transom height at the mounting location and the shaft length of the engine before installing.

When installing a bracket mount, you will need to choose the most appropriate side of the transom. Since the outboard tiller is usually on the port side of the motor, most kickers are mounted on the starboard side of the transom to facilitate easier tiller steering and throttle control while slow-trolling or putting home. Make sure the position allows for through-bolting of the motor bracket and does not interfere with the operation or swing of the sterndrive or main outboard.

To install the bracket, you will need to mark and drill holes in the transom, and then bolt the bracket securely in place. When marking the hole locations, check for interference from hoses and wires on the inside of the transom. Use a marine sealant such as 3M 4200 on the inside of the mounting flange and backing plate to prevent water intrusion, and use stainless-steel bolts, washers, and locknuts for durability.

Once the bracket is installed, mount the motor using the lower mounting holes on the outboard bracket to through-bolt the motor. This is more secure than relying solely on clamp brackets, which can vibrate loose over time. Use stainless-steel bolts, fender washers, and locknuts to secure the motor.

Starting a boat motor

Firstly, ensure the engine is tilted fully down. This will make it easier for fuel to reach the carburetors. Next, squeeze the primer bulb until it feels firm. This step is important to get fuel into the motor. Check for any fuel leaks after this step. Then, advance the throttle in neutral to about two-thirds.

Now, you can turn the key on and push to choke (or pull out the choke) while cranking the engine. Once the engine is ignited, release the choke and return the throttle to the neutral position.

It is important to ensure the fuel tank is vented. For built-in tanks, check that the vent fitting is not obstructed by anything, such as an insect nest or wax.

If you are using a manual choke, you will need to activate the choke button or lever. This restricts airflow to the carburetor, allowing the motor to start in low temperatures. If your motor has an automatic choke, simply push the key deeper into the ignition.

If you are starting a 2-stroke outboard engine, you may need to follow a different procedure. Here is a basic 5-step process:

• Engine tilted fully down.
• Squeeze the primer bulb until firm.
• Advance throttle in neutral to 2/3.
• Turn the key on, push to choke (or pull out the choke), and crank simultaneously.
• Release the choke and return the throttle to neutral after ignition.

It is worth noting that boat engines require ignition, fuel, air, compression, and exhaust to start up and run smoothly. If any of these elements are missing or blocked, the engine may not start.

Frequently asked questions