Evinrude 150 (low compression on 1 cylinder)

Dudemaaan · Feb 25, 2010

Hello new here to the forum, just been reading through the FAQ area, looks like there is a lot of information on this site. A buddy of mine gave me a boat an '86 skeeter with a 150 Evinrude V6 identification plate : E150STLCDC. One cylinder has low compression (55) all others are around 105 -110

I've never worked on marine engines but I'm very mechanically inclined and have experience with rotaries and all kinds of automotive piston engines, so I'm sure I can figure it out.

My buddy that had the boat before, said sometimes the boat would run great like nothing was wrong, and other times it didn't have enough power to get on plane.

He said he tried running sea foam through it, so I'm guessing there is ring damage. Been trying to research as much as I can so I can go about fixing the engine.

daselbee · Feb 25, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

Hello,
Probably scored a cylinder due to running lean...maybe caused by a dirty carb...etc.
Not enough to go on yet. But you have to pull the head of the affected cylinder and examine the cylinder walls. Damaged cyl walls, burnt piston, etc. all require engine disassembly and machine work.
You have got to do a complete analysis of what caused it in the first place, so it doesn't happen again to the newly repaired engine.

If you get into it, remember that I am parting out the same motor, and if you need used parts, I will make you a great deal on them.

Private message me if interested.

ezeke · Feb 25, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

Could be just a blown head gasket, but you won't know until you pull the cylinder head off for a look.

Dudemaaan · Feb 25, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

Alright i'll look into that. If it is a blown head gasket would you hear the compression escaping or anything like that? The head looks pretty easy to pull.
Just unbolt all this right? Was also told the cover in the second picture (bypass cover?) can be pulled to get a view of the pistons and such.

daselbee · Feb 25, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

What you are referring to are the "bypass covers". That is not what you show in pic2.
They are on the "other side" of the cylinders, the side of the cylinders closest to the edge of the cowling, and are small plates that can be removed to look into the intake side of the piston/cylinder. There are 6 of them.
Go to shop.evinrude.com, drill down to find your motor, and in the cylinder and crankcase section it is item #14.
Note the mechanical mess that is under the exhaust cover while you are there.
The big cover shown in pic2 is the exhaust cover, and is best not removed if nothing is wrong under there.
I truly hope it is a bad head gasket, because the fix is much simpler for that.

ezeke · Feb 25, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

Only remove the bypass cover for the one cylinder that has a low reading.

There is no need to unscrew the water cover on the cylinder head, just the 14 cylinder head bolts.

mikesea · Feb 25, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

pull the cyl head ,did the sparkplug have aluminum buildup,often a lean condition will leave residue on the plug,if it happens to be a bad cyl.you can rebuild the engine ,those 150 crossflow engines are great engines,yours looks like its clean,was it run mostly in freshwater?you say your mechanical,so YOU can rebuild it,if you have just one bad cyl.it is possible for $$$ reasons to just do the one cyl,but the whole powerhead must be totally torn down,bad cyl will likely need to be bored to an over size that takes any damage away,a piston set which includes rings and wrist pin ,will cost about $90.A gasket kit ,maybe $75,I suggest rebuilding carbs,you may have had a lean condition causing a melt down,BUT,you may be lucky and just need a new head gasket,anyway,congrats on the gift.let us know how u progress

Dudemaaan · Feb 25, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

Thank you all for your quick responses and knowledge on the subject. daselbee I might take you up on your offer depending on how things check out in my engine.

The sparkplug didn't have any signs of detonation that I could see, although I'll have to ask my friend if he tried changing them or anything. he was also the one that did the compression test 2 years ago so I suppose the plugs could be in different cylinders. I'll pull them all and have a look.

Should I pull the head or the bypass covers first? Thanks for clarifying the location, I have a seloc manual and it had one picture of the bypass cover but I couldn't tell what I was looking at. When I asked the question on another forum I was told the wrong location. (or misunderstood)

ondarvr · Feb 25, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

You can pull either one first, but you'll need to see if the head gasket is blown also, so it doesn't make much difference.

The head gasket will cost more, but if the side of the piston and rings looks bad then you'll be buying new ones anyhow, if they look good, then the head gasket will most likely be bad.

daselbee · Feb 25, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

Dudemaaan said:
Should I pull the head or the bypass covers first? Thanks for clarifying the location, I have a seloc manual and it had one picture of the bypass cover but I couldn't tell what I was looking at. When I asked the question on another forum I was told the wrong location. (or misunderstood)

I would just pull the head first. Leave the bypass cover intact, you won't have to re-gasket it if you don't mess with it. Notice that the head is literally covered with bolts....there are only 14 to remove to get the head off. They are the ones that are around the outside perimeter of the head. The others, on the raised up water cover, can stay.

If you have to machine the block, you will have the whole thing apart anyway, and then the bypass covers will have to be re-gasketed upon re-assembly.

Dudemaaan · Feb 25, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

I think I'll pull the cylinder head first. If I have ring damage It will all have to come apart anyways. But if it's just the head gasket I won't "need" to pull the bypass cover. I might be able to see something when I pull the head too, and it looks like an easy starting point.

Solittle · Feb 26, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

Save yourself a lot of headaches and get the OMC shop manual.

Dudemaaan · Feb 28, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

I have a seloc manual already, whats the difference between that and an OMC manual?

parrisw · Feb 28, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

If the compression test was done 2 years ago, I'd do it again, just so you know for yourself, were every cylinder is actually at, trusting numbers from 2 years ago isn't the best idea.

jonesg · Feb 28, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

www.outboardbooks.com

the omc factory is printed just for your engine, the whole book.
How many engines does that seloc cover and what range of years?
I wouldn't change a coil without the factory service book.

kenmyfam · Feb 28, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

Dudemaaan said:
whats the difference between that and an OMC manual?

Quite a lot. The OEM manual is the best tool you can buy.

jwbmarine · Feb 28, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

kenmyfam said:
Quite a lot. The OEM manual is the best tool you can buy.

-----absolutely,...the best tool,..in the repair arsenal..!!!..the seloc,and clymers,..are for building fires...

Dudemaaan · Feb 28, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

Well I did some work on the boat today. Mostly just studied parts and read the manual. Put a battery in, fixed the starter then I took another compression test (Cold), all numbers were lower, maybe due to the engine being cold or the cylinders being dry from sitting. The low cylinder read 45 this time, and the others were around 85. After the first compression test I put a little oil in the low compression cylinder retested, and it came up to 80, i then removed the tester, & cranked the engine over to clear the oil next reading was at 60.

One thing I found very odd is the 2 lowest spark plugs are clean as can be. They look brand new like they have never been fired. The other 4 are very black.

Also from the very beginning of testing today I found no spark at any of the plugs. I've done my research and next time out will follow a series of tests to figure out why it's not firing. I'm hoping it's just the key switch grounding out.

Didn't pull the head, plan to sort out the ignition system then see about getting it started and maybe take it out to see how it does on water. Thinking maybe the engine wasn't firing on all plugs which is why he was having issues getting on plane. Will update as I progress.

ondarvr · Feb 28, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

Clean plugs typically mean water is getting in.

Dudemaaan · Feb 28, 2010

Re: Evinrude 150 (low compression on 1 cylinder)

One of the clean plugs is on the chamber with still normal compression. They are super clean like brand new in appearance. I asked my friend and he said he replaced all 6 at once. It's very apparent the others were run on. I guess the water would put the flame out and prevent combustion hense why they would look super clean. The alternative is an ignition problem just on the 2 lower cylinders which seems unlikely. If it was the head gasket wouldn't I hear the compression escaping around the head and wouldn't that mean the other cylinder should have low compression too? And would the small amount of oil I put in the cylinder have any effect on compression if it is head gasket?

Evinrude 150 (low compression on 1 cylinder)

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