MERCURY 100 hp 4-stroke EFI long shaft power trim good condition

Mercury 100 HP 4-Stroke EFI is widely regarded as a reliable, high-performance mid-range outboard, favored for its power-to-weight ratio and fuel efficiency.

Because you are interested in a used unit, do not rely on the seller’s claim of “good condition.” Here is the breakdown of the engine and a checklist to help you verify it before purchase.

Mercury 100 HP 4-Stroke Specifications

• Engine Type: 2.1L, 4-cylinder, 8-valve, Inline 4-cylinder (SOHC).

• Induction: Multi-Port Electronic Fuel Injection (EFI).

• Shaft Length: Available in 20″ (Long) or 25″ (Extra Long).

• Trim/Tilt: Power Trim and Tilt is standard.

• Weight: Approximately 163 kg (360 lbs) for the lightest model.

• Key Tech: Includes SmartCraft Engine Guardian (which alerts you to engine problems) and is generally known for smooth, quiet operation.

Used Outboard Inspection Checklist

If you are evaluating this for your inventory or a client, perform these checks:

1. Compression Test (Mandatory): This is the single most important test for internal engine health. All cylinders should show balanced pressure; significant variance is a red flag for internal wear.

2. Gearbox/Lower Unit Oil: Drain a small amount of gear lube.

   • Milky/Cloudy: Indicates water intrusion (failed seals).

   • Metallic Shavings: Indicates internal gear or bearing damage.

3. Trim & Tilt Unit: * Cycle it up and down. It should be smooth, quiet, and must not “bleed down” (slowly drop) when left in the full-up position.

   • Check the trim rods for leaking hydraulic fluid.

4. Engine Oil: Check the dipstick. The oil should be clean and translucent. If it smells burnt or is pitch black, it may indicate neglected maintenance.

5. Cooling System: When running the engine (in a test tank or on muffs), ensure there is a strong, consistent “tell-tale” (water stream). If it is weak, the impeller likely needs immediate replacement.

6. Service History: Ask for receipts or contact the mechanic who performed the service. Regular oil/filter changes and impeller replacements are the best indicators of a motor’s longevity, often more important than the raw number of hours on the clock.

7. Test Run: Always try to see the engine running. Listen for abnormal knocks, vibrations, or erratic idling.

Business Considerations

• Command Thrust (CT) vs. Standard: Determine if the unit is a “Command Thrust” model. CT models have a larger, heavy-duty gearcase designed for heavier loads (like pontoons or workboats). These require different propellers and are not interchangeable with standard gearcases.

• Rigging: If you are buying this for Buy Mustang parts Ltd, ensure the package includes the rigging kit (control box, cables, gauges). Buying these separately can significantly increase the cost.

• Serial Number: Always get the serial number from the engine plate. You can use this to verify the exact model year and check for any outstanding factory recalls or warranty status with an authorized Mercury dealer.