compression test slows down motor only on top two pistons

[mudrow]

Yeah Im new to outboards and they sure are strang beast. When I checked the compressoin the bottom 4 are about the same but the top two at (70#) are a little over half of what the other 4 are at(120#). also the starter motor turned the motor head over slower on both top two cyclinders on compression checks.I was thinking it has to do with the reeds and they may be stuck. Do you think that the decarb spray may loosen these up. Or does this sound right. inline 6 100 hp 63 model<br />thanks for any help (really)

 

[JB]

Re: compression test slows down motor only on top two pistons

Howdy, Mudrow.<br /><br />Reeds have no effect on compression. My guess is that a weakening battery had a lot to do with it.<br /><br />Recharge your battery and start at the top for next measurement.<br /><br />Good luck.

 

[LubeDude]

Re: compression test slows down motor only on top two pistons

All plugs out, throtle open some.

 

[mudrow]

Re: compression test slows down motor only on top two pistons

all plugs out trottle not open, checked twice when i done the first test. have gotten a seafoam product and sprayed in the top carb. I have rebuilt the carbs and will make another test tomorrow (friday) and see what happens.

 

[mudrow]

Re: compression test slows down motor only on top two pistons

compression shows the same thing. Plugs out trottle open. I took the small intake side cover off and it looks bad, real dirty and girmey and the pistons are dark. also the rings would not spring when I pushed on them. The 3 & 4 cyclinders look good, clean in cavity and pistons shiny. Havent looked at bottom two yet but will tonight when I get the head off the cowl. Looks like I have to try and rebuild this if the cyclinders are O K. Wish me luck.