Johnson 112 spl no compression(pic added)

[QuietRider21]

Hey guys..well i just picked up a 96 wellcraft with a 112 johnson on saturday for what i thought was a good price.. owner claimed it ran good. he jumped the selenoid to show me it turned over and all that but it needed an ignition switch. took his word for it, got it home. put a new ignition in and very hard to start. it did start, but hard. go to check compression, 3 cyclinders good and one at 20 psi. SUCKS!!!!!!
i'm no mechicanic..what would be my next step? pull the head? is there any chance it could just be a head gasket?
i'd appreciate any help

 

[mars bar]

Re: Johnson 112 spl no compression

Re: Johnson 112 spl no compression

Squirt some heavy oil in the bad cylinder and do another compression test< if the pressure goes up then you have a bad rings.

 

[QuietRider21]

Re: Johnson 112 spl no compression

Re: Johnson 112 spl no compression

tried the oil and nothing. pulled the head and found a tiny crack on the piston..i dont see any pitting or scoring on cylinder walls. heres a pic...

 

[QuietRider21]

Re: Johnson 112 spl no compression

Re: Johnson 112 spl no compression

and another pic..since i have good compression on other cylinders, can i attempt replacing just the bad piston? can i remove this piston as-is or do i need to pull the whole powerhead? thanks!

 

[beagleboy]

Re: Johnson 112 spl no compression

Re: Johnson 112 spl no compression

From what I can see your piston has some serious damage at the 3 4 5 o'clock posistions. You may have either a seized or broken ring. Replace piston...

 

[Joe Reeves]

Re: Johnson 112 spl no compression

Re: Johnson 112 spl no compression

Unfortunately, regardless of whether all pistons were bad or you simply needed to replace a ring set, the powerhead needs to be removed, completely torn down, cleaned, and in your case bored oversized no doubt on that cylinder at least and a new oversize piston installed among other things.

And the guy that said this engine ran good..... well, he's a lying *** who purposely took you, that is unless you picked it up dirt cheap and you don't mind investing a few thousand more.

 

[QuietRider21]

Re: Johnson 112 spl no compression

Re: Johnson 112 spl no compression

how can i get to the piston to pull it? do i need to remove the whole powerhead?

 

[Joe Reeves]

Re: Johnson 112 spl no compression

Re: Johnson 112 spl no compression

I believe I answered that question.

 

[QuietRider21]

Re: Johnson 112 spl no compression

Re: Johnson 112 spl no compression

sorry i didnt see your post when i replied..thanks for the info

 

[QuietRider21]

Re: Johnson 112 spl no compression

Re: Johnson 112 spl no compression

btw, do you know what would cause damage like this to a piston? a leaned out motor? overheat?

 

[whalerfreak22]

Re: Johnson 112 spl no compression(pic added)

From what i can see in your pictures the motor has been running lean for sometime and has gotten to a point where it is starting to break apart...Hence the low compression.

 

[Joe Reeves]

Re: Johnson 112 spl no compression(pic added)

One fouled high speed jet would be enough to cause one cylinder to run lean. This eventually leads to pre-ignition, melted piston, etc. (Usual cause).

 

[QuietRider21]

Re: Johnson 112 spl no compression(pic added)

ok my next question. since i dont see it being worth it to spend 2500 to have it rebuilt.. Sucks that i have to resort to this but i'm out a good amount of money now because this jerkoff seller. should i part the motor out or sell it as a whole? i'm probably going to use ebay.

 

[Joe Reeves]

Re: Johnson 112 spl no compression(pic added)

Parting it out would bring in more money, just takes more time to get rid of it all. Have you thought about tearing it down to see just exactly what parts and machine work might be involved and do the job yourself? Free labor and usually about $500 in parts etc invvolved.

If you intend to sell the crankshaft, pistons, powerpack etc etc, you would need to tear it down anyway. Something to think about.

 

[Cricket Too]

Re: Johnson 112 spl no compression(pic added)

Yeah but's either spend $2,500 on a rebuild, which isn't a bad price, or buy something else used and not know it's condition or how much it's been beat on over the years.

I say rebuild what you have and start with a clean slate, especially if you want something reliable.

That's what I did with my 115, got a rebuild from Flagship and started fresh. Engine runs perfect.

 

[QuietRider21]

Re: Johnson 112 spl no compression(pic added)

yea, ive thought about tearing it down and rebuilding it myself but i have no experience at all working on motors. i would hate to buy the parts and and spend the time only to find out i did something wrong down the road or not have proper running motor.
Cricket: i completely agree with ya. i'd rather have piece of mind with a rebuilt motor..whats holding me back is the fact i have 19' 2400lb wellcraft and 112 johnson. on this size boat, a 112 seems adequate at best(possibly underpowered)..i think i'm better off finding a 150..what do you think?

 

[Cricket Too]

Re: Johnson 112 spl no compression(pic added)

I have almost the same engine (115) on a 19' Sea Pro walkaround cuddy, around 2200lbs. It pushes the boat great. It always jumped right up on plane and I could cruise at 25mph at 42-4400 RPM. Rips at 36-37mph at WOT of 5700RPM, not crazy fast but pretty damn good.

When I got the powerhead back from Flagship it's even better now, it moves the boat out great, and sips fuel as well, I can fish all day and only burn 12-15 gallons of fuel and I have a long run to the ocean inlet and back to fish, and that's including moving around from spot to spot all day. It's a great engine for that size boat.

I think a 150 on that boat, while no doubt fun, will just burn extra fuel, and I don't know if you'll ever be able to take the full advantage of it unless you were always ripping at WOT.

Plus you're never gonna know what a used 150 has been through. Even if the compression tests out good, how are you gonna know it's not carboned up and a ring is about to stick and break in 5 hours?