'81 Mariner 115 hp Inline 6, Compression on one cylinder low...

[honda460ex]

Any opinions on this? I know gauges can vary, but I only have one gauge and it reads 120psi on cylinders 1,3,4,5,6. However cylinder #2 is reading around or just shy of 100psi. The motor acted up a couple weeks ago on the lake while running on plane and dropped around 1,000rpms. When I did come off plane it didn't want to go back up on plane and acted very weak and sluggish. Mechanic looked at it and said the coil was very weak on cylinder 5. Replaced the coil, wires, and plugs. Idles a little better but still doesn't want to come up on plane. I don't have a spark tester like the mechanic did so I really can't check to see if the spark is any stronger compared to the other cylinders, but all cylinders do have spark. Trying to test it by myself and not get jolted when checking each cylinder ='s no fun. Did a test on the trigger and it seems to be in specs for all cylinders. I have myself so frustrated and confused from thinking on it so much I don't know which direction to go. I have thought vacuum leak, power pack, or low-compression. But is that compression low enough to hurt me when compared to the other five?

 

[jimmbo]

Re: '81 Mariner 115 hp Inline 6, Compression on one cylinder low...

if #2 is reading 20lbs lower than the rest there might be a problem. Did you recheck #2 to verify the results? It might just be a sticky pistin ring, or it could be a broken ring and/or scored cylinder wall. Now days there are little cameras you can stick in the sparkplug hole and take a look for scoring of the upper cylinder walls. You could try doing a decarb on the engine it, if the compression is low due to a sticky ring, doing so might loosen it up.

 

[Chris1956]

Re: '81 Mariner 115 hp Inline 6, Compression on one cylinder low...

I do not think the compression is an issue. It is within 15% on a 31 year old motor, which is in spec, as far as I am concerned. If you are curious, pull the top transfer cover and look at the cylinder walls and piston. Concentrate on fixing the other issues. Remmeber if could be carb as well as spark problems.