Many owners contemplate the pros and cons of upgrading to a higher horsepower engine for their airplane. Does it really make sense to do so? Do the actual gains outweigh the time and expense? What are the unforeseen costs of such an endeavor? Will you end up with a white elephant?

We can tell you up front that this is more of an individualized decision than it has ever been. It's specific to airplane types and models in terms of how successful and sensible such a procedure is but, just as important, how the airplane is used. Some upgrades are more sensible than others. Some are not only financially unwise, but also almost impossible to sell later on. They also may have chronic overheating issues or appalling fuel economy, especially with the limited fuel tank size available in some older airframes

In the November issue of Light Plane Maintenance, you can find this story of one of the better engine upgrade choices in terms of both performance improvements as well as enhanced value. Of the popular engine upgrades there are even a few cases of multiple competing STCs from which to choose.

Will you need a new prop, and how does the STC process work—you can't just plop an engine of any type and horsepower into a certified airplane. You must find an approved Supplemental Type Certificate for your airplane where someone has done the engineering and obtained FAA approval for this engine swap and purchase that certificate. Otherwise, you'll need to go the potentially wildly costly, one-off route and seek field approval locally. These are generally money pits and to be avoided.

There's more to an engine upgrade than just the numbers. Are you doing it as a project—sort of a hot-rod hobby? If so, to what degree can do you want to be involved in the process? Does it make any sense at all to actually buy and install a used higher horsepower engine to hold the costs down? The answer is absolutely yes, but given the costs, some careful analysis is a must.

In this article, a long-time owner of an older Bonanza did just that—successfully installing a used higher horsepower engine at a reasonable cost. He did much of the work himself, but is not a mechanic—he did it under the supervision of a certified mechanic. Not only did he do it once, but three times over the course of many years as desirable engines became available on the used market. If you are interested in an engine upgrade on a budget, don't miss this article.

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