How to do a compression test on an inboard boat motor

That test would not only identify leakage but you could actually identify the location of the leakage. Check power-trim fluid levels.

With the engine warm crank the engine through two or three revolutions.

How to do a compression test on an inboard boat motor. A leak down test would actually be the most accurate. That test would not only identify leakage but you could actually identify the location of the leakage. 1 intake vales - hissing in the intake 2 exhaust valves - hissing in the exhaust 3 piston rings -.

How to Compression Test an Outboard Motor BoatUS - YouTube. Using Air to Test Engines Combustion Chamber. If a low cylinder is found during the compression test the use of air pressure can help you find out if the engine has a valve or piston problem.

Open throttle plates completely. With spark plugs still removed rotate the engine until number 1 piston is at TDC on the compression stroke. What is a compression test.

It is a reading of an engines ability to compress the fuel and air charge in the cylinder with a piston. It is measured by inserting a fitting into the spark plugs threaded hole in the engine cylinder head cranking the engine over through multiple rotations and reading the pressure measurement on a gauge attached by a hose. Also be aware that this engine runs like a Swiss Watch.

There is no way to test compression in a running motor and its likely the difference you would see would be much smaller. With these tests your really looking for a number that is wayyyy off indicating damage other than normal wear. A loose motor often is faster but may lack some low end.

Pull the safety lanyard crank your engine and when the oil pressure comes up the engine will fire when you let the key go from the START position then it will stop running. How to run inboard engine out of the water on a hose - YouTube. How To Compression Test an Outboard Motor - YouTube.

For a compression test the engine itself provides the pressurization. For each cylinder remove the spark plug and screw in the fitting that the gauge connects to. With the coils disconnected so the engine doesnt start crank the engine for about 10 seconds.

The gauge on the tester will register at the highest indicated compression reading. One of the best ways to check your engine is by checking your engines cranking compression because it will reveal a lot of information about your engine. This compression check that is performed is going to tell you if your piston rings are working properly and that your cylinders are in good shape as well.

Inboard marine engines have a different vulnerability as these often have their cooling water mixed with the exhaust gases in the header to quiet the engine. Rusted out exhaust headers or lengthy periods of turning the starter can cause water to build up in the exhaust line to the point it back-flows through the exhaust manifold and fills the. Types of Compression Tests.

There are two basic ways to compression test an outboard. The first is called a leak down test. This uses a special set of gauges.

To perform a leak down test you would pressurize the cylinder with compressed air. One gauge will tell you the pressure of. I didnt realize that Im supposed to test the rings using regular motor oil when doing a compression I used WD40 instead Cyl 4 jumped to 110 and 3 went to 110 also none of the other changed when using WD40.

I will have to re-check with an oil squirter. Bill works from long check lists developed from a body of experience that has been refined over almost three decades of inspections. Compression additional costs may apply Cylinder Wall Condition if visible.

Crank Case Oil Condition and Level. This will allow you to turn the engine over to get the results from the compression test. Another way is to have someone turn the key over again depending on what kind of engine you are doing this on.

You will need to be careful because some engines have features that will continue turning the engine over. Engine oil should be a clean amber or gold color. Black oil indicates old and dirty oil.

If the oil looks milky or frothy its contaminated by water bring the engine in for service. Check power-trim fluid levels. Inspect trim-pump reservoir caps.

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 andor fuel injection and start nearly instantly.

Compression can be tested in two ways. The first method I use involves using a manual handheld compression gauge. I will always run the marine engine up to operating temperature before beginning the compression test to ensure that the oil has been warmed up.

A cold engine never ever tests correctly. Consult the engines service manual to find out exactly what an engines compression should be. Generally its about 150 pounds per cylinder.

To run this test remove all of the spark plugs and fully open the throttle. With the engine warm crank the engine through two or three revolutions.