Buying a used aircraft engine can save you thousands of dollars, but only if you know what to look for. One small oversight can turn a great deal into a money pit. The engine is the heart of your aircraft, and making the right choice requires careful attention to detail. 

It’s not uncommon to find used aircraft engines sold each year that have undisclosed issues that could affect performance or safety (learn more about protecting yourself when buying an aircraft). 

Understanding what separates a solid investment from a potential disaster starts with knowing exactly what to check.

Key Takeaways

Before purchasing a used aircraft engine, you must verify its complete history through logbooks, confirm the overhaul details, inspect for damage like prop strikes or corrosion, check compression and oil analysis, validate all paperwork matches FAA records, and work with a qualified mechanic to assess the condition of the engine. Always ask detailed questions to ask the seller about maintenance, storage, and why they're selling.

CheckpointWhat to VerifyWhy It Matters
Logbook HistoryComplete records, no gapsProves legal maintenance and reveals problems
Overhaul DocumentationWho did it, when, parts usedConfirms quality and remaining engine life
Physical ConditionCorrosion, leaks, damageShows how well engine was maintained
Compression TestPSI readings per cylinderIndicates internal engine health
Prop Strike HistoryAny sudden stoppage eventsCan cause hidden internal damage
Oil AnalysisMetal particles, contaminationReveals wear and potential failures
Paperwork MatchSerial numbers, yellow tagsEnsures legal sale and authenticity

What Is a Used Aircraft Engine?

A used aircraft engine is any engine that has already been installed and operated in an airplane. These engines come in different conditions. Some have low hours since their last overhaul. Others might be close to needing major work. You'll find them for sale from individual owners, salvage yards, overhaul shops, and aircraft brokers.

Used aircraft engines fall into several categories:

The price varies wildly based on condition, hours since major overhaul (SMOH), and manufacturer. A Lycoming or Continental engine with fresh overhaul might cost $30,000 to $50,000. A high-time engine ready for overhaul might sell for just $5,000 to $15,000 as a core.

Understanding what you're actually buying matters. Some sellers use confusing terms. "Zero time" doesn't always mean new. It often means overhauled. "Rebuilt" and "overhauled" have different meanings under FAA rules. A factory rebuild meets stricter standards than a field overhaul.

When you buy a used engine, you're buying its entire history. Every flight hour, every maintenance action, and every part replacement matters. The log tells this story. Without complete records, you're taking a risk you can't measure. Smart buyers want to see every page of documentation before spending a dime.

Why Careful Checks Matter Before You Buy

Buying an aircraft engine without proper checks is like buying a house without a home inspection. You might get lucky, but you're gambling with serious money. Aircraft engines are complex machines with hundreds of moving parts. When something goes wrong at altitude, you can't just pull over.

Here's why thorough checking protects your investment:

Financial Protection

Safety Concerns

Legal Issues

The aviation industry has seen countless cases of buyers who skipped the pre-buy inspection and regretted it. One buyer purchased what seemed like a great deal on a Lycoming engine, only to find it had been in a prop strike incident. The seller never mentioned it. The engine needed a complete overhaul. The "bargain" cost an extra $35,000.

Another common problem happens when the engine logbook doesn't match the actual engine. Serial numbers might be altered. Yellow tags might be fake. Parts might be substituted. A careful inspection by someone who knows what to look for catches these issues before you hand over money.

Should You Buy New or Used?

The decision to buy new or used depends on your budget, mission, and how much risk you can handle. Both options have clear advantages and drawbacks. Let's break down what each choice really means.

New Engine Benefits

New Engine Drawbacks

Used Engine Benefits

Used Engine Drawbacks

For most owners, the choice comes down to math. If you're looking to buy an engine for a Cessna 172 or similar trainer, a quality used engine with 500-1000 hours SMOH makes sense. You'll save $20,000-$30,000 compared to a new engine. That's enough for several years of flying expenses.

However, if you're building an experimental aircraft or homebuilt project that you plan to keep for decades, new might be smarter. You'll know every hour of its history. You won't inherit someone else's deferred maintenance.

One important factor many buyers miss: consider the purchase of a used engine as part of your total aircraft investment. If you're buying a $50,000 airplane, spending $40,000 on a new engine doesn't make economic sense. But for a $200,000 aircraft, a new engine protects your investment (comparing new vs used aircraft markets provides helpful context for this decision).

13 Things to Inspect Before Purchasing a Pre-Owned Aircraft Engine

1. Complete Logbook History

The engine logbook is your primary source of truth. It should show every hour flown, every oil change, and every maintenance action since the engine was new. Missing pages or gaps in time raise red flags. You want to see continuous entries that make sense.

Check for these specific items in the logs:

Pay attention to who signed the log entries. An FAA-certified mechanic or repair station should have performed all work. Vague entries like "engine serviced" without details suggest poor record-keeping. Meticulous logs show an owner who cared about their airplane.

If the seller says the logs were "lost in a fire" or "stolen," walk away. Engines without logs are nearly worthless. Some sellers claim you can get replacement logs from the FAA, but those only show registration history, not maintenance details.

2. Overhaul Documentation

If the engine was overhauled, you need complete documentation from the overhaul shop. This isn't optional. You want to know exactly what was done, who did it, and what parts were used.

Essential overhaul paperwork includes:

The reputation of the shop matters enormously. Anyone can hang a sign and call themselves an overhaul facility. Look for shops that have been in business for decades and specialize in your engine type. For Lycoming and Continental engines, you want shops that do hundreds of these per year.

Ask the seller for the shop's contact information. Call them directly. Ask about their process, what parts they use, and their warranty terms. A quality shop stands behind their work and will talk to potential buyers. If the shop that did the overhaul won't discuss the engine, that's a warning sign.

3. Time Since Major Overhaul (SMOH)

The hours since major overhaul directly affect the value of the engine and how long before you'll need another overhaul. Most Lycoming engines and Continental models have a recommended TBO (time between overhaul) of 2,000 hours. Some models differ.

Here's what different SMOH numbers mean:

Don't assume low hours mean better. An engine that sits unused deteriorates faster than one run regularly. Corrosion forms inside. Seals dry out. Cam lobes develop rust pitting. An engine with 1,200 hours flown in the last 5 years is healthier than one with 400 hours spread over 20 years.

Check when the engine has been run. Ask for the date of the last run. If it's been sitting for more than 6 months, plan for preservation oil and a thorough inspection before first start. More than 2 years sitting? Budget for new cylinders and other work.

4. Physical Condition and Visual Inspection

Before you spend money on technical inspections, look at the engine yourself. You can spot many problems with your eyes and a flashlight. Even if you're not a mechanic, obvious issues should make you think twice.

Look for these warning signs:

The overall cleanliness tells you something about the previous owner. A clean, well-maintained engine suggests someone who cared. An engine covered in oil, dirt, and grime suggests neglect. Yes, engines get dirty, but there's a difference between normal service dirt and years of ignored leaks.

Check the data plate. Verify the serial number matches the logs. Look at the engine model and confirm it's actually what the seller claims. Some people swap data plates to increase value.

If possible, look inside the oil filler and drain. Use a flashlight and inspection mirror. You want to see clean metal, not sludge, rust, or metal particles. Dark oil is normal. Milky oil suggests water contamination. Sparkly oil means making metal - internal wear that's creating metal particles.

5. Compression Test Results

A differential compression test tells you about the internal condition of the cylinders, valves, and rings. This test is critical and should be performed by an A&P mechanic who knows the procedure.

The test measures how well each cylinder holds pressure. The mechanic pumps air into the cylinder through the spark plug hole and measures how much leaks out. Results are expressed as a ratio, like 72/80. The first number is actual pressure, the second is test pressure.

Acceptable readings:

More important than the number is where the air is leaking. The mechanic listens at different points:

Don't reject an engine just because one cylinder is low. Cylinders can be replaced individually. But if multiple cylinders show low compression, or if readings are inconsistent across the engine, it might need an overhaul soon. Factor this into your offer price.

6. Propeller Strike History

A prop strike or sudden engine stoppage is one of the most serious issues to check. When a propeller hits something while the engine is running, the impact travels through the entire engine. It can damage the crankshaft, bearings, gears, and accessories.

FAA regulations require a complete teardown inspection after any prop strike or sudden stoppage. This isn't optional. The engine must be disassembled and inspected by a qualified shop. Many sellers try to hide this history because the teardown and potential repairs are expensive.

Red flags that suggest unreported prop strike:

Always ask directly: "Has this engine ever experienced a prop strike, sudden stoppage, or been involved in any incident?" Get the answer in writing. If they say yes, verify the teardown was performed and documented. If they say no, do your own research. Check FAA accident databases and insurance claim histories for the aircraft's registration number.

Some sellers claim "we just touched the prop tip on grass during taxi" and didn't do the teardown. This violates FAA rules. The engine should be considered unairworthy until properly inspected. If you buy it, you're inheriting that liability.

7. Oil Analysis History

Oil analysis is like a blood test for your engine. It shows what's wearing inside before problems become catastrophic. A used engine with regular oil analysis reports is worth more than one without any data.

Oil samples are sent to a lab that measures:

Look at the trend, not just one sample. Metal counts should be stable or decreasing. Sudden increases mean something is wearing abnormally. Iron suggests cylinder wear. Aluminum indicates piston wear. Copper and lead point to bearing problems. Chrome suggests ring wear.

If the seller has no oil analysis history, that's not necessarily a deal-breaker for a low-time engine. But for a high-time engine near TBO, the lack of data is concerning. You have no way to know if internal wear is normal or accelerated.

8. Accessory Condition

The engine itself is just part of the system. Accessories like magnetos, starter, alternator, fuel pump, and vacuum pump all add to replacement costs if they're worn out.

Check the condition and time on:

Ask when these items were last serviced or replaced. Get serial numbers and check their logs if possible. A magneto nearing 500 hours means you'll spend $1,000-$1,500 per side soon. A failing alternator is another $800-$1,200. These costs add up quickly.

Some sellers pull accessories off to sell separately, leaving you with just a bare engine. Make sure you know exactly what's included. If you're buying an engine without accessories, factor in $5,000-$10,000 to equip it properly.

9. Airworthiness Directives and Service Bulletin Compliance

Airworthiness Directives (ADs) are mandatory safety fixes issued by the FAA. Every aircraft engine has ADs that must be completed. Some are one-time, others are recurring. If the ADs aren't completed, the engine isn't airworthy.

You need to verify:

For Lycoming engines, common ADs address crankshaft inspection, cylinder inspection, and piston pin plug issues. Continental engines have their own set of critical ADs. Don't assume the seller knows which ADs apply. Do your own research on the FAA website.

Some service bulletins aren't mandatory but are highly recommended. For example, Lycoming has service bulletins about using new Lycoming cylinders instead of rebuilt ones. Following these recommendations increases reliability and resale value.

If you find missing or incomplete AD compliance, you have two choices: negotiate a price reduction to cover the work, or walk away. Never assume you can just "catch up" the ADs later. Some ADs require complete engine disassembly.

10. Documentation Matching

Every part of the engine should have a paper trail. Serial numbers must match. Yellow tags must be genuine. Forms must be signed by authorized people. This verification prevents you from buying stolen parts or unapproved components.

Verify these documents:

If something doesn't match, find out why. Sometimes data plates get replaced due to damage. Sometimes cylinders get swapped from another engine. These changes should be documented. If they're not, you could have unapproved parts.

Check the manual that comes with the engine. It should be the correct model-specific maintenance manual and parts manual. These aren't just helpful - they're legally required documents for maintenance.

11. Storage and Preservation

How the engine was stored between its last run and now matters tremendously. Engines need special care when not in use. Improper storage causes corrosion, stuck valves, and degraded seals.

Ask these questions about storage:

An engine stored in a climate-controlled hangar with proper preservation for 2 years is fine. An engine that sat outside under a tarp for 5 years is probably garbage. Moisture gets inside. Rust forms on the cam lobes and lifters. Corrosion pits the cylinder walls.

If the engine might have been stored improperly, budget for a complete inspection and possible rebuild. Don't trust a salesman who says "it just needs a quick check." Engines don't improve with age and neglect.

12. Price Verification and Market Comparison

Is the asking price fair? You can't know without comparing similar engines. Market values fluctuate based on model, condition, time, and demand.

Research current prices:

A used aircraft engine with 500 SMOH, complete logs, and recent oil analysis is worth significantly more than one with 1,800 hours, gaps in the logs, and no test data. Don't pay mid-time prices for a high-time engine just because the seller is persuasive.

Be especially careful with deals that seem too good to be true. They usually are. If an engine is priced 40% below market, something is wrong. Maybe it has a prop strike history. Maybe the logs are incomplete. Maybe it's stolen. Do extra checking on any bargain-priced engine.

Consider the core price when evaluating high-time engines. A runout engine might sell for $8,000-$12,000 as a core. If someone is asking $20,000 for an engine with 50 hours left until TBO, they're hoping you won't do the math.

13. Professional Pre-Purchase Inspection

After you've done your own checking, hire a professional for a detailed pre-buy inspection. This costs $500-$2,000 depending on depth, but it's the smartest money you'll spend. An experienced mechanic catches problems you'll miss.

A thorough pre-purchase inspection includes:

Choose a mechanic who specializes in your engine type and isn't connected to the seller. Don't use the seller's buddy or someone they recommend. Find your own independent inspector. Look for someone with turbine experience if you're buying a turboprop engine.

The inspector should provide a written report with photos. This becomes part of your engine's documentation and proves you did proper due diligence. If the inspection reveals problems, use the report to negotiate price or walk away entirely.

Never buy sight unseen without a professional inspection. Some buyers purchase engines from online ads or auctions without seeing them in person. This is gambling. Photos don't show compression numbers, internal corrosion, or documentation problems. If you can't inspect it yourself or hire someone local to do it, don't buy it.

Common Mistakes Buyers Should Avoid

Even experienced aircraft owners make mistakes when purchasing a used engine. Learning from others' errors saves you money and frustration. Here are the most common problems buyers encounter:

Mistake #1: Trusting the Seller Completely

The seller wants to sell. Their incentives don't align with yours. Even honest sellers forget details, minimize problems, or simply don't know the engine's complete history. Always verify everything independently. Get answers in writing. Don't accept "I think" or "probably" as sufficient answers.

Mistake #2: Skipping the Pre-Buy Inspection

Some buyers think they can skip the professional inspection to save money. This is like trying to save money by not using a parachute. The inspection fee is tiny compared to the purchase of a used engine. One missed problem can cost ten times what you saved.

Mistake #3: Not Understanding the Difference Between Overhaul Terms

Terms like "overhauled," "rebuilt," "remanufactured," "zero-timed," and "top overhaul" all mean different things. A "top overhaul" only addresses the cylinders, not the bottom end. "Zero-timed" doesn't mean new - it means the clock was reset after work. "Remanufactured" has specific FAA requirements that "overhauled" doesn't. Understand what you're actually buying.

Mistake #4: Ignoring Red Flags

When something seems off, it usually is. Missing log pages, vague answers, pressure to buy quickly, incomplete documentation - these are warning signs. Don't rationalize them away. Don't let enthusiasm override caution. Walk away from questionable deals.

Mistake #5: Not Budgeting for Post-Purchase Costs

The purchase price isn't your total cost. You'll need:

Budget at least $3,000-$5,000 for installation and related expenses beyond the engine purchase price.

Mistake #6: Buying Based on Price Alone

The cheapest engine rarely turns out to be the best deal. A $25,000 engine with perfect logs and 500 SMOH is a better investment than a $15,000 engine with 1,600 hours and missing documentation. Calculate the cost per hour of useful life remaining, not just the purchase price.

Mistake #7: Not Verifying Overhaul Shop Reputation

Some shops do beautiful work. Others cut corners and use inferior parts. Research any overhaul shop before buying an engine they worked on. Check reviews, ask for references, verify they're still in business. An engine overhauled by a shop that went bankrupt or lost their license should raise concerns.

Mistake #8: Accepting Engines from Unknown Sources

Buying from a reputable dealer, established shop, or known aircraft owner is safer than buying from someone with no track record. Scammers exist in aviation just like any industry. An engine advertised online by someone with no verifiable history is risky. If they won't meet in person or allow inspection, they're probably hiding something.

Quick Checklist for Buyers

Use this checklist when evaluating any used engine. Don't skip items even if you're in a hurry. Print this and bring it with you during inspections.

Documentation Review:

Physical Inspection:

Testing:

History Verification:

Financial Considerations:

Professional Help:

This checklist helps you stay organized and thorough. Missing even one item could cost you thousands later. Take your time. Be meticulous. The right engine is worth waiting for.

When you're ready to move forward with a purchase, make sure everything checks out. A good used aircraft engine will serve you reliably for years. A bad one will drain your bank account and keep you grounded. The difference is in the checking you do before you buy.

If you're also considering buying the entire aircraft, make sure to review what to look for when buying a used airplane and check out this comprehensive aircraft purchase checklist to cover all your bases.

Conclusion

Buying a used aircraft engine requires careful attention to detail, thorough documentation review, and professional help. The 13 things to check before buying a used aircraft engine outlined here will help you avoid expensive mistakes and find a reliable powerplant for your airplane. Remember that complete logs, verified overhaul history, and a clean bill of health from a compression test are non-negotiable. Never rush this decision.

Take the time to verify everything, ask hard questions, and walk away from deals that don't feel right. A few extra days of research can save you years of headaches and tens of thousands of dollars in unexpected repairs.

Ready to find the perfect aircraft and engine and fly with confidence? Visit Flying411 for more expert guides, listings, and resources to help you make smart buying decisions in general aviation.

Frequently Asked Questions

How long can an aircraft engine sit without being run?

Aircraft engines should ideally be run at least once every 30 days to prevent internal corrosion and keep seals lubricated. If an engine sits for 6-12 months without preservation, expect some corrosion on cam lobes and cylinder walls. Beyond 2 years of inactivity without proper pickling, you should plan for cylinder replacement and thorough internal inspection before returning to service.

What's the difference between field overhaul and factory overhaul?

A factory overhaul meets stricter tolerances, uses all new parts to factory specifications, and comes with a zero-time designation and warranty. Field overhauls are performed by certified repair stations and typically reuse serviceable parts after inspection. Factory overhauls cost more but offer better warranty protection and often higher resale value. Both are legal and safe when done properly.

Can I install a different engine model than what came with my aircraft?

Installing a different engine requires a Supplemental Type Certificate (STC) or field approval from the FAA. You cannot simply swap engines because they're similar sizes. The installation must be approved with proper documentation, and the aircraft logbooks must reflect the change. Some swaps are common and have existing STCs available, making the process simpler and less expensive.

How do I verify an engine hasn't been stolen?

Check the engine serial number against FAA records and the National Crime Information Center (NCIC) database. Request a title search through aviation title companies. Verify the bill of sale chain shows clear ownership transfer. If buying from a salvage yard, confirm they have proper documentation for how they acquired the engine. Reputable sellers will cooperate fully with verification requests.

What should I do if I find problems during the pre-buy inspection?

Use the inspection findings to renegotiate the price or request repairs before closing. Calculate the cost to fix identified problems and reduce your offer accordingly. For major issues like undisclosed prop strikes or missing ADs, consider walking away entirely. Some problems aren't worth inheriting regardless of price adjustments. Always get repair estimates from qualified shops before renegotiating.