1982 envinrude 140HP V4 problem

[jojo1975]

repaired

 

[Bosunsmate]

move the piston to top dead centre see if you can push the piston through sparkplug hole with something that wont damage the piston, i use a big screwdriver with a rag on the end.
when you push it you shouldnt be able to move the piston more than a couple of hair wdths, if it does move much more than that which would cause it to hit the plug then the bearings on piston or crankshaft a worn and will unfortunately need replacing before they go bang

 

[racerone]

Remove the bypass cover for this bad cylinder.---6 small screws and it allows you to inspect piston movement and piston rings.---This sounds like $$$$ repairs are needed.

 

[emdsapmgr]

These early 135/140 engines are not the same as their 90 and 115 brothers. The correct factory plug for that engine is the ul77-v or the qul77v. That's a tipless plug, just like the V6 crossflow engines of that vintage. Having said that, I'm somewhat surprised that the piston is hitting the plug tip. I've successfully run tipped plugs in engines like this when testing for lean conditions by checking plugs for color. Never a problem on a temporary basis. Any chance the head was milled by a prior owner? Is the top ring on that piston still intact?

 

[jojo1975]

repaired

 

[metriccrescentwrench]

Just to be safe check for piston play as suggested.

 

[emdsapmgr]

Has any internal work been done on the block internals since you had it? Any chance that the one piston is a non-factory replacement piston? 125 is good compression.

 

[jojo1975]

repaired

 

[racerone]

Plug gap closing up is a serious issue.----Pull the bypass cover on that cylinder.--Just 6 screws on that cover and a $1.00 gasket to replace.----Inspect for broken top piston ring.

 

[jojo1975]

repaired

 

[racerone]

This is a serious issue , but I think you are afraid of what you might find.-----Spend the $1.00 for the new gasket.-----Something is going on in there that is not normal !!

 

[jojo1975]

repaired

 

[jojo1975]

no more

 

[emdsapmgr]

Agree. If the top ring failed and was passed thru the powerhead while running, it's very likely that the affected cyl would have lower compression than the other 3. That's why I asked what had been done to the engine. Possible one/both heads were milled at some point in the past.

 

[jojo1975]

These early 135/140 engines are not the same as their 90 and 115 brothers. The correct factory plug for that engine is the ul77-v or the qul77v. That's a tipless plug, just like the V6 crossflow engines of that vintage. Having said that, I'm somewhat surprised that the piston is hitting the plug tip. I've successfully run tipped plugs in engines like this when testing for lean conditions by checking plugs for color. Never a problem on a temporary basis. Any chance the head was milled by a prior owner? Is the top ring on that piston still intact?

I got those UL77-V plugs works great the idle is even smother then before hold its idle better and for some reason it feels like it has more torque.