How do you do a compression test on an outboard engine?

Question

How do you do a compression test on an outboard engine?

also is their a book I can buy that will tell me how to maintain an outboard engine and fix it myself and what not?

Answer 1

Strm chsr07 is right, except you can take out all the spark plugs.  Oil is not going to shoot out of the holes.  However you may get a light mist of some fuel and oil, no big deal it will not make a mess.  You should activate the kill switch though.  Or use a starter buttom directly on the starter solenoid and you will not have to worry about the kill switch.  To do this connect 1 lead of the button to the positive terminal on the solenoid and connect the other lead to the terminal which the yellow/red wire is connected.

I have done compression tests hundreds of times as I work at a boat store.  Also you can get a service manual for your outboard, but why attempt repairs yourself.  I cannot tell you how many times I have worked on an outboard which the owner attempted to repair themselves.

Answer 2

You need to buy a compression tester.

When you get it the first step is to disconnect the spark plug wires from the spark plugs. Then s***w in the tester one spark plug at a time and turn the motor over each time until the gauge reaches its maximum pressure. Have someone read the gauge.

The pressure within each cylinder should read within 3 to 5 pounds of each other. Do this on each individual spark plug.

I have seen many testers at reasonable prices on Ebay. Good Luck!

EDIT: Don't take all the spark plugs out at once. Just the spark plug wires! Only take out one spark plug, to be replaced by the compression tester.

Answer 3

You can buy outboard repair manuals on eBay or at most boat dealers, or boat part places on the internet.

To do the compression test: there are several types of compression testers on the market. If you buy one, read the directions with it as to how it goes in a spark plug hole. Some s***w in, some you just hold in tightly. If you borrow one, ask the owner to make sure. You must remove all of the spark plugs to do the test. The best thing to do is turn the engine over by getting a remote starter switch from the car parts place. It has 2 alligator clips that you connect to the starter solenoid and a button you push to crank the engine. Cost about $12. The reason for this is if you crank it with the key, you are allowing electricity to get to the plug wires and they can spark and ignite the gas mixture that will be blown from the plug holes. Leave the key in the off position, while doing this test.

Attach the compression tester in the proper manner and crank the engine at least five full revolutions. As others have said you should not have more than 5 lbs pressure difference between cylinders.

The repair manual will give you an acceptable compression number for the engine.

Answer 4

Remove all plugs. Open throttle wide. Do compression test.Keep rag handy to wipe any oil or gas. PS. Dont smoke while doing op A!!

Answer 5

Buy a compression tester at your local auto parts store ,take out one spark plug, s***w the thing in thiere, turn it over, and repeat for each cylinder.   If it is a 4 stroke oil cant get everyere, and if it is a two stroke, and oil does get everywere it is running two rich.

Answer 6

To perform a compression test on a outboard engine, you need a compression tester, available at most auto parts stores. Also, you may find them at a place where outboards are sold and serviced. Now, as to the actual compression testing... Once you have a compression tester, you need to remove the spark plug or plugs, depending on how many cylinders your outboard engine has. For a single, after you have removed the plug, s***w the end of the compression tester into the plug hole... Then, turn over your motor once, and note your compression reading. Usually, if the reading is at least half, you have decent compression. You do it the same for a engine, with two plugs, except, that you have to check each cylinder seperately, noting the reading, as before.  Yes, there is a book you can buy that will tell you how to maintain an outboard engine, and, fix it yourself. In fact, I have the one of the books, but, I am not sure, at the moment, as to where it is, exactly. But, at any rate, you should be able to go to any place where they service and sell outboards, and accesseries. You should also be able to go to a bookstore, and either special-order it, or, they may have them on hand, as well. I have seen them in bookstores, though, I think your best bet would be the outboard business, where they sell them.