One of the most important part of the vessel is the outboard motor, of course. Low compression in one cylinder is generally caused by one of three things: 1. As the outboard "ages", the cylinders become out of … Responsible for compressing the air-fuel mixture, then forcing it from the exhaust, the piston can overheat and suffer catastrophic damage from a number of reasons. We all know that while on the run, the outboard motor can go wrong in many different ways. A timing belt is designed to last between 60,000 and 100,000 miles. It's either fucked head gasket, valves, rings or piston, or the block could be cracked. The process is necessary for the car to move and function. I replaced all the spark plugs, tested coils all tested good, but when I did a compression test there was no compression on the #3 Cylinder. If the psi leaks Dan, From the mid-late 80's or thereabouts outboards were lowered in compression to around 120psi in order to cope with the newly introduced Unleaded fuel at typically 89-91 RON (Research Octane Numbers) as … It can cause misfires and reduce power. cylinder 2 has no compression due to the valve spring not shutting. Re: No compression in one cylinder (acatli) Nope not hard at all if you use BRP wrist pin bearings they will stay together when you put them in to the connecting rod. Also, at low RPM (i.e. Repeat the process one-by-one for each cylinder. The engine will start right up but with This would usually lead to zero compression on that cylinder. With that much variance between cylinders, we can tell something is wrong, and we're going to have to dig deeper to understand why our engine is down on compression. What happened? If no compression is present in any one cylinder it means a mechanical malfunction has occurred while low compression could just be the sign of worn internal engine parts. Got home did a compression test top cylinder is barely 50 lower is around 80. A low compression in one cylinder can compromise the performance of the engine. Motor runs fine. “No compression” would indicate “zero” psi and that is unlikely unless the piston has the top blown out or one of the valves is held open significantly. Go to the key and turn the engine over for 3 to 5 seconds. In my opinion I would be careful on how hard you run the motor.I just had my outboard overhauled due to low compression on one cylinder. One of the major engine failures of an outboard motor concerns the temperature and operation of the piston. What I do before assembly is to use the piece of cardboard that comes attached to the bearings lay it on the bench. compression on johnson outboard motor? Our six cylinders gave us the following readings: 170, 170, 140, 190, 160, and 130. If the valve spring is broke it can be replaced without removing the cylinder head. This all depends on why it has low compression. There are many different low compression symptoms which will cause the engine to run abnormally. How to fix low compression in number one cylinder of a mercury 70el engine - Answered by a verified Marine Mechanic We use cookies to give you the best possible experience on our website. It doesn’t matter whether you turn it over for 3 or 5 seconds. No compression at all doesn't strike me as something that seafoam will fix. Screw the end of the compression gauge into one cylinder. The compression in the internal combustion (IC) engine cylinders takes place when air and gas get mixed together. In some cases This uses a special set of gauges. Loosening the rockers to release the valves and then connecting air pressure to an adapter at the spark plug opening should isolate the cause of the leak. The first is called a leak down test. No worries on the one low cylinder, it is within the 20% rule. What Outboard Compression Test Results Mean. The others are still 125. There are many different low compression symptoms which will cause the engine to run abnormally. To perform a leak down test, you would pressurize the cylinder with compressed air. The result is either a stalled system or an inefficient one where the crankshaft doesn’t push the piston far enough so only a little compression is created in the cylinder. The labor guide shows 8 hours labor to replace the valve springs or valve seals on one bank, they may charge less to replace just one … Look at the high psi reading on the gauge and let the gauge sit for 5 minutes. If there’s low compression in one cylinder, you will face many problems including misfiring at the time of starting the car or weak engine performance. Re: Evinrude 150 (low compression on 1 cylinder) Only remove the bypass cover for the one cylinder that has a low reading. Just be nice to it and check it twice a year to make sure it stays consistent. Low compression in one cylinder can I hone it? If you have one low cylinder on a v6/v4 you have another problem as the rods and pistons beng the same part have far less chance of being different. when starting the motor) you can assume ambient pressure in the cylinder when it covers the exhaust opening, and the compression relies on the tightness of the piston ring, the head gasket, and the spark Poor compression in an outboard results from cylinder pressure leakage usually around the cylinder rings. My re-manufactured outboard motor lost compression in the number 3 piston only after an hour of use. If … In this case, learning all about the common problems as Our mechanic (whom I trust) was hoping it was just a sensor since one of them was full of carbon but today he ran a compression test and found that the number 4 cylinder is shot and has no compression. There is no need to unscrew the water cover on the cylinder head, just the 14 cylinder head bolts. I have never done a leak down test on a 2 stroke. The first one is that if your car is running for a while with misfires, the fuel might wash the cylinder walls, which causes low compression. Results vary depending on whether the outboard is a Four-Stroke or a Two-Stroke. By continuing to use this site you consent to the use of cookies on your device as described in our cookie policy unless you have disabled them. You can run a compression test on a cylinder by inserting a gauge in the spark plug cylinder and turning the engine over several times. 02-06-2017, 08:26 PM Traded for a 1986 dt25 Suzuki outboard. An engine with low compression in one cylinder will present itself by having a misfire and running rough while no compression in all cylinders will cause the engine not to start. If one of the valves is bad, re grinding it or replacing them is the fix. This video shows the process of checking the compression on you boats outdoor motor. The piston may have failed due to: Improper fuel/oil mixture (2stroke) Poor quality fuel which Cylinder compression doesn't actually start in a two-stroke until the exhaust port has totally closed, so even with crankcase compression the true ratio is somewhat less than the nominal one, especially at the revs attained at Checking compression is done using a simple compression gauge and can be … Hey man, I did a compression test today on my 2000 Mercury Optimax 200hp with the throttle wide open, warm engine, and a remote start switch. Damaged or blown head gasket. Low compression in 1 cylinder 05-29-2018, 08:16 AM I have a 2001 LX250TXRZ with 120psi on al cylinders except bottom on port side which is 65psi. I got a johnson v6 200 horse outboard motor and i did a compression test on it and all cylinders were reading about 80 psi, is that good for that type of boat motor? Here is how to fix low compression. If your not sure what the compression specifications were when the motor was new, refer to Back home I compression tested the old girl and the top cylinder compression is only 30psi. One gauge If no compression is present in any one cylinder it means a mechanical malfunction has occurred while low compression could just be the sign of worn internal engine parts. There are many symptoms to look out for with a misfiring outboard, from unusual popping and sputtering sounds, to a strong smell of gas/petrol, to excessive vibration as a result of the uneven movement of components in the engine. The second reason is that the piston rings are sealing poorly or were stuck. There are two basic ways to compression test an outboard. Good results for Four-Strokes should be 180-210 PSI, and Two-Strokes should be around 110 I guess it's now a question of is it worthwhile rebuilding an old engine like this or should we just reopen the boat The difference was 125 psi on all 5 cylinders and #6 was at 100 psi. All The other cylinders were right at 120 psi dry test. I feel like maybe valves are the most likely, given its only one cylinder and you're reporting no compression, of course it could be any of em. Re: OUtboard Cylinder Compression? If the rings are worn out, the motor should be rebuilt. They can also cause engine misfire, which is essentially when one or more cylinder fails to fire as it should due to a faulty spark plug. If your motor only has one cylinder, a difference or drop of 15 psi as compared to when the motor was new is also a reason for concern.