How to Check Used Inboard Boat Motors

How to Check Used Inboard Boat Motors

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When considering buying a boat, whether to purchase a new or used model is always a difficult decision. Buying new assures a certain degree of reliability and usually a dealer or manufacturer's warrantee. Buying used means you can get a bigger boat with more features for the same amount of money. Examining the hull and interior of a used boat is a relatively straight-forward procedure. Look for dings, scratches or obvious repairs. Examining the engine of a used boat is not so simple.

Items you will need

  • Flashlight

  • Multimeter

Owner and Records

Ask the current owner how the motor has been maintained and who did the maintenance. A self-maintained motor isn't necessarily bad but there may be no service records. A dealer-maintained motor leaves a paper trail both with the owner and at the dealer. Check the records if available.

Ask about any non-routine repairs which have been done to the motor. Changing a water pump, alternator, starters and the like isn't necessarily a deal breaker, but those things don't usually go bad on motors with low hours.

Ask why the boat is for sale. You may get the honest answer, you may get outright lies or something in-between. You will also get a feel for how forthright the boat's owner is being with you.

Visual Inspection

Look at the general appearance of the motor and the engine compartment. Is it clean and tidy or dirty? Does it have oil and moldy bilge-water underneath?

Look at the overall appearance of the boat. Chances are good a boat which is dirty and ill-kept has not had the motor maintained faithfully. Don't mistake normal wear and tear for poor maintenance.

Check the oil level in the engine with the dipstick. Is it up to full, dirty, recently changed? Be especially skeptical of a motor which is low on oil. Modern-day motors with a modicum of care don't become oil burners.

Examine the belts and hoses for tightness and weathering. A weather-checked belt or hose doesn't mean the motor is no good, but may point to repairs you will need to do sooner than later if you close the deal.

Check the paint on all exposed nuts, bolts and connections. Marine motors are completely assembled before they are painted. If the paint has been chipped away on the alternator bracket, valve covers or other places, it's a sign mechanical work has been done.

Examine the motor mounts where the engine attaches to the hull of the boat. This is a weak point in many boats. If they are cracked or show signs of any lack of structural integrity, an expensive repair will be required.

Check the hours on the engine hour meter. A well maintained engine will last thousands of hours with little internal wear. A poorly maintained engine can fail with a few hundred hours of service. Most "weekend" boaters put less than 100 hours on their boat in a year.

Start and Run

Put the boat in the water or attach a garden hose motor adaptor to the lower unit so the motor can be started.

Turn the key and consider how quickly the motor starts. Most inboard engines these days are equipped with electronic ignition systems and/or fuel injection and start nearly instantly.

Listen to how the engine sounds. It won't sound exactly like an automobile engine, but there should be no grinding, clatter or other unusual sounds.

Test the alternator output with a multi-meter. It should show slightly more than 14 volts on the meter.

Check all hoses and the motor in general for leaks.


  • Shy away from, or at least don't pay top dollar for, boats which are going through their third or more owner.


  • The seller is trying to get the most for his used boat. You are trying to get a bargain. There's nothing in the above warnings which can't be repaired, but they are bargaining chips. Offer a couple hundred dollars less for old belts and hoses to $2000 or more discount for low oil or obvious misrepresentations.
  • On the other hand, if a boat's motor has records of being well maintained, looks good, starts easily and sounds good, chances are you are in for years of trouble-free boating.
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