What should the engine compression be?

[jack7771]

I have the Evinrude 1986 service manual, but I can't find anywhere in there what the compression is supposed to be. Does anyone have that info?​

1986 110 HP Evinrude
Model E110MLCDC
Serial # J1125677
Shaft length is 20"

Jack​

 

[david_r]

Re: What should the engine compression be?

i dont know about factory specs...............but as long as you are within 10% of each other then you are ok.

mine reads 125psi on all..........'79 johnson 115

it will still run good at around 80-85 psi........any lower and you will be using more gas than it is worth.


for example 110-65-95.............isnt acceptable

for example 100-90-95.........acceptable.

and i will tell you like many others on here 2 different gauges will give you 2 diff readings..........the important thing is equality.

a decarb will help improve comp a lot.................you can find it in the faqs

 

[tashasdaddy]

Re: What should the engine compression be?

well said above. there are not any published compression reading, due to the fact that guages read differently.

 

[jack7771]

Re: What should the engine compression be?

I had the compression checked at a Marine shop last year. Compression readings were 105/100 and other side 65/105. Can't remember what they were supposed to be. The shop said if the motor was doing okay don't worry about the 65.

I know the motor isn't performing at peak, but is generally doing ok. However, there is sometimes difficulty pulling a slalom skier up with a 15" prop. That prop, BTW, at WOT (5400 RPM) will push the boat (a 1986 16 ft. Starcraft -- dry wt. of boat only is 1000 lbs) at 36 mph with 4 people in the boat.

So, I am somewhat concerned over the compression and wondering if I should get the engine rebuilt.

Jack​

 

[david_r]

Re: What should the engine compression be?

i would do a decarb and recheck it.

it may be a stuck ring, broke ring, blown head gasket................worst case scenario is a galded (melted) piston. the longer this goes on the more damage you could do....................pull the plugs and get a good flashlight and see what the top of the pistons look like----or remove the head and really check it out-----gaskets are cheap compared to a complete overhaul.

http://forums.iboats.com/showthread.php?t=158076

that 65 the dealer said was ok is throwing the balance waaaay out...........its practically being drug along by the rest of the cyls.......further reducing your hp

 

[iwombat]

Re: What should the engine compression be?

Compression readings were 105/100 and other side 65/105. Can't remember what they were supposed to be. The shop said if the motor was doing okay don't worry about the 65.
​

Find a new shop.

That's a stuck ring, blown head gasket, or damaged cylinder/piston. None of which is good news, but can be fixed if addressed early.

Edit: Ok the damaged cylinder/piston can't really be fixed if addressed early.

 

[jonesg]

Re: What should the engine compression be?

"Edit: Ok the damaged cylinder/piston can't really be fixed if addressed early."

But address it before the rod goes thru the block.
Sounds like the mechanic wasn't on the ball at all.

 

[KLINDWW]

Re: What should the engine compression be?

There's a scoop, I shop that is turning down work. They must of already got their bailout check.

 

[iwombat]

Re: What should the engine compression be?

Turning down work, or waiting to sell a new motor?


hrm

 

[tashasdaddy]

Re: What should the engine compression be?

i would not return to that shop. sure sounds to me like a blown head gasket at the least. the other cylinders are with in reason. i do not think a decarb will bring the low cylinder back up that far. you can try it. but i think the head is coming off, to see what is actually wrong.

easy decarb
Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

afterwards compression.recheck

 

[jack7771]

Re: What should the engine compression be?

Well I decided to ask Doug his thoughts about it. He's an expert auto technician who's been out boating with me a number of times and was with me when I winterized the motor.​

He believes it's simply a worn or stuck ring, because of the way the motor runs and the way the spark plugs looked at the end of the season.

So, maybe my path of least resitance is to simply use a 13" prop for slalom skiing.

Jack​

 

[iwombat]

Re: What should the engine compression be?

Jack, I'll say this once and then move on.

You need to open it up and fix it, or you're going to be looking for a new outboard in short order.

 

[tashasdaddy]

Re: What should the engine compression be?

exactly what he said. ^^^^^^^. keep running it like it is, you may as well make an anchor out of it now. 45 minutes, and a $20 head gasket. may fix it. or then you can put the head gasket on it. then run it and ruin it. i would try the $20 option first.

 

[jack7771]

Re: What should the engine compression be?

Head gasket is not the problem.​

Jack​

 

[tashasdaddy]

Re: What should the engine compression be?

what did you find?

 

[nightstalker]

Re: What should the engine compression be?

If that mechanic told you that you could keep running her with a cylinders compression at 65, I'd lose that mechanic real fast!!!!!!!!!!!!!!!!!!!!
Nightstalker

 

[jack7771]

Re: What should the engine compression be?

what did you find?

Piston rings.​

Jack​