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What to Consider When Deciding Whether to Replace or Repower Your Boat Engine

Suffering from soaring maintenance costs, reduced performance or missed trips from engine failure on your boat? If so, you may consider whether to rebuild or completely replace your engine. Among the many factors to consider, boat owners should weigh the financial, technical and operational benefits when making such a decision.

One of the major advantages of rebuilding an existing engine is that the initial capital cost is likely less than replacing it altogether, in some cases. It’s important to research the availability and cost of replacement parts for an older model engine, along with the time it will take to complete the rebuild. If your boat needs to be on the water to run a business, this may not be in your best interests.

Depending on whether you choose to undertake the rebuild yourself, and the actual engine your own, there may be some calibration or complicated works that need to be done by a qualified mechanic. These costs also need to be factored in when weighing up your options.

While the benefits of rebuilding an existing engine are many, opting for a complete repower is also a viable solution. The electronic engine control and fuel system technology available today offers operators significant advantages in engine performance, monitoring and control — more specifically less fumes, better vessel acceleration, maneuverability, and the reduced consumption of fuel. Additionally, a repower provides the opportunity to increase propulsion power and vessel speed.


Technical factors in an engine repower

If you choose to repower your vessel with a new engine, several considerations should be made:

1. Propeller — If the power outputs are different on the replacement engine, operators may need to modify or change the propeller characteristics to obtain the desired vessel performance.

2. Transmission — If you plan to change the engine but keep the existing transmission, it is paramount to ensure that the transmission is rated to handle the torque and rpm of the new engine.

3. Driveline — You should ensure that the existing shafting is of sufficient torsional yield strength to handle the power and torque of the new engine. This is determined by both the shaft material and the diameter of the shaft.

4. Installation — The overall footprint of the engine, as well as any potential component or mounting modifications must be carefully considered. When looking for a new engine model, review available installation requirements and engine specifications regarding exhaust, radiated heat, air consumption, seawater inlet restriction and fuel inlet restriction. These items are critical and may necessitate additional modifications to ensure proper installation.

5. Engine and transmission controls — If you choose to change or keep the existing engine and transmission controls, compatibility with the new engines must not be overlooked.

6. Serviceability — Once everything else is accounted for, ensure there is sufficient space or access in the engine compartment to perform maintenance on the new engine.

Financial and operational considerations of an engine repower

Beyond the upfront capital cost of the project, you should consider the financial impact of replacing versus rebuilding their engine. These can include changes in maintenance periods and fuel costs. When evaluating maintenance costs, analyze the different prices of parts, as they can differ greatly between brands. One way to do this is through requesting quotes for the price of regular maintenance parts from your engine retailer.

Another aspect to investigate is the possibility of financial assistance or grants associated with complying with certain emissions standards. These incentives can often include financial assistance for the project as a whole, making the option of repowering a vessel extremely attractive. It’s best to check with your local authority or governemnt department on emissions criteria and the availability of any grants or financial assistance packages.

Other factors to be weighed are the operational advantages associated with predicted reliability, an increase in vessel speed, and a reduction in noise and visible smoke. For commercial boat operators, these key operating attributes are directly related to overall profitability, whether it be an impact on ticket sales or reduced downtime due to unscheduled maintenance.

In summary, it pays to carefully weigh the outcomes of whether to repower or rebuild propulsion engines. While there are many factors at play, if the decision-making process is done in a methodical and comprehensive manner, operators have a much higher probability of making the right decision.

Download and view our Yanmar marine engine brochure.

Download and view our John Deere marine engine brochure.

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