advice on suzuki outboard - Page 2

John R · #11 06-25-2003, 09:34 AM

What do you guys consider the best methods for determining compression readings? 2 Strokes being a lot different from 4s, do you:

Spray some oil into each cylinder before taking test?
Test Cold, Test Hot, Test both?
Test under power?

Thanks...

Briguy · #12 06-25-2003, 11:22 AM

John,

I have always tested cold and have never tested hot. Since the piston and rings expand you may get a higher number when hot. In any case, I would never test a motor while under a load.

Jon G · #13 06-25-2003, 06:24 PM

John this came straight from a mechanic I work with. I tested my Merc [img]images/icons/frown.gif[/img] yesterday(Getting new Suzuki next week [img]images/icons/smile.gif[/img] ). Warm engine up then remove all spark plugs set the throttle to full open and then test one cylinder at a time. I was told if you find a cylinder that is low you can spray some oil in and try it again. If the reading goes up you have a ring problem( as the oil helps seal the rings temporarily) if it stays the same you have some other problem causing the loss (cracked piston, head gasket etc.)

John R · #14 06-26-2003, 11:18 AM

Thanks! Any other recommendations from the peanut gallery [img]images/icons/rolleyes.gif[/img] [img]images/icons/grin.gif[/img]

barnacle · #15 06-26-2003, 08:05 PM

Have a leak down test done on the engine. These test are much better then a compression test.You do want to compression test the engine when it is warm. Also you want to compare the readings from bank to bank.

Reel Smoker · #16 06-26-2003, 09:40 PM

Joe, whats going on with Bombardier are they selling out? Any new changes that you might know off.Thanks

John R · #17 06-26-2003, 10:32 PM

How do you do the leakdown test & what tool would you use?

Joe - remember what good compression readings are for a 83 235 ??

JAL · #18 06-27-2003, 01:12 AM

Spraying oil into the cylinders is an old "mechanics trick" which helps the rings seal to improve the results on a compression check. For a true reading, don't do it. Also, allowing the engine to run will help rings seal, especially on two-strokes which burn a mixture of oil and gas.

For the most accurate test, check an engine that has not been run. I have always been slightly suspicious when checking out used outboards or boats when the owner has "warmed up" the motor just prior to my arrival.

There are two types of compression tests- one should do both since they give different results. One measures the pressure that is created while the engine is cranked (compression stroke). The second test measures how well a cylinder holds pressure (leak down test). Since an engine piston utilizes a set of rings on each cylinder for sealing purposes (with different functions), both tests give a better picture of the ring and cylinder wall conditions.

FYI, these tests require two seperate testing tools...

barnacle · #19 06-28-2003, 01:06 AM

Bombardier not sayig much about it. Everything we are being told is that the Bombardier family is going to purchase it. The family sits on the board so if they took control of the shares it would have been inside trading. This is the reason why it had to public and put up for sale. We have been told no matter what they will end up with it. As for a leak down test you can buy the tester at a auto store and you need a air compressor. Bring the piston up till the intake and exhaust ports are closed then lock the flywheel up and fill the cylinder with air and it should not drop more then 10% as it sits a few mins. A 235 can show compression anywhere from 95 to 130. As long as there is not a 15lb. difference down the bank.