Checking the Compression

[FLbound]

Hello there,<br />Newbie with a question. I checked all of the other related post out there and got some really great information. I am trying to check the compression on my 1983 Rude 115hp and had a question. After you run the motor for a few minutes to warm it up, and then take out the spark plugs and ground them, then screw in the test kit. do you then make about 4-5 turns on the flywheel by starting it up manual or by key? just a little confuessed on that. also while I am doing the compression check how can i do a proper spark check? thank for any help.

 

[Joe Reeves]

Re: Checking the Compression

Check the compression by cranking the engine over via the electric starter.<br /><br />You can crank the engine by using a small jujmper wire from the battery terminal of the starter solenoid to the small 3/8" nut terminal that energizes the solenoid/starter (not the 3/8" ground nut).<br /><br />The spark, at cranking speed, should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP!<br /><br />Spark Tester - Home Made<br />(J. Reeves)<br /> <br />A spark tester can be made with a piece of 1x4 or 1x6, drive a couple nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere.<br /><br />Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:<br /><br /><br />..........X1..........X2<br /><br />.................X..(grd)<br /><br />..........X3..........X4

 

[11craigt]

Re: Checking the Compression

Joe Reeves, awesome. But I think I'm lost with how these nails go together. Can't you just dangle the plug by the cylinder and have sombody crank it. If you get spark your happy...you just don't know how strong it is...is that the idea of the 7/16" gap jump? Is there a bad as in damaging way to check spark? I got the same 1983' 115 EVINRUDE. Remember Joe?

 

[mikeyzx2]

Re: Checking the Compression

anchor, have your buddy or "favorite" brother in law hold the plug close to block and crank it.....that's a damaging way to check for spark. be sure he's standing on WET ground also <br /><br />the spark tester Joe Reeves is describing is the safest, and easiest way to go. a good, hot spark will jump that gap and be blue, whereas a weaker spark will be more yellow, if it even jumps the gap. there's a post showing a picture of a homemade spark tester, do a search for it...