1990 115 vro johnson low compression!!

[BEKO1212]

i have a johnson 115 with low compression. any ideas of what it could be from?

 

[lmuss53]

Re: 1990 115 vro johnson low compression!!

How long has it been sitting? It could be stuck rings. Pull the plugs and soak it down real good with PB Blaster and recheck it in a day.

You really need to give some more info. What year and model, has it been running recently, if so what happened, if not read the top secret file on awakening a sleeping engine?

 

[emdsapmgr]

Re: 1990 115 vro johnson low compression!!

What compression numbers do you consider low?

 

[JB]

Re: 1990 115 vro johnson low compression!!

Howdy,

Welcome to iboats.

No numbers, no answer, BEKO.

What exact procedure did you use to get numbers? What exact numbers did you get?

http://forums.iboats.com/showthread.php?t=391323

 

[BEKO1212]

Re: 1990 115 vro johnson low compression!!

the motor is a 1990.i just bought the boat and the person i bought it from had it sitting for 5 years.
the compression #'s read 35,40,80,81.the guy told me that they had low compression when i was buying it.
he said it could be from ethanol in gas.

 

[wilde1j]

Re: 1990 115 vro johnson low compression!!

Why did you ever buy it??

 

[BEKO1212]

Re: 1990 115 vro johnson low compression!!

well i bought it because it was cheap.1990 sunbird $300.and i have a johnson 155 i was going to put on boat
but just in case i wanted to see if i can get the 115 running good before putting new motor in.

 

[archcycle]

Re: 1990 115 vro johnson low compression!!

80 and 81 are very low to begin with, but 35 and 40 wow.

Did you get those numbers yourself or are those the numbers the prev owner gave? If previous owner, I'd check myself.

If they are indeed that low then you will need to first pull off the cylinder heads and see what kind of damage there is because there is almost certainly damage. I say almost because you have a one in a million chance that the heads are just finger tightened on there!

Either way, pull them off and inspect. Low compression like that will require a rebuild. All 4 cylinders bored out and new pistons and maybe (depending on what you find once you pull them) even new heads.

Post pics of the insides of the cylinders (turn the flywheel clockwise to get the pistons to move out of the way) and the inside of the heads.

Oh, and what happens when you turn the key?

 

[emdsapmgr]

Re: 1990 115 vro johnson low compression!!

You don't indicate whether the low compression numbers are on the same head... If so, you may have a bad head gasket seal ring on the low compression side. Could be an easy fix.

 

[kenmyfam]

Re: 1990 115 vro johnson low compression!!

Agree with the others we need a whole lot more information before any real advice can be given. Testing method, try different compression tester, which cylinders etc etc.

 

[iwombat]

Re: 1990 115 vro johnson low compression!!

Just when you thought you'd heard everything that could be blamed on ethanol.

Low compression?

wow.

 

[wilde1j]

Re: 1990 115 vro johnson low compression!!

Maybe pattern baldness too ... ?

 

[iwombat]

Re: 1990 115 vro johnson low compression!!

Now THAT I've heard


(Sorry to hijack the thread - carry on)

 

[BEKO1212]

Re: 1990 115 vro johnson low compression!!

He said ethanol possibly damaged motor.workin all weekend will do new compression test done monday and post it.

 

[BEKO1212]

Re: 1990 115 vro johnson low compression!!

i guess u dont know ethanol can do damage to engines. read a little about it and u might learn something
today!!

Just when you thought you'd heard everything that could be blamed on ethanol.

Low compression?

wow.

 

[JB]

Re: 1990 115 vro johnson low compression!!

i guess u dont know ethanol can do damage to engines. read a little about it and u might learn something
today!!

That is hogwash and mythology, BEKO. Just because someone printed it doesn't make it true.

If ethanol could damage engines why do the Indycars run on nothing else??

 

[archcycle]

Re: 1990 115 vro johnson low compression!!

My Johnson factory manual says my 1990 motor is approved to run 87 octane (87 (R+M)/2 or 90 RON) with 10% ethanol . It follows with a statement about ethanol related maintenance. It may be a different HP but I feel comfortable assuming your 1990 115 is too.

Assuming for the sake of conversation that it is related to ethanol-- Sure it can cause damage but in a round-about way, not directly. Don't use a fuel/water separating filter or don't empty it regularly and change it seasonally, don't clean/inspect/change fuel lines, don't do any basic maintenance, and you'll eventually have a problem. DO the basic fuel system maintenance and you won't have an ethanol related problem. People who don't do it seem to find it easier to blame the ethanol than their lack of maintenance. Your motor's previous owner may very well have been one of those people.

Or maybe it had nothing to do with maintenance or ethanol

One thing you'll learn about fixing someone else's basketcase motor is that it doesn't matter what the PO said, true or not.Just start clean on it.