We get a lot of queries about repowering people’s boat engines. It can be a great way to soup up your boat’s performance, but there are a number of factors to take into consideration before you decide to go down that path.

1. What you want to achieve

A key aspect of making a decision about repowering is to understand exactly why you want to do it. Did you have a problem with the engine – did it overheat or run out of oil? Do you think you can get better performance out of your boat? Would you like greater reliability in the engine? Are you hoping to cut fuel consumption? Do you just like the sound and feel of a higher-powered engine? Do you want to increase the boat’s resale value? Are you simply wanting greater peace of mind out on the water?

2. Performance vs fuel use

Boat performance isn’t just a matter of horsepower. Each boat has a minimum and maximum horsepower recommendation, usually found in the manufacturer’s specifications. These restrictions can be caused by the boat’s construction, or the other components. Adding extra horsepower above the maximum doesn’t add much if anything in the way of extra power; it just increases the fuel consumption.

3. Warranty

Repowering the engine on your boat could void any existing warranty that you have on the boat, especially if the new power output is greater than recommended in the manufacturer’s specifications.

4. Insurance

Insurance providers often take horsepower into consideration when pricing a policy. Increasing the horsepower of your boat engine could increase the ongoing cost of insuring the whole boat.

5. Engine weight

The more powerful an engine, the heavier it usually is. A rookie mistake is to place a too-heavy engine on the back of a boat, lowering the freeboard and making it far more likely to ‘porpoise’ – bob up and down even on calm water.

6. Boat features

Hull shape and strength, boat weight, and prop setup all factor into the ideal horsepower rating for your boat’s engine. This sort of calculation is difficult – talk to a professional to get an idea of what sort of performance you could get out of your boat.

7. Boat age

If your boat is old, it could be worth completely replacing the engine and all associated components, like the gear box and stern drive, when you repower it. A new engine will run better on unleaded fuel, and be easier to match parts when they wear out. If you have a newer boat, you could be better off just upgrading the engine and the ancillary parts it needs to run, leaving all other components as they are.

8. Fuel efficiency vs performance vs reliability

What’s your primary goal in repowering your boat? Do you want it running at peak efficiency, using as little fuel as possible? Would you prefer to get maximum performance and speed? Are you mostly interested in ensuring that the engine is running smoothly and reliably? Or would you prefer a balance of all three?

9. Petrol vs diesel

Diesel engines are generally quite a bit cheaper to run than petrol engines. If you use your boat a lot, it can be worth the extra upfront costs to get the ongoing savings of switching to diesel. An average petrol engine package costs around $30k – an equivalent diesel engine package usually costs $45-50k. Be aware, though, that there are extra upfront costs involved in switching to diesel:

  • If the genset currently runs on petrol, you’ll need to replace it with a diesel model. While it is possible to run a petrol genset with a diesel engine, in practice it’s usually a nightmare and not something we recommend trying.
  • The fuel tank will need to be cleaned out and a return line fitted. On most boats this is a fairly simple procedure.
  • The engine beds might need reworking.

10. Recondition vs repower

If engine unreliability or overheating is the main problem that you want to solve, then it might not be necessary to perform a full repower. In some cases, it’s possible to simply replace the engine and keep all the existing ancillaries. Generally this is an option if the boat is still fairly new.


Our trained specialists have years of experience in making these decisions to get the outcomes your desire. Contact us to talk through your options before making any decisions.