No compression on two cylinders

[iloveketchup]

the motor (1990 140 Johnson V4 Looper) overheated and hit it's thermal cut off sensor limit. I tested compression and cylinder compression was about 100, 90 (port) and 90 65 (starboard). The starboard side overheated. Being new to outboards, i thought it was a stuck closed thermostat. i changed that out and the motor ran decent for a while. Then... it overheated again.

I tested compression and it was 0, 0 on the starboard sides.

So... when i take this apart, what am i going to find? Rings, pitted pistons, blown head gasket, combination of things? Is it likely going to be worth repairing?

The whole boat (Wellcraft V20 and motor) only cost me 800 so i'm not furious. I'm considering to use this motor and take a stab at fixing whatever it is.

 

[noelm]

Re: No compression on two cylinders

we can only guess, but you maybe lucky and the second over heat has blown the head gasket, but I think once you remove the head, you may find something very sinister. Remove the heads and check, only way to know, then fix your over heat problem, or be prepared to repeat the repair process.

 

[iloveketchup]

Re: No compression on two cylinders

well, i take back the second overheat. I was taking it for the first trip after overheat/thermostat repair. I had to make it about 2 miles to the ramp and pull it from the water for the year. The boat was a bit sluggish but did run decent WOT.

I had never been to this marina so when i got about 150 yards out, i throttled down and it cut out. Then it didn't want to restart. It was def on the way to overheat however, just cut out at low RPM.

I called up my buddy and asked, "where are you?". I heard him yell, "I'm over here!"

fortunately the marina sent out a couple of kids on a small 9.9 to drag me out.

it'll still crank/turn over and i don't hear anything clanging around. I did recall the motor would sneeze/miss a bit at very low RPM's.

 

[jonesg]

Re: No compression on two cylinders

Sounds like a blown gasket, check the cyl head for warping, that can be fixed ez enough.

 

[iloveketchup]

Re: No compression on two cylinders

well doc... how bad is it?!?!

What happened here? This is a little more than just a head gasket.

the lower starboard cylinder wall isn't looking so great. The top starboard doesn't seem that bad.

 

[noelm]

Re: No compression on two cylinders

new or second hand head coming up for you, could be much worse, cylinder damage does not look to flash, but I guess you could replace the head and gasket and see how it runs and for how long! make sure you repair the over heating.

 

[Sixmark]

Re: No compression on two cylinders

I took the liberty of doing a quick photoshop job of the picture of your head

The red arrows indicate blockages in the water passages, and the green indicate the fissure that was created when the gasket failed under compression.

This could have resulted in two ways, the blockages were present first which led to the hotspot in between the cylinders, causing the gasket to fail.

or

The gasket failed and all of the crap that was blowing through there accumulated in the passage way.

I would suggest that you pull the other head and check it as well, if the passageways look the same.

Is this motor run in saltwater by chance?

 

[nymack66]

Re: No compression on two cylinders

Hello my fellow V20 owner, sorry to see what happened to your power head.
Who ever told you its a 1990 140 v4 is wrong , Its more like a 86-87 ..Just a FYI when you order parts ...This a small bore looper ....
I have a spare head if you are interested let me know I send you pictures of it..You may want to consider to have the power head replaced with a rebuilt unit ..Call my buddy Vaun at http://www.powerheadexchange.com He.../amackhrandilal/New Engine/DSCF0002.jpg[/IMG]

 

[iloveketchup]

Re: No compression on two cylinders

new or second hand head coming up for you, could be much worse, cylinder damage does not look to flash, but I guess you could replace the head and gasket and see how it runs and for how long! make sure you repair the over heating.

I bought the motor and whole boat and $800. This is my first boat and outboard. It ran okay earlier in the season and then this happened. I named it "come on ilene". Ilene almost lasted all boating season. We got dragged into dock labor day.

 

[iloveketchup]

Re: No compression on two cylinders

I took the liberty of doing a quick photoshop job of the picture of your head

The red arrows indicate blockages in the water passages, and the green indicate the fissure that was created when the gasket failed under compression.

This could have resulted in two ways, the blockages were present first which led to the hotspot in between the cylinders, causing the gasket to fail.

or

The gasket failed and all of the crap that was blowing through there accumulated in the passage way.

I would suggest that you pull the other head and check it as well, if the passageways look the same.

Is this motor run in saltwater by chance?

Thanks for the edit. I'm still learning about these motors. I'll pull the other head tomorrow. The lower port has a really bad helicoil job in it that never allowed me to check compression. It's kind of sad this happened. Before the 2nd overheat i had at least 60 psi in the bad cylinder and maybe up to 90 on the top. :shrug: oh well. I live along a major road. I could get rid of this boat within a couple weeks and go find another haha.

Yes it was ran in salt water in Jersey. Waretown/Barnegat Inlet area to be exact.

 

[iloveketchup]

Re: No compression on two cylinders

Hello my fellow V20 owner, sorry to see what happened to your power head.
Who ever told you its a 1990 140 v4 is wrong , Its more like a 86-87 ..Just a FYI when you order parts ...This a small bore looper ....
I have a spare head if you are interested let me know I send you pictures of it..You may want to consider to have the power head replaced with a rebuilt unit ..Call my buddy Vaun at http://www.powerheadexchange.com He...'t so bad when you've got friends or sea tow.

 

[Sixmark]

Re: No compression on two cylinders

Just for your own future reference, if you get that much of a variance in compression between cylinders, do not continue to run the motor.

In many cases in a situation like that , you can just change out a head gasket before it leads to the problem that you had. It's one of those live and learn things.

But as they say, now you know.

 

[dazk14]

Re: No compression on two cylinders

Hello my fellow V20 owner, sorry to see what happened to your power head.
Who ever told you its a 1990 140 v4 is wrong , Its more like a 86-87 ..Just a FYI when you order parts ...This a small bore looper ....
I have a spare head if you are interested let me know I send you pictures of it..You may want to consider to have the power head replaced with a rebuilt unit ..Call my buddy Vaun at http://www.powerheadexchange.com He... about sending him some work. Thanks, Mike D

 

[nymack66]

Re: No compression on two cylinders

With a good core it was $1,400...

 

[jonesg]

Re: No compression on two cylinders

DIY for under $400 , including a cyl head.
Includes machine shop boring cyl oversize, new piston and ring set.