What got in the cylinder

[snagalager]

My 1981 90hp evinrude evidently had something get in the cylinder and smashed it but nothing is in there now and I dont have compression on that cylinder now. And theres not a hole in the piston. The other three cylinders have only 30psi on them. Do these motors have valves? Does anyone have any ideas what could have got in there? And whats a good manual to do a rebuild?

 

[hidef]

Re: What got in the cylinder

You want to order the OMC/BRP Service Manual you can get it at

http://www.marineengine.com/parts/parts.php#manuals

 

[Sixmark]

Re: What got in the cylinder

Did you remove the head and verify any of this, or are you speculating?, if you actually looked inside .....were there deep scores on the cylinder, you could have very well broken a ring, or for that matter cracked a piston, it's not uncommon in motors that are run with a lean fuel mixture for too long.

 

[snagalager]

Re: What got in the cylinder

Yes I pulled the head and it and the piston have marks on them like a piece of metal got in there banged around and disintegrated. I say that cause there are no pieces of anything left inside the cylinder/head

 

[retiredfornow]

Re: What got in the cylinder

The pieces may be lying down in the crankcase. Broken rings or reed valves come loose? Cylinder will definitely be scored. What causes the low compression? Did this happen while you were running the motor? or did you just buy this motor? Need more data. Looks like a tear down to me. Good luck.

 

[snagalager]

Re: What got in the cylinder

Is this a good manual? Does this manual give enough info to do an overhaul? Manual# 392075

 

[boobie]

Re: What got in the cylinder

Mtr defineately needs a tear down but why 30psi on the other cyls? Bad compression gauge??

 

[levi_tsk]

Re: What got in the cylinder

yes but you can get the same one on ebay - i got the one for my '81 140 for 25 bux gently used

and i agree too time for a teardown

 

[snagalager]

Re: What got in the cylinder

Im wondering the same thing about the 30psi readings. May be it is a bad guage. I rented one from autozone that was brand spanking new that I unwrapped and it was bad so I took it back and now have the guage that gave me 30psi readings. Im going to charge my cranking battery and check compression again in the morning. I may even go and trade it in for another one again.

 

[levi_tsk]

Re: What got in the cylinder

go to harbor freight tools they have em for 15 bux i RARELY shop at autozone as almost everything they have is second rate garbage from china - at least harbor freight is first rate from china lol

 

[scanman]

Re: What got in the cylinder

Just wonderin guys. Could the loss of compression on the three "good" cyls be caused by a warped or cracked head? Could it have seperated the gasket? Think that was a piece of a broken ring?

 

[rtek816]

Re: What got in the cylinder

It was a broken piece of ring. I've had similar issues with a 140. Probably didn't break the gasket loose. The weak link is the aluminum piston and aluminum head. Look closely and you might see a piece of shiny steel imbedded in that head. Try a different gauge. Good luck on your rebuild.

 

[snagalager]

Re: What got in the cylinder

I know I had 90 psi or greater on other cylinders. What would cause that to drop from 90 to 30psi when that cylinder went out? Just bad rings all the sudden? Thats if its not another bad compression gauge.
Do you think I can get away with just replacing rings and gaskets? The cylinder walls are not too bad.

 

[levi_tsk]

Re: What got in the cylinder

do like rtek said that piece may have cracked the head and your pressure is leaking into the water jacket hopefully not but its QUITE possible

 

[snagalager]

Re: What got in the cylinder

I bought a new compression gauge and took Autozones back. Now I have 90+ psi on the other three cylinders zero on the other. Does anyone know what compression reading would be the lowest before doing a rebuild? And what would the readings be with new piston rings?

 

[Daviet]

Re: What got in the cylinder

The "0" reading is the lowest you can go before overhauling.

 

[snagalager]

Re: What got in the cylinder

Yes, obviously. Was just curious for future reference. Is 90psi about the lowest you wanna go?

 

[Monte1961]

Re: What got in the cylinder

Daviet. Is that is that + or - 0?

 

[boobie]

Re: What got in the cylinder

Now Monte, thats a good question and something to ponder on. I'll be up all night thinking about it.

 

[Daviet]

Re: What got in the cylinder

Someone on here needs a time out .