NO COMPRESSION ON LOWER CYLINDER

H

holla

Cadet
Joined
Jun 2, 2005
Messages
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HELLO,<br /><br />I HAVE A QUESTION REGARDING MY COMPRESSION TEST RESULTS. <br /><br />MY TOP CYLINDER HAD A RESULT OF ABOUT 145psi AND MY LOWER HAD "NO" RESULT :( .<br /><br />THE LOWER ONE WASNT EVEN READING 10 psi. I DID THE TEST TO EACH CYLINDER ABOUT THREE TIMES AND HAD THE SAME RESULTS.<br /><br />CAN ANYONE HELP ME WITH THE RESULTS? <br /><br />THANKS IN ADVANCE..........CHEERS
 
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Dhadley

Supreme Mariner
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Feb 4, 2001
Messages
16,978
Re: NO COMPRESSION ON LOWER CYLINDER

Welcome!!<br /><br />What motor is it? Really doesnt matter though at this point. The next step is to pop the head off and take a peek.
 
H

holla

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Messages
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Re: NO COMPRESSION ON LOWER CYLINDER

hello dhadley,<br /><br />its a 1995 johnson 50HP outboard. <br /><br />At first I thought it was my VRO pump because i was getting a warning horn. I had it disconnected and now I run a 50:1 mix.<br /><br />I took it out on the lake wed and i was able to idle and troll but as soon as i went to go full throttle i had no power or the engine would stall out. <br /><br />any suggestions would be great.<br /><br />once again thanks<br /><br />cheers
 
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Dhadley

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Re: NO COMPRESSION ON LOWER CYLINDER

I'd pull th head. We may be finding out what that horn was about.
 
H

holla

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Re: NO COMPRESSION ON LOWER CYLINDER

i just took it out for the first time since last summer about 2 weeks before.<br /><br />it ran fine. i was able to go about 30 mph no problem. that same weekend i took it fishing and thats when the problems started(sluggish and louder). but i was able to drive it.<br /><br />this wednesday is when the s*&% hit the fan
 
H

holla

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Re: NO COMPRESSION ON LOWER CYLINDER

just took apart the motor. the bottom piston has a hole in the center about the size of a dime. filings everywhere. rings are shot as well.<br /><br />i was told the hole was caused by my spark plugs being too long. im not convinced because they were the ones recommended in the manual and gapped to specs.<br /><br />i was also told it may be that the engine was burning the gas too hot. carb problem.<br /><br />what do you think? any suggestions.<br /><br />im going to bore and replace both pistons i think.<br /><br />take care
 
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Dhadley

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16,978
Re: NO COMPRESSION ON LOWER CYLINDER

What plugs were you using? We need to figure this out so we can correct the cause. We dont need a repete performance.<br /><br />Also a 1995 50 is a 3 cylinder motor. Lets get the model number before you order the wrong parts.
 
H

holla

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Jun 2, 2005
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Re: NO COMPRESSION ON LOWER CYLINDER

no its a 2 cylinder, i just took it apart.....<br /><br />2 pistons....(2 cylinder)- upper and lower<br /><br />the model number is VJ50BELESR<br />ser. no is G 02514190<br />the plugs i were using are "champion QL78YC"
 
H

holla

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Re: NO COMPRESSION ON LOWER CYLINDER

Can you tell me what each of the following means?<br /><br />model number is VJ50BELESR<br /><br />i was reading up and i think my motor is a 1990. i was told it was a 1995 when i bought it 3 years ago. if this is the case some parts i bought may not be for both years but only one and the other year a different style.
 
D

Dhadley

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16,978
Re: NO COMPRESSION ON LOWER CYLINDER

Yep, thats a 1990 (ES). Most parts for a 1995 are different. A few are the same, not many. What did you order?
 
H

holla

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Re: NO COMPRESSION ON LOWER CYLINDER

i ordered an impeller. i have already installed it.<br /><br />the parts looked the same so i didnt think anything of it. after i figured out last night my motor was a 1990 i got that sick feeling. <br /><br />i was trying to remember the parts i have put on my motor since i got it 3 years ago.<br /><br />thanks for your help. its greatly appreciated
 
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Dhadley

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16,978
Re: NO COMPRESSION ON LOWER CYLINDER

Yep, thats the same. I wouldnt worry too much about what youve put on in the past. If it were different, itd be way different.<br /><br />What bothers me is that is the correct plug although I dont care for it personally. We still need to figure out what burned the hole in the middle of the piston.
 
H

holla

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Jun 2, 2005
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Re: NO COMPRESSION ON LOWER CYLINDER

thats what i thought. i crossed reference my plugs and the same number came up.<br /><br />do you think running the motor too rich/hot (vro might have backed up) could have caused this?<br /><br />any suggestion on the carb having a problem?<br /><br />cheers
 
D

Dhadley

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Re: NO COMPRESSION ON LOWER CYLINDER

I dont believe a oil pump issue would burn a hole in the center of the piston but that warning horn meant something.
 
D

DJ

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Re: NO COMPRESSION ON LOWER CYLINDER

I agree with DH. Oil pumps do not discriminate between one cylinder over another. Carbs-do!
 
H

holla

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Jun 2, 2005
Messages
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Re: NO COMPRESSION ON LOWER CYLINDER

thanks all.........<br /><br />im boring the powerhead..........no oversize piston and installing a new carb kit. im changing the plugs as well.<br /><br />ill let you know in a week or two if all is well.<br /><br />thanks once again<br /><br />cheers
 
M

mikeyzx2

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May 1, 2005
Messages
633
Re: NO COMPRESSION ON LOWER CYLINDER

ya'll don't suppose the hole was caused by detonation do you? I've seen photos from hot rod magazines where these guys were running the nitrous and high compression and all that and oftentimes burning a hole in the center of piston, kinda like holla is describing.
 
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