1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

[spencroy]

Hello Everyone,
I hate to ask a symtom based question, but I need to know where to start my investigation.

History:
This engine has been running great for many months now

What happend.
Yesterday while out fishing I was coming back across the lake at WOT and after a sort of "pop" the engine stalled. The boat came to a rest and I got that sinking 'this is going to cost alot to fix' feeling and decided to see if she would start back up.

She did, and would idle ok, but something is just off now, it doesnt sound exactly right. I put her up on plane and then gave her a little more juice and it sounded almost above the engine noise like a metal on metal tapping.

Assuming this was not good, I killed it and trolled her in.

My question(s):
Based on this symtom does it sound like I blew a gasket or busted a piston or something else?

Is a compression test my best first step in trying to debug what exactly is wrong?

Thanks for any advice and suggestions to get me started on where to drill in the fourms? I realize this is very vague, and if there is any other information I can provide I would be happy to. Just trying to get started debugging on the right foot.
Roy

 

[Fl_Richard]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

The free things should come first.

Visually inspect the engine for any damage.

Pull the spark plugs and inspect. - Do they all look the same? If not remember where the odd one was installed. Look for little metal shavings or clumps. Are they wet or dry, black or white, oily or clean as a whistle.

Check and write down the compression numbers for each cylinder.

Then check back here with the results. Your on the right board!

My WAG (wild mule guess) is that you have a scored cylinder and the extra resistance is causing the bearing or pin to knock. Don't run it unless absolutely necessary. The repair at this point points to a rebuild of at least that cylinder.... but lets not get ahead of ourselves

 

[kenmyfam]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

I may sound boring but a basic health check of your motor should begin any diagnosis.
Compression
Spark
Fuel delivery
Plug condition
Symptoms

 

[spencroy]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

Thanks for the starting pointers, and I think the news is probably pretty bad.

I removed the spark plugs last night. They looked pretty uniform, fairly black, but not to much build up to speak of. No noticable metal shavings etc, and only one plug may have been slighly wetter than the others (left middle).

I stopped by autozone tonight and borrowed the compression tester. I got appx 90 PSI on all cylinders except one...

The bottom right hand cylinder produces no measurable PSI. I thought this may be due to bad connections on the tester, but I am under the impression that I had a good airtight seal and the either:
1. this is correct behavior (pump or something)
or more likelyu
2. I am hosed, and at a min that cylinder will have to be rebuilt.

Whats the verdict?
Thanks guys
Roy

 

[Joe Reeves]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

Remove the cylinder head now that you have the psi readings so that you can inspect the head gasket cylinder and head sealing surfaces, cylinder walls and piston(s). Let us know what you find.

 

[spencroy]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

Remove the cylinder head now that you have the psi readings so that you can inspect the head gasket cylinder and head sealing surfaces, cylinder walls and piston(s). Let us know what you find.

Darn Joe, I was really hopeful that you might say anything but that. I have not removed the head before so I will be studying up in the service manual tonight (although this subject does not appear to be exactly covered).

It appears that there are 20 or so bolts holding that head in place. Any gotcha's or techniques I need to be aware of when I remove the head?

Will update with my results when I have them. Thanks for the advice so far.
Roy

 

[jogle1023]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

You dont have to remove the water jacket cover just remove the head bolt ( they are the ones on the very outside of the head).

 

[spencroy]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

Hey Guys,
A quick follow up on the head question. I removed the 20 bolts last night which according to the Service Manual are all that need to be removed before removing the head (although to your point jogle, I thought I was going to have to remove the water jacket just to get at that bottom left bolt on the head). The manual also points out that you may need to bang on the head with a rubber mallet to remove the head once the bolts are removed.

However, because this is the first head I have taken apart, I just wanted to check in with you guys to make sure those are the ONLY bolts that I need to be concerned with before hitting it with a mallet.

(There is a brass headed bolt to the right of the temp sensor which I dont know what exactly that is, so I have not removed it) better to ask the pro's before I go banging on the head

The other question/observation is the bolts on the block were numbered 1 - 20 on the head itself. I assume the reason for this is this is the order in which the bolts should be removed/installed? Is that correct or is there some other reason for this numbering scheme?

also... do I have any hope that there is a repair in this area that:
1. will cost < 500
2. will be fixable without removing the upper?
just looking for a ray of hope.... right now I keep telling myself I somehow blew a seal or something on that cylinder even though I know I am going to find that piston snaped in half or worse.

thanks
Roy

 

[Joe Reeves]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

The 20 bolts being removed..... the head should be ready to be popped off. Have someone holding onto it as you do not want it dropping to the floor.

The later style head gaskets has a sealing compound built onto them that sort of glue the head to the crankcase somewhat. A block of wood against the side top of the head and a good hammer will break that seal.

The "brass" bolt? No idea what that could be but it's very unlikely that it retains the head to the crankcase.

The hope thing? Remove the cylinder head first.

 

[jonesg]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

That might be a brass plug, in case you want a water temp sensor.

 

[CatTwentyTwo]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

The brass bolt is just a pipe plug closing off the water pressure port. It does not need to be removed.

 

[spencroy]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

So I pulled the head off and the conclusion I have draw is not to good.
---------------------------------------------------------------------
short version:
The symptom - "rough" edges of the piston in the cylinder with no compression, surface of cylinder inner wall not totally smooth (although close)

My fear - cylinder has to be bored, and the piston replaced
---------------------------------------------------------------------
long version:
With Joe's advice on not letting the head cover fall to the floor, and perhaps because it had just hung there all night, with a good tap the head came lose and I began to diag.

examined the suspect cylinder for metal shavings, but at first glance appeared to look good. I focused seal around the cylinder (praying) for any obvious sign of a breach, but it seemed to be ok.

I examined the head hoping to find a pin hole or something, but it appeared to be sound (sorry for the horrible img quality, click for larger pic).


I then put her in gear, and spun the prop forward to examine the piston cycles. I checked when the piston was all the way down for evidence of any metal or junk, but that seemed to check out ok.

Since this was my first time in, I figured my best troubleshooting approach was to compare the 2 cylinders with the good compression to the bad one. I gave each piston a good shove (per the youtube video in the compression thread how to's marinedoc) the first and second pistons were fairly firm, and expected the bad one to be loose, but it felt exactly the same as the other two.

At this point I was a bit perplexed and took a detailed look comparing each piston/cylinder. This is when I noticed that on 1 and 2 when fully extended out the edges of the piston were very smooth. The 3rd piston however, appeared to have small little chips( or scoring.. not sure how to descripe it, but very small) in them. The image does not show them hardly at all.

I used the prop to move the piston down and examined the cylinder wall, and when compared to 1 and 2 had to admit to myself that it did not feel as smooth.
----------------------------------------------------------------------
As such the conclusion I have draw is .. Joe or one of you will dash my last little bit of hope of a cheap repair bill shortly...might as well stop delaying

Whats the verdict?

 

[HybridMX6]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

I am sure others with more exp. will get in on this, but from what I see, are you sure that the head gasket wasn't blown? That lower cylinder on the head looks extremely clean compared to the one above it, almost as if it was pressure washed, which is what will happen if the head gasket blows. Of course, you could have cleaned it up before taking the pic, but I'm not assuming that.
Based on the pics, I don't see anything that would lead me to believe that cylinder would show 0 psi. Even if the small nicks in the piston are from it eating the rings (which there should be more evidence of them if that was the case, I would think it would still show a brief bit of compression, definitely not just 0.
Do you have any pics of the head gasket, or did it get mauled in the removal process from the glue?

 

[jonesg]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

I am sure others with more exp. will get in on this, but from what I see, are you sure that the head gasket wasn't blown? That lower cylinder on the head looks extremely clean compared to the one above it, almost as if it was pressure washed, which is what will happen if the head gasket blows. Of course, you could have cleaned it up before taking the pic, but I'm not assuming that.
Based on the pics, I don't see anything that would lead me to believe that cylinder would show 0 psi. Even if the small nicks in the piston are from it eating the rings (which there should be more evidence of them if that was the case, I would think it would still show a brief bit of compression, definitely not just 0.
Do you have any pics of the head gasket, or did it get mauled in the removal process from the glue?

agree, cyl head looks steam cleaned.
pity you didn't take a photo of the gasket , it would have shown telltale signs.
Does it sit flat on a sheet of glass or is there any wobble to it ( the head).

 

[spencroy]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

Thanks so much for the reply Hybrid, you are pulling me out of a deep spiral of depression if you are right!!!

I hate to do this, but due to an extreeme lack of inexperience and not being a mechanical person, I need some help understanding basic engine concepts around compression.

Silly question 1 - is what I think is a head gasket a head gasket?
(again sorry for the horrible image quality)

Ok, so my first question is when we are talking about the head gasket, is this the circular rubber o-ring around the top of they cylinder, or am I way off?

Silly question 2 - where does the compression actually take place?
My basic understanding of compression is as the piston rises to the top of the cylinder, the air/gas traped between the piston head and the head is compressed (to 90psi in my case). In order for the air to compress there has to be a seal somwhere between these two surfaces. The part I do not understand is where that seal takes place.


In the picture above, is the seal at point 1 (blue ring) or at point 2 (yellow ring).
If its the blue ring then the piston edges are not relevant and the only conclusion I can draw is that either the head is cracked, the gasket is leaking, or that I made a major error in my compression test. Which is very good news for me

However, if the seal is at the yellow ring, then in my mind the compression would being lost around the piston edges. However, when I look at the good cylinders I am not convinced that the yellow ring makes any sense as the compression seal point.

To your and jones point on the cleanness of the piston. That is pretty much how I found it. I did shoot it with a small burst of B12 and ran a rag along cylinder wall, but didnt touch the piston much.

My hope at this point is I made a serious mistake in my compression test, or that the problem is not as horrible as I feared.

I am out this weekend, but as soon as I understand what you and jones are referring to as the head gasket I will get some better photos.
Thanks so much guys.
Roy

 

[Joe Reeves]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

Picture taking hint for close up pics....... Have a good light beaming down on the subject, then cancel out the flash on the digital camera. I've found this scenario to ideally shown detail of the subject clearly..... eliminates the flashback problem.

I can't see the piston or the underside of the cylinder head clearly. However, if there are steel metal particles of any size imbedded in the piston top or the underside of the cylinder head, that spells trouble with a capital "T".

Looking forward to more pictures, including the head gasket. You mention cylinder 1,2, etc..... which actual cylinders are these you speak of. The cylinder numbering is as follows.

Port - Starboard
2...........1

4...........3

6...........5

Edit of 08/07/09 12:27 PM

Just saw the O Ring type seal gasket. My mind and apparently that of someone else was in the area of the older type head gaskets that would cover the entire surface of the head/block. If no apparent damage exists to the piston or cylinder head, and also if no cylinder scoring exists, that would lead me into a area of a faulty sealing O ring. Possibly w/o the flash, you can obtain a picture of the cylinder wall with the piston lowered?

 

[another todd]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

Is it possible you broke a reed valve????

 

[another todd]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

BTW the yellow ring is where the sealing begins. The head gasket is about a 1/16 inch thich gasket (similar to cardboard) usually with metal rings which which correspond to your yellow ring on picture, and is sandwiched between the head and block.. The gasket covers the entire surface except for holes which line up with water jacket holes and of course the cylinder. It may be stuck to the block.

 

[HybridMX6]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

Ok, Answer #1:
After looking up your specific model, it does appear your engine uses O-rings instead of head gaskets, so what you are pointing out in the pic is in fact the cylinder head o-ring. Rather interesting, I have a '93 60hp 3cyl and it uses a gasket.

Answer #2:
The compression happens simply between the top of the piston and the head. The seal that you are speaking of is what the cylinder head o-ring is for.

I would try doing as Joe Reeves suggested and take some better pics of both the head and the block in the areas of the suspected cylinder. If you are using a digital camera with a "Macro" feature, try turning it on and using that. It's for close up pics and works well. It usually has a symbol of a little flower or a rose.

In that o-ring, is there any sign of damage, rotting, broken, etc? If not, check the flatness of the head, it may have warped. Set it on a piece of glass face down and see if it wobbles, or use some sand paper on the glass and do a figure 8 motion very lightly, then look at the head. Should show ya if you have any high or low spots.

 

[HybridMX6]

Re: 1993 Johnson 150 - Did I blow a cylinder or worse? (based on these symptoms)

Image of your crankcase here from shop.evinrude.com

#36 would be the cylinder head o-ring