johnson 140 compression problems

[rlguns]

I have a 85 140 hp johnson (crossflow)it has about 20 hours on rebuilt.I could never get it pass 5200 rpms.Tried both a 21 and 19 pitch prop.no diffrence.About 42 mph is the fastes it would go.Well now the problem. The compression on 3 cylinders ar real closs to the same about 120-125 and the other is 90-95 psi.when i bought the motor i checked and they were 130-135 psi all of them.Broke it in exzctly like the mechanis said to. Like i said it was a fresh rebuid.What should i do?By the way its on a 89 model 17 foot stratos.

 

[dick]

Re: johnson 140 compression problems

If you can't see any damage through the plug hole you'll have to pull the head . Head gaskets are cheap and maybe you can catch the problem before it gets to bad.Just a guess but I"ve seen this engines break rings during or just after you break them in .Why ? don't know , nature of the beast I guess.You also said you had it rebuilt , have you talk to the shop about it yet ?

 

[its-a-sweater]

Re: johnson 140 compression problems

AGREE WITH ****. I WOULD PULL THE HEAD. BY ANY CHANCE IS THE LOW CYLINDER ON THE TOP? I BELIEVE THAT WOULD BE #3. IF IT WAS THAT ONE, ITS THE LAST TO GET WATER. MAKE SURE YOUR COOLING SYSTEM IS WORKING GOOD.<br /><br />YOU MAY GET LUCKY AND FIND THAT THE HEAD GASKET WAS BLOWING BY. IF THAT'S THE CASE, REPLACE THAE GASKET AND MAKE SURE YOU RETORQUE IT AFTER YOU HAVE RUN IT AWHILE.

 

[Dhadley]

Re: johnson 140 compression problems

What's the model number? A 1985 140 is a looper.<br /><br />Let us know exactly what you have and also WOT timing, spark plug type, type of fuel (and how old), type of oil (mixed or injected?) and water pressure readings.<br /><br />What happened to the motor that it needed to be rebuilt? Is this the same type failure? Same cylinder?<br /><br />Good luck!

 

[rlguns]

Re: johnson 140 compression problems

Okay , It has been a few months since i have checked anything so i went and done such , The power head is a 79 model i dont know why he kept saying it was an 85 . But anyway i am using ul77v plugs and i did recheck the compression and 1,3,4 have 105-110 and 2 had 90 psi.the engine is cold and has not been run in several months i dont know if that has anything to do with checking compression but the number 2 has had 90 since summer.Kinda wierd cause when i bought the motor it had 130-135.Also i did check with all plugs out im not for sure if thats the correct way or not.Please give advice.Also i tried getting up with the man who rebuilt it but no luck.that was when it was in warranty.looks like im sc******.

 

[its-a-sweater]

Re: johnson 140 compression problems

RL,<br /><br />LOOK CLOSELY AT THE PLUG THAT CAME OUT OF THE HOLE THAT HAD LOW COMP. IF IT WAS SUCKING WATER INTO THAT CYL. IT WILL LOOK CLEAN COMPARED TO THE OTHER THREE.

 

[rlguns]

Re: johnson 140 compression problems

it has no water coming thru ,i dont think the head gasket is bad. I just wasnt able to get the rpms up past 5200 and 40mph.Even with a 19 and 21 pitch.What was weird is between both props there were no diffrence.But back to the problem at hand the #2 cylinder has 90 psi could it have a broken ring? What could cause this?BTW it has no misses i mean it runs well just lack of full power but it acts like its just all its got.But it runs well.Thanks for all the help!

 

[its-a-sweater]

Re: johnson 140 compression problems

RL,<br /><br />THERES NO MISTAKING IT YOU'VE GOT A WEAK CYL. ITS JUST NOT PULLING ITS WEIGHT. I WAS HOPING IT WAS JUST A GASKET. I HAD A 115 LOSE A CYL. BECAUSE OF A GASKET. IT DID THE SAME THING. WOULDN'T REACH FULL RPM.<br /><br />A RING WILL DO IT. I JUST HOPE THATS NOT IT.

 

[rlguns]

Re: johnson 140 compression problems

what should i do re-ring that one cylinder or all .Will one of the rings be broke likley?I probably will do this myself i fell like i can.Whats the next step i guess is what im needing to know?

 

[G DANE]

Re: johnson 140 compression problems

Rl, you say the motor has been sitting for half a year. Did you mesure the compression before ?? If not, the ring in the bad cylinder might be loosened when the engine gets hot again. It is not fun changing rings on theese 115 th. hope you have some other error.

 

[G DANE]

Re: johnson 140 compression problems

RL sorry 140 not 115. You said you never got it above 5200, even right after break in ??

 

[rlguns]

Re: johnson 140 compression problems

Right after the last time i ran it the compression was on 1,3,4 around 120-125 and 2 was 90 psi .

 

[rlguns]

Re: johnson 140 compression problems

correct even when i first got it and compression was perfect it would not get above 5200 rpms and 42 mph.with a 19 and 21 pitch prop.There was not any diffrence between the 2 props.not any.The mechanic even help me set the hieght up on the motor so i think it is right .

 

[its-a-sweater]

Re: johnson 140 compression problems

RL,<br /><br />G DANES GOT A POINT. YOU MAY JUST HAVE A STUCK RING. MIGHT BE WORTH IT TO DE CARB IT FIRST.<br /><br />I WOULD TRY TO LOoK IN THAT SPARK PLUG HOLE. MAKE SURE NOTHING IS SCORING THE CYL. <br /><br />IF YOU'VE GOT IT APART. I WOULD THINK RE RING THE WHOLE THING. START OVER.

 

[rlguns]

Re: johnson 140 compression problems

So i could take the exaust cover off and look at the rings.Also what parts would be needed to re-ring the motor?

 

[rlguns]

Re: johnson 140 compression problems

okay i took the head off the port side and #2 cylinder the one that had 90 psi didnt look hardly as smooth as number 4 the top of the piston had alot of carbon build up and number 4 looked real clean.I dont know if it was just me but the piston seemed to have more play than # 4.the head gasket looked good and as far as i could tell without taking head completley off there were no cracks in it.Any Suggestions?

 

[clanton]

Re: johnson 140 compression problems

Ask the mechanic if he used wiseco pistons and if they were were clearance to orignal OMC specs.

 

[rlguns]

Re: johnson 140 compression problems

I do remember that it was not bored but dont know what manufacture.He said all the parts awere new.I wish i could find him i think he moved .

 

[johnkc]

Re: johnson 140 compression problems

riguns does the top of the piston look like it has been sandblasted ?if so you have had some degree of detonation.before taking the engine apart any further check your wide open throttle timing at cranking speed with the other two spark plugs out .be sure to ground all plug wires .curious to see if the timing was set too high ,wich could have detonated the piston .another thing that could have led to the piston det is a lean condition on that cyl...plugged jet in carb.

 

[rlguns]

Re: johnson 140 compression problems

The top of the piston is very brown looks like carbon buildup or such . I had a leak on the fuel pump and at the same time the mechanic took the carbs off and checked looking for that leak and they where all good (jets).It could be the timing , i will check.Say it is , what would that have done to make the compression low on that cylinder and what should be done to fix it?Adjusting the timing will not get the compression back up will it ?