HELP WITH COMPRESSION TEST EVINRUDE 140hp

[mav6759]

I have a question about a compression test on a 1989 Evinrude V4 140hp....I checked the compression on this motor and i got good compression from 3 cylinders but the last cylinder didn't register on the gauge at all....Now I done a lot of compression tests and I never seen where a gauge didn't register something...I can see the piston moving and when i place my thumb over the spark plug hole i can feel some compression...So I double checked myself on that one cylinder and still the gauge would not register that one cylinder...My question would be, can I be getting a false reading or has anyone experienced a cylinder that had not compression at all.....

Thanks Mav.

 

[metriccrescentwrench]

Sounds like your only logical course of action is to pull the head to see what's going on.

 

[racerone]

It sounds bad.----Only one thing to do next and that is ---Remove the cylinder head !

 

[interalian]

Prolly a blown head gasket

 

[hemi rt]

Squirt some oil into the cylinder and take another reading - what did you get?

 

[boobie]

Pull the head.......

 

[mav6759]

No Title

I pulled the head this morning this is what i found..I found a hole in the head gasket, but the funny thing is, I got good compression from that bottom cylinder...Don't how with the size of the hole...My only concern now is a small chip on the block in the upper cylinder and that's the cylinder that had the low compression..The cylinders look very good...no damage as far as I can see..My question is can I repair this chip in the block or is the block done

 

[jakedaawg]

Post pic of entire gasket

Place head on flat piece of glass. Use feeler gauge to feel under it how warped is it?

 

[interalian]

That hole may just be a coolant passage. You'd be looking for a defect around the metal ring if you're losing compression that badly. And/or warpage per above.

 

[mav6759]

Thanks for the response, I see no damage to the heads, I did have the heads looked at a shop they found nothing...The only damage (or what I saw as damage) was on the block. Could that little chip make a difference in the motor not having compression. Also is there anything i can use to smooth that little chip out.

Thanks Mav

 

[racerone]

The heads are warped !--They all are.----Can be refinished on a glass plate and grinding compound.---Is the chip in the cylinder bore or on the gasket surface ??

 

[Chinewalker]

That chip defect is in the water jacket, not the cylinder area. Would not contribute in any way to your drop in compression. I'd be looking at the piston and cylinder walls on that cylinder for damage. The piston should move laterally in the bore a bit - with the piston at TDC can you see the top ring move when it does this? They should move freely in their grooves.

 

[mav6759]

Thanks for the reply we look at each piston and cylinder wall we could not find a scratch no where. Unfortunately we couldn't look at the Rings because we didn't want to take the pistins out.. The pistons were very clean. I can still read the numbers on the top of the each piston. But that head gasket was shot...I'm praying that this is a head gasket issue and not a ring issue....as I mentioned before, I took the heads to Napa machine shop and they say the heads were fine...the little chip is on the gasket surface...other then that the motor is very clean...I get the new head gaskets tomorrow morning....I will install and do another compression test and see if it stays on the back of the boat or go to the junk yard.

 

[racerone]

I say the heads are warped.--Put the heads together gasket suface to gasket surface.---Then hold them up to some light.-Can you see light between them ?

 

[oldboat1]

I wouldn't fret over it, or spend time trying to decide if the head covers are warped -- just resurface them in advance of installing new gaskets. I use 400/600 grit wet/dry sandpaper for ease of use. Use a figure eight motion on a flat, hard surface -- piece of glass is good. Your table top saw is also good, or a marble countertop. (Wet the underside of the paper so it stays in place.) Look for a uniform shine on the whole mating surface. Then follow the right torque sequence and specs for your motor.

Not sure if it's controversial, but think you can prep the block side of the mating surface too. Just carefully use a sanding block wrapped in wet/dry (not a sanding sponge -- not hard enough). Need to be tidy and clean up thoroughly afterwards (head cover too).

I think there is an outside chance the plug threads for the affected cylinder are slightly damaged or corroded (tester not quite sealing, possibly?). It still seems a little strange you can feel compression but not measure it. (Looks like it might be a salt water motor -- but in any case, gasket sure looks due for replacement.)

Don't think you mentioned running issues. Maybe poor idling. Stalling maybe. Curious about that.

 

[mav6759]

Thank for the reply, Napa look at the heads and he ran them through some machine and said the heads were fine and they look really good now...I was told if the heads were wrapped the machine would have found it...Never thought of the spark plug holes...I'll take a look at that in the morning..I just bought the motor, and iI have not had it running...The guy I bought it from told me that it had great compression when he stored it... So when i got the motor home, I did a compression test before doing anything...that when i found the bad cylinder...Also the motor was in salt water in Hampton, VA...3 questions

1. Does anyone have the right torque sequence and specs for this motor..1989 Evinride 140hp that would help me out alot...
2. Does anyone recommend putting anything on the head gasket before installing them.
3. if there was a little water in the cylinder, would that through off the compression test.


Thanks Mav

 

[oldboat1]

torque value should be 228 in. lbs, but can't help with sequence. See if your gaskets indicate anything about a sealant (some do). I normally do them dry. A blown gasket allowing water intrusion would affect compression test numbers.

You need a service manual if you are going to work on your engine -- parts manual at a minimum if you have some outboard experience. Here's an online source for service info: http://www.boatinfo.no/lib/evinrude/...rude.html#/380

Sounds like you distrust the seller. If so, will want to put in an impeller before operating.

Good luck with the project. (BTW, resurfacing is routinely done on the assumption that heads are warped to some degree -- just for future reference. Usually a simple exercise.)

 

[mav6759]

Thanks to all though's that replied...I changed out the head gaskets this morning...I got 120lbs on all cylinders except one, That one cylinder had no compression at all...here's the funny part...Before I change out the head gasket, I had no compression on the right lower cylinder, (that was the only cylinder that didn't have compression) after changing the head gasket, the lower cylinder went up to 120lbs...In the mean while, the top cylinder went down..Yesterday I had good compression from the top cylinder... now it won't register on gauge...(like the lower cylinder did before the head gasket change) it's like they traded places...I went over everything we did, re-torqued everything, took the heads back off the gasket was fine..[FONT=arial, sans-serif]. the heads are fine, it like the compression switch places...I never seen anything like it...Does anyone have any idea what could cause this...

Thanks Mav[/FONT]

 

[interalian]

Maybe there's nothing wrong with the motor and the tester isn't holding pressure reliably. Did you watch the tester whilst cranking?

 

[mav6759]

Thanks for the reply Yes...I checked the compression 3 times on each cylinder....and I can't figure out that is going on....I've never seen compression move from the upper cylinder to the lower cylinder...and back and forth.....It just doesn't make any since, i guess the next step would be to try to start it.... I was told to see if the starts, if it starts....let the motor warm up and then do another compression check....I will give that a try to morrow..

Thanks Mav