Engine Surveys by Stateline Marine Surveyors, James T. Seith, SAMS® AMS® , Winthrop Harbor, Illinois, USA Stateline Marine Surveyors
Winthrop Harbor, Illinois, USA
Serving Illinois, Indiana, Michigan and Wisconsin

James T. Seith, SAMS® AMS®

25 unbroken years in the Marine Industry
Principal Marine Surveyor
Structural and Mechanical Surveys. Don't just get half a Survey!

Engine Mechanical Inspection (Engine Survey)

Marine Surveys by Stateline Marine Surveyors, James T. Seith, SAMS® AMS® , Winthrop Harbor, Illinois, USA An engine mechanical inspection includes removal and inspection of the spark plugs. Many different abnormal running conditions can be observed from the spark plugs alone, and can tell you how each individual cylinder is firing. I do install new spark plugs while the old ones are out, saving you from doing this for the next two years or 100 hours. You can also start a preventive maintenance record knowing that the spark plugs are new. Fuel filters, distributors, and rotors are not replaced or inspected. This is the easiest and cheapest part of the tune-up.

A full compression test is also conducted. The compression test consists of measuring cylinder pressure at cranking speed. The test results can help determine the condition of the pistons, rings, valves, and gaskets. This is a highly recommended procedure when purchasing a used vessel.

The importance of a compression test is to determine variations in compression between cylinders. Compression is considered normal if the lowest reading is 90% or more of the highest reading. (Highest reading x .90 = acceptable low).

  • Normal compression increases evenly and quickly from start to end of test on each cylinder.
  • If compression is low on the first stroke, builds up on the following strokes, but does not reach normal, leaking piston rings are indicated.
  • If compression low on first stroke and does not build up on following strokes, leaking valves are indicated. You can recheck cylinders with low compression by squirting oil into the cylinders through the spark plug hole (approx 3 squirts from a plunger type oiler) and retesting.
  • If compression improves, a ring problem is indicated.
  • If compression does not increase, a valve problem is indicated.
  • Low readings from two adjacent cylinders may indicate a leaky head gasket between cylinders.
  • An engine that exhibits slightly higher readings than the manufactures specifications could indicated excessive carbon deposits in the combustion chamber or on the piston.
While the spark plugs are out, a bore-scope is inserted into each of the combustion chambers. I can see the top of the piston, the cylinder walls, and with a special attachment I can see back up at the valves.

If the motor(s) or are fuel injected, I download all available information available from the motor(s) ECU (Electronic Control Unit). This will produce a 1-7 page report that normally shows current trouble codes, actual engine hours on the ECU, and the engine(s) run times are broken up into 5 RPM (Revolutions Per Minute) categories. This way you can see how the vessel has been driven. For example tournament bass boats, idle and wide open throttle, that's it!

The only way to truly inspect a motor is complete disassembly. This is not recommended or cost effective for the normal everyday boater. A mechanical inspection is very useful tool in determining an engines overall condition.

Engine Inspection Average Cost: $175.00 + $5.00 each spark plug (V-8 $200.00 + $40.0 in plugs = $240.00 each engine).
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Click here for A Sample Engine Computer Readout. (PDF)
Boats don't always tell you what's wrong, get a mechanical inspection of the engine and all of its components. engine surveys
spark plug info
We regularly perform marine surveys in the following locations: Wisconsin: Green Bay , Sister Bay, Egg Harbor, Sturgeon Bay, Milwaukee, Racine, Mt Pleasant, Kenosha, Winthrop Harbor, Lake Geneva. Illinois: Winthrop Harbor, The Chain of lakes, Antioch, McHenry, Fox Lake, Waukegan, Chicago. Indiana; Gary, Michigan City, Benton Harbor, Grand Haven.

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Copyright © 2008/2020 Stateline Marine Surveyors, Winthrop Harbor, Illinois, USA, jseith@charter.net
Installed September 14, 2008, Last Revised August 28, 2020 - Hosted and maintained by Don Robertson