Mercury 4 Stroke Compression Test

Juni 12, 2021 Posting Komentar

You are seeing 105 psig vs a theoretically perfect 118 psig or a difference of less than 15 from perfect. As for the compression test it is a diagnostic tool.

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Merc called and said they would give him a 2003 90-HP he said you just put a new 2003 powerhead on and it did the same as the others plus after a leakdown test two of the cylinders have grooves that are 0035-inch deep and 20 less compression then the other cylinders.

Mercury 4 stroke compression test. I know that the factory service manual doesnt mention numbers. The compression test should be done with both plugs out of the motor and the plug wires grounded out to the block. But its also the cheapest and easiest to assess and if necessary repair.

The most likely issue with that cylinder is the injectors are clogged and the engine or at least that cylinder is running lean. Here is everything that you need to know about outboard compression tests. Results vary depending on whether the outboard is a Four-Stroke or a Two-Stroke.

This cranking with the ignition disabled will also prime the fresh oil around the block reducing friction at startup after the service. A wet compression test will temporarily seal the piston rings and possibly raise the compression. Re run compression tests.

Most are around 120. After the oil has been applied retest that cylinder. Results vary depending on whether the outboard is a Four-Stroke or a Two-Stroke.

Check all six cylinders for compression at cranking speed. As the tested cylinder comes up on its compression stroke. Pull all six plugs keeping them in order.

Good results for Four-Strokes should be 180-210 PSI and Two-Strokes should be around 110-130 PSI. It is used to help determine why an engine is NOT running well not to predict if it will. Damaged or blown head gasket.

I understand that the compression will also increase when tested on a warm motor. Compression checks can be used to let you know about how well the outboard engine is working. The guy said he has a friend that could come by his house and the compression check for 30.

To perform this test at home you will either need a remote starter button or a friend who can turn the ignition key with the kill lanyard removed. Using Air to Test Engines Combustion Chamber. Also Know how much compression should a 125 2 stroke have.

When it comes to How to test outboard motor compression it is important to know about the four phases that are distinct in a 4-stroke cycle. They are asking 12k for the boat. To use it as a indication of a engines longevity is a bit like listening to your breathing to predict your overall health.

Manually open the stat pushing against the spring and insert a sewing thread. Note how fast the compression increases and write down the highest reading. You can test it on the stove in a pan of water with a candy thermometer.

Repeat testing for all cylinders and compare results. Good results for Four-Strokes should be 180-210 PSI and Two-Strokes should be around 110-130 PSI. I plan to check and adjust valve lash as needed prior to my next compression test this alone may help that 182 cylinder.

A compression test is still the best test for a 2-Stroke engine and should be performed. This would usually lead to zero compression on that cylinder. And the one at one at 75-80 PSI indicates there is likely an issue going on with that cylinder.

The prop removed and the throttle in the FWD wide open position so the cylinders get plenty of air to compress. We used to run ATF at about 25 but that took forever. You are a little on the low side at 90 PSI.

With spark plugs still removed rotate the engine until number 1 piston is at TDC on the compression stroke. Posted 11-03-2008 0725 PM ET US Low compression in one cylinder is generally caused by one of three things. HOW TO PERFORM 100-HOUR SERVICE ON A 4-STROKE MERCURY OUTBOARD This cranking with the ignition disabled will also prime the fresh oil around the block reducing friction at startup after the service.

You will be able to hear the cranking speed slow. Higher than that I would visually inspect the cylinders. Compression Test on Mercury Outboard 150 hpBy FarhadFKCamera - YouTube.

The Mercury 25 HP 4 stroke outboard motor model delivers constant easy starting crisp throttle response maximized fuel economy and overall outstanding performance. Though this advanced compact Mercury outboard motor offers EFI that no other outboard or boat manufacturer offers at this horsepower rating often users experience some troubleshooting issues while using it. Here is the goofy part to mercury service manuals.

They should be within 10 of each other. 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. Holding the thread with the entire stat in the water when it starts opening it will drop from the thread.

Inspect for pattern as outlined above. Looking at getting an 08 Tracker 190 with a Mercury Optimax 90hp motor on it with 300hrs. Hereof how much compression should a 4 stroke outboard have.

A compression reading around 200 is something you might see in a diesel engine but not in a normally-aspirated 4-stroke gas engine designed for 87 octane fuel. It does not predict how well an engine will run or how long it will live. The pull rope should be very easy to pull when done this way.

If the cylinder compression pressure increases the piston rings are sticking. What Outboard Compression Test Results Mean. Test all cylinders the same way with the same number of.

Leak down test are only viable options on 4 stroke engines and compression test are no longer even recommend on 4 Stroke Outboards by Yamaha or Mercury. Merc says no so he is now involved with a lawyer who is suing Merc. Im going to be running it at least once a season on all of our 2 cycles and probably our 4 cycles as well at least the carbuerated ones.

Im getting jumps of 25 to 40 and I think the stuff is miracle juice. I have been told that Mercury doesnt publish compression numbers. So at 190psi it is within acceptable range and indicates a strong engine with no blow by.

Im guessing youll go to 125 to 130. Open throttle plates completely. Repeat testing for all cylinders and compare results.

First of all connect the tester to a cylinder and turn the engine over 6 to 8 compression strokes. HI Mercury states acceptable pressure as between 135-210psi as long as the lowest cylinder pressure reading is at least 75 of the highest pressure reading. The Seloc book give a few random numbers that are not set in stone and the lowest is a 45 HP at 90 psi.

At least I cannot find them the manual is disorganized somewhat. Readings will vary from gauge to gauge so the test is more about measuring the. Obtain a can of fogging oil and spray the perimeter of the cylinder walls and pistons.

The spec page says compression COLD yet the compression check procedure page says warm the.

Compression Test On Mercury Outboard 150 Hp By Farhad Fkcamera Youtube