johnson 140hp compression

[tblshur]

i have a j140tlcte 1983 shop rebuilt about 1.5 yrs . i was told it was bored maybe 1 cyl dont know, did get 4 new pistons have run good on top end i did a comp. check 2 wks ago ,cold 3 cyl 95psi 1 98. should i do anything or be concerned about low comp.pressure gage was rental from auto parts,plugs were removed and grounded.thanks for any advice or suggestions.

 

[boobie]

Re: johnson 140hp compression

You compression sounds okay. Just remember, compression gauges vary. If it's running okay, run it.

 

[racerone]

Re: johnson 140hp compression

Perhaps the rebuilder installed the low compression head gaskets.---These gaskets were thicker than the originals.

 

[Faztbullet]

Re: johnson 140hp compression

Just add a bottle of Merc Quickleen or BRP Carbon guard to fuel regularly and run as always....

 

[tblshur]

Re: johnson 140hp compression

thanks guys for your quick replys. forgot to mention i remembered that it has never been re torqued, the heads that is . will that be ok maybe. thanks again for all the help you all do .:joyous:

 

[racerone]

Re: johnson 140hp compression

The torque on the head bolts should be checked after initial star-up and cooldown.---Not a bad idea to retorque once a year.----Loose head bolts are a major cause of leaking / blown head gaskets.

 

[emdsapmgr]

Re: johnson 140hp compression

That 140 engine normally had special factory high compression heads: 326502/503. Used on the 81-84 140 crossflow, and then on the bubble back 115 for a year. Normally, those should give compression readings in the 125-130+ range. Any chance the heads are a different part number? Those numbers are more typical of the later low compression bathtub heads. The fact that the compression is so even is good. Have you tried another compression guage?

 

[tblshur]

Re: johnson 140hp compression

thank you racerone good to know you can retorque after a year i will do. emdsapmgr now that you mention it ,when they rebuild, my heads had some pitts from broken rings he had some used heads he put on.if i put on right heads and bring the comp up to 125-130 range would that increase performance a lot .this is a great forum,thanks for all your help.:thumb:

 

[emdsapmgr]

Re: johnson 140hp compression

The 140 heads were always a sought after commodity, due to their inherent high compression capabilities. You will improve your performance by finding an original set. Not unusual for a rebuilder to change pitted heads, as the pits can lead to other bad issues, so I understand why. There is another residual issue: carb jetting. If the heads were changed out, but the carbs were not rejetted, (still jetted at 140 specs), likely the carbs are overfueling the engine somewhat. It won't cause a major problem, but wastes fuel and may degrade actual performance somewhat. With an engine like that, I'd be looking for an original set of heads.

 

[V153]

Re: johnson 140hp compression

Ya I'd try to find a set of the origional hi-comp heads too. It'll put a lot more spring in your step.

edit. Hi-comp on the right.

 

[V153]

Re: johnson 140hp compression

Fyi. Evinrude used hi-comp heads on some earlier motors as well. I have a '78 140 with hi-comp #322864(5) heads.

 

[V153]

Re: johnson 140hp compression

Fwiw if you have a head that's been dinged up by a broken ring, etc. It's not that big a deal. Knock off the rough edges & polish it up. "Craters okay, mountains bad."

 

[tblshur]

Re: johnson 140hp compression

emd that may be why my plugs always look really wet and foul out if i troll very much. seafoam has helped that.V153 the pics really help now i know what im looking for nice to know 78s will work also, ill be looking for used most likely.thank all you guys very much BIG HELP!!!:thumb:

 

[daselbee]

Re: johnson 140hp compression

Well....not all "high compression" heads are alike either. You must pay special attention to the mounting bosses for the spark coils. Some "humped heads" have the bosses, others don't. Also, the number you may find embossed on the head is a casting number, not the Evinrude part number that you might order at the parts counter.....head is likely NLA anyway, thought I would just mention it.

 

[V153]

Re: johnson 140hp compression

'78s have the coil mounts. Prior to that I dunno. Do know the '75 does NOT have them.

 

[emdsapmgr]

Re: johnson 140hp compression

The coil brackets were cast onto the heads starting in the 78 model year. Early 135 and 77 140 heads will certainly work, but you'll have to fabricate coil supports in order to attach them to the block. The 135 heads were actually higher compression than the 140 heads, so if you switch to them, you may need to flow just a bit more fuel through the carbs to keep the combustion chambers cool at WOT.