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When is it best to repair a marine engine and when would it be better to replace it? There is no simple answer here, but rather pros and cons to consider.

Our reason for writing this is we have seen many boaters spend more money rebuilding old engines than it would have cost to replace them with new ones. This does not mean we believe you should replace your engine every time something goes wrong. Up to a point, repair is the way to go, but there comes a time when it is better to replace. We believe you should objectively consider the following and use that as a basis for making a rational decision. 

– How badly damaged is the engine? Low compression due to wear is a relatively straightforward rebuild, while an engine that will not turn or one that sat with water in it is much more likely to be problematic.

– How old is the engine? Generally, engines less than 10 years old have readily available parts. The older they get, the more expensive and harder to find the parts are.

-Do you have a single-engine or multi-engine application? If you have more than one, then repowering might be less of an option because a new replacement to match the good engine may not be available.

Rebuild Cons:
– It takes way longer to get through the rebuild process than it does to repower.
– Your rebuilt engine may be like new on the inside but will still have worn out or corroded parts bolted to it.
– The rebuilder may offer a warranty on their work, but it will not cover the cost to remove and reinstall the engine if it fails, and will not cover failure of the engine if the cause was a part bolted to it or a problem with the installation.
– Older design engines are less efficient and have lower power to weight ratios.

Repower Pros:
– Get back on the water much quicker.
– Mercury new and remanufactured engines come with a factory warranty that includes labor coverage.
– In most cases, new and remanufactured engines come complete and ready to install, there are no old parts being re-installed on the engine.
-New engines are more efficient and have higher power to weight ratios, so your fuel bills go down and your speeds go up.


Apples to Oranges:

– It is easy to estimate the cost to supply and install a new or remanufactured engine. It is impossible to accurately estimate the cost to rebuild an older engine. How do you know what parts will have to be replaced until you take them off, clean them up, and inspect them? Too often we have met people who started a rebuild project based on an estimate of $3000, and now they have spent $10,000 and lost 6 months downtime and it is still not done. Finally, do not even consider automotive engines for use in your boat. They may look similar, but they are not. An automotive engine in a marine application will fail, and it will fail sooner rather than later.