'92 135HP Mercury - no compression in one cylinder

TimS

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Jul 16, 2003
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Cruising along the beach at 3800 enjoying the ride, engine stops dead. Not really a concern, it seems to happen about once every 10 trips. Restart without issue, cruising a little slower around 3500 just to make sure everything is cool - and it stops dead. A little concerned. No noise, no sputter, it just cut out like someone turned the key. So I give everything a quick peek, pumped up the ball a little and restarted - now the engine is suddenly sluggish, bogging down - I don't push it but immediately stop and remove the cover - after a little searching, I see that the oil feed line before the T where it meets the fuel line is split, oil everywhere. So I think that must be it and replace the insanely weak clear plastic hose with a piece of thicker, black hose. Engine performs no better. Could find no other visible problems so I limp back to the marina.<br /><br />Following morning I have the marina do a compression check - I'm told you always start with a compression check, then go forward if that's good. Here's the kick in the arse:<br /><br />#1 - 130<br />#2 - 0<br />#3 - 125<br />#4 - 130<br />#5 - 125<br />#6 - 130<br /><br />How bizarre is that? If the split oil line - which was still likely flowing some oil, just not holding much pressure - was the cause of the #2 cylinders demise, why would the other 5 cylinders have such excellent compression? Is there a chance something else caused the #2 cylinder to drop to zero compression?<br /><br />The motor never made a noise, not a sqeak, not a squeal, it just went from running 100% to a sluggish, unresponsive hunk. <br /><br />I know a little about 2 cycle engines, but this is potentially going to be a serious financial investment to repair. Can any of you please give me some idea as to the following:<br /><br />1 - What potentially caused the failure of just #2 cylinder?<br /><br />2 - Could it have been the split oil feed line?<br /><br />3 - What would be the wisest plan of attack from here? Would it be possible to just repair this one dead cylinder since the other 5 are apparently in excellent shape based on their compression? <br /><br />Thanks in advance for your anticipated expertise, this is a real problem...primarily because it's a friend's boat - he understands that if the split line caused it, there wasn't anything I could have done to prevent it, but I still feel responsible even though it's only the second time I used the boat without him. Thanks again!<br /><br />TimS
 

KennyKenCan

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Aug 26, 2002
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Re: '92 135HP Mercury - no compression in one cylinder

Hi TimS,<br /><br />Unfortunatly the reduced oil delivery is probably the cause of the failure in #2 cylinder.<br /><br />The most likely reason for just one cylinder failing was due to weak rings in that cylinder.<br /><br />The worst part of it all is that the motor will most likely need to be rebuilt, which means that all cylinders should get new rings installed while the engine is apart.<br /><br />Hopefully, there was minimal damage to that cylinder and it will at worst need only to be rebored and new piston and rings installed.<br /><br />Regular inspections of the engine may have avoided this problem.<br /><br />Hope this helps.<br /><br />Kenny
 

TimS

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Re: '92 135HP Mercury - no compression in one cylinder

Kenny, thank you very much for taking the time to respond, I appreciate it.<br /><br />If I may impose, a couple more questions. You suggest that it "may" have to be rebuilt - is that a slip or is there perhaps another option that I should consider?<br /><br />One thing I should mention is that my buddy pulled each plug while we were on the water that afternoon that this happened to look for any damage or metal shavings on the plugs - each plug was pristine - does that give any more clues as to the likely condition of the bad cylinder or the possible solutions?<br /><br />Last thing - extremely rough estimate - any idea what it should cost to take it down, replace the rings and, if that's all that's necessary, rebore the #2 cylinder? I'm not gonna hold you to it, just curious how much this is gonna hurt ;) <br /><br />Thanks again, I very much appreciate your help.<br /><br />TimS
 

stocky

Seaman Apprentice
Joined
Apr 24, 2002
Messages
43
Re: '92 135HP Mercury - no compression in one cylinder

G,day<br /><br />I have a Mariner V6 150hp and the same thing has happened to me. My engine runs premix but I also broke a ring in number two cylinder. Now obviously the damage sustained was not due to lack of oil but I suspect was due to overheating.<br /><br />I am in the process of rebuilding and I am told that cylinders one and two on these motors are the most vulnerable due to lack of water pressure.
 

jdkzrt

Petty Officer 3rd Class
Joined
May 26, 2003
Messages
83
Re: '92 135HP Mercury - no compression in one cylinder

1)It doesn't sound like you burnt a hole in the #2 piston, but you need to confirm this. If you did, the repair might be much easier than you expect (remove carbs, intake and head and change piston only (as long as cylinder walls are good).<br />2) If you broke a ring and scored the cyl. wall (which is pretty likely), you will need to do a complete dissassembly and get a sleeve installed. (lots of labour).<br />Post what you find (especially the condition of cyl. wall).
 

NICK JONES

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Joined
Aug 9, 2002
Messages
29
Re: '92 135HP Mercury - no compression in one cylinder

That plastic oil feed pipe may just have split because the valve beneath it (part of the brass T piece) didn't open at 2 psi. These have been known to hold shut to around 10 psi. This in combination with an old,weak hose could have caused the split. Your engine might have been completely starved of oil becasue even a small split in the pipe would have prevented the oil pump pressure rising to 2 psi.<br /><br />Make sure when this motor is repaired that the valve is checked / replaced. It's good to have a clear pipe so you can see the oil !
 

KennyKenCan

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2,501
Re: '92 135HP Mercury - no compression in one cylinder

TimS,<br /><br />The posts by stocky, JDK, and WOODMAN just answered your question.<br /><br />Thanks guy's.<br /><br />Kenny
 

KennyKenCan

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2,501
Re: '92 135HP Mercury - no compression in one cylinder

TimS,<br /><br />One more thing...<br /><br />The reason the # 2 cylinder may have failed is because the temperature in the engine seems to run hotter at the top where the #1 and #2 cylinders are, cuasing the rings in those cylinders to become more brittle over time.<br /><br />These motors are notorious for running HOT!<br /><br />I have a '94 135HP and it normally runs between 160 degrees and 180 degrees, which I consider warm for an outboard.<br /><br />Kenny
 

TimS

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Re: '92 135HP Mercury - no compression in one cylinder

Thanks for all your help guys, I sincerely appreciate it. I run a site with 28 forums myself and can recognize a wonderful community when I see one
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I will certainly let the members of my site know about this forum anytime outboard issues come up.<br /><br />Back to the motor - I'm going to contact the mechanic at the marina and discuss with him the numerous ideas and possibilities you've shared with me. I spoke with the owner of the boat about it and he tells me it's an 11 year old motor and sometimes that's all the lifespan they are good for. So we'll explore some options and I will keep you informed as to what we find and what we end up doing. That will be my little contribution back to this wonderful resource :) If you ever need help surf fishing, lemme know, I know a thing or ten about that ;) <br /><br />Last question - lets say, on the outside chance, that the rings on the piston in the #2 cylinder magically aligned their openings, what sort of compression would that produce? Now lets say, instead, one of the two rings was stuck - what sort of compression would the remaining ring and the oil ring produce...if any? I only ask because there was no damage or metal shavings on any spark plug. Thanks again.<br /><br />TimS
 

KennyKenCan

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Aug 26, 2002
Messages
2,501
Re: '92 135HP Mercury - no compression in one cylinder

Hi TimS,<br /><br />You are now grasping for a miricle that's not going to happen.<br /><br />There is more than likely, damage done internally in your motor, which it's severity cannot be determined until either a partial teardown, or a complete teardown has been done.<br /><br />Sorry, no quick fix. :( <br /><br />Look at it this way, when your done rebuilding that engine, you will have essentially, a new motor, one that you will be able to depend upon, and one that could last you forever (with the proper care).<br /><br />Proper maintainence it paramont to a reliable outboard motor.<br /><br />Nothing can replace that!<br /><br />The reason that you don't see any metal shavings or anything like that is because the debris was most likely expelled out the exhaust when it happened.<br /><br />2 cycle motors are not like 4 cycle motors, there are no valves that the debris would have to pass, the exhaust is essentially just an open port to the atmosphere and the debris just gets pushed out and is on the bottom of the lake or ocean you boat on.<br /><br />If you are not mechanically inclined, then I would let a mechanic do the work.<br /><br />It will save you alot of agravation down the road.<br /><br />Hope this helps.<br /><br />Kenny
 

TimS

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Jul 16, 2003
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Re: '92 135HP Mercury - no compression in one cylinder

I wasn't really grasping at straws, just exploring (very) unlikely avenues ;) <br /><br />It's not my boat or motor, it's a good friend of mine's. He's generally extremely meticulous about maintaining everything he owns, but apparently, this one thing he missed :) <br /><br />Just for future reference, what specific maintenence may have prevented this from happening? What should folks normally do say once per season that would or could have prevented this? Fixin' it is something that's gonna have to happen...but I think understanding the proper preventative maintenence that may have avoided this tragedy would be very helpful :) Thanks again.<br /><br />TimS
 

KennyKenCan

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Aug 26, 2002
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2,501
Re: '92 135HP Mercury - no compression in one cylinder

TimS,<br /><br />Whenever I take the cover off of my motor, I look at everything and touch everything.<br /><br />I squeeze all hoses, cooling, fuel and oil, to check for them drying out and cracking.<br /><br />I check electrical connectors, to make sure they are fully seated.<br /><br />I look at the grounds for corrosion or looseness (Looseness...if thats a word) and anything that looks out of the norm.<br /><br />Outboards do require that they be looked after as they tend to vibrate alot, so you have to keep after them all the time.<br /><br />Hope that answers your question.<br /><br />Kenny
 

TimS

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Re: '92 135HP Mercury - no compression in one cylinder

Thanks again for all your help :) Unfortunately...or fortunately, depends on how yah look at it, it looks like we'll be repowering with a 2002 leftover - so we'll never know exactly what happened to the internals of this motor. Sorry, I was really looking forward to letting you know, for future reference, what the problem was.<br /><br />Thanks again.<br /><br />TimS
 

KennyKenCan

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Re: '92 135HP Mercury - no compression in one cylinder

Hey TimS,<br /><br />What are you going to do with the old motor?<br /><br />If you are just going to dispose of it, let me know.<br /><br />I'm always lookin for spare parts, and you can't be too far away from me.<br /><br />Kenny
 

foxjohnc03

Petty Officer 3rd Class
Joined
Jun 30, 2003
Messages
79
Re: '92 135HP Mercury - no compression in one cylinder

If your friend wants to sell the motor, let me know. I am looking for a project motor for my Glastron V-178. 135hp is right up my alley. If interested please email me at foxjohnc@comcast.net
 
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