1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

[speed_demon]

I just tested the compression on a newly acquired 1998 Evinrude 115hp and I'm a little concerned. 80-83-82-84. I heard the loop charged motors test low but 80 still seems really low. Tested at WOT.

 

[trendsetter240]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

Those numbers are very low but they are consistent which makes me question your gauge. Can you try this gauge on another motor to see what it reads?

Compression on that motor, at sea level, should be 110-135 psi.

Is the battery fully charged?

Did you remove all spark plugs before running the tests?

 

[speed_demon]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

Those numbers are very low but they are consistent which makes me question your gauge. Can you try this gauge on another motor to see what it reads?

Compression on that motor, at sea level, should be 110-135 psi.

Is the battery fully charged?

Did you remove all spark plugs before running the tests?

Battery isn't great but I had a good charger on it and it was turning over quickly. Plugs removed. I'm not sure about the gauge. The last time I used it it seemed low too but not that low and it was a old tired engine. I guess I could hook it up to my compressor and see if the numbers match.

 

[floridaboater1]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

Is the outboard running? If yes how is it running? Did you run the compression test with the engine warm or cold? I would take a little oil and squirt it in the spark plug holes rerun the compression test. If your compression rises you need rings...

 

[speed_demon]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

Is the outboard running? If yes how is it running? Did you run the compression test with the engine warm or cold? I would take a little oil and squirt it in the spark plug holes rerun the compression test. If your compression rises you need rings...

This motor is on a boat I bought a couple months ago. I live in Alaska and it's a jet so rigging up cooling is a bit difficult right now so I have not had a chance to run the engine yet. Besides that it's been sitting for a couple years so it needs some attention first. I'd just feel a lot better if I knew the compression was good. I'm hoping it's my gauge. I'm afraid to run a wet test and realize my fears. Baby steps... I'll test the gauge first.

 

[boobie]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

If it's been sitting for a couple of years, a good decarb may help it.

 

[Lenard]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

Don't worry too much, compression is fine.

 

[JB]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

Don't worry too much, compression is fine.

Agree. When all cylinders read close, but low, I always suspect the gauge or the technique.

 

[speed_demon]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

Yeah the carbs definitely need to be cleaned. I pulled one of the carbs sets and the engine and carbs were flooded with premix oil. I've heard of wintering but this is ridiculous! He must have hooked up the oil/fuel lines wrong. No wonder he hasn't run it in a few years and sold it in the dead of winter. I hope tilting the engine will drain most of it. The good news is everything looks like new internally. When I get off work I'm going to try to rig something up to test the gauge.

 

[speed_demon]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

I borrowed another tester and got 105-99-106-104. I sprayed some silicone spray (all I had) in the low cylinder with no increase. Turns out the hose on my old tester is leaking. The old gauge was within 1psi but both gauges read low with the old hose. This test was done with intakes removed so I think this is the highest it's going to read cold.

 

[trendsetter240]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

I borrowed another tester and got 105-99-106-104. I sprayed some silicone spray (all I had) in the low cylinder with no increase. Turns out the hose on my old tester is leaking. The old gauge was within 1psi but both gauges read low with the old hose. This test was done with intakes removed so I think this is the highest it's going to read cold.

Those numbers are fine. I'll bet they come up after you have run the motor for a few hours. Give it a treatment with seafoam or another de-carb agent before you start using it in the spring.

 

[speed_demon]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

That makes me feel a lot better. I've been doing some research and I found a post on this forum by metriccrescentwrench that was quite enlightening.

"As far as "normal" compression numbers, it seems that around 80 to 90 is typical. A few weeks ago I finally found an explanation of why loopers show lower compression than other engines. They have an additional small idle relief port above the exhaust port which aids in starting and idle quality (by effectively altering port timing at lower rpms). As rpms increase, more and more of the exhaust gas exits through the exhaust port (because of it's small size the idle relief port can only flow a small amount of gas), so port timing in effect returns to normal."

From what I've read loopers have many advantages but idle quality is not one of them so it makes sense to me.

 

[trendsetter240]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

Yeah, that's correct about loopers they are not the best motors at idle. They like to be at WOT. Crossflows can idle very smooth but don't match the loopers for performance and fuel efficiency.

I'd disagree that 80-90 is "normal" compression for a looper. My loopers, I've owned a dozen or so, have always been 100-145 psi. Anyways, the most important result of a compression test is that the cylinders are within 10% of each other.

 

[dazk14]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

Yeah the carbs definitely need to be cleaned. I pulled one of the carbs sets and the engine and carbs were flooded with premix oil. I've heard of wintering but this is ridiculous! He must have hooked up the oil/fuel lines wrong. No wonder he hasn't run it in a few years and sold it in the dead of winter. I hope tilting the engine will drain most of it. The good news is everything looks like new internally. When I get off work I'm going to try to rig something up to test the gauge.

The bowls are likely full of oil from cranking the engine without fuel in the lines. They'll drain out fine.

 

[speed_demon]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

The bowls are likely full of oil from cranking the engine without fuel in the lines. They'll drain out fine.

I hope so. The last thing I want to do is put the carbs back on and have them gum up again.

 

[xbacksideslider]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

I checked compression on my 115 V4 today - 89, 90, 92, 90

 

[bob johnson]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

i have a 1995 Ocean runner V4 looper. and I checked the compression last week all 120-130 psi....

i have a 1988 johnson 48 special.. and the compression is 150 psi in both cylinders!!

I guess it depends on how they designed the motors...

but it just seems to me that a motor that is supposed to have 130 PSI, and is 115 hp......has only 90 psi.. then it cant be putting out the full 115 hp!!

ill also add. that I have a 97 90 hp looper and the 95 115 looper. I reworked the 90 HP into a 115..by adding the 115 carbs, and manifolds, and 115 hp head, as well as reporting the sleeves on the 90 to match the ports on the 115.
but the heads are about .090" deeper on the 90 hp than the 115..( the book says they are interchangable....but only because they ACTUALLY bolt up...not because they are THE SAME)

i think since the bore and stroke of the motors are identical...that the compression on the 90 would have to be lower than that of the 115....IE lower compression= lower HP.



bob

 

[xbacksideslider]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

But what about this post -

http://forums.iboats.com/johnson-ev...84psi-low-compression-591277.html#post4101930

regarding "idle relief port" above the exhaust port?

 

[bob johnson]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

But what about this post -

http://forums.iboats.com/johnson-ev...84psi-low-compression-591277.html#post4101930

regarding "idle relief port" above the exhaust port?

THAT "PORT" is about a 1/8th" dia hole aprox 3/8" above the exhaust port.

but if one guys V4 looper is 135 lbs.... then most should be similar.... I have heard many people haveing 120- 130 lbs

and i have that in both the motors i have together at the moment... even the one i rebuilt( but havent assembled yet) had 125 psi across the board.


I know 2 cycles are a wierd animal and not as cut and dry for compression as a four stroke


or it doesnt seem to be to me anyway

bob

 

[xbacksideslider]

Re: 1998 Evinrude 115hp Looper 80-83-82-84psi low compression???

Bob - You make sense. I wonder what the book says.