1988 Evinrude V4 120hp Wet Test Compression Results Good or Bad?

[jmw129]

I need some feedback. I did a wet / compression test on my Evinrude V4 120hp and the results were 122, 120, 123, 132.

Are these results good for an engine of this age?

What range is considered good to excellent compression?

Low compression?

Any info you have on this topic is greatly appreciated!

 

[levi_tsk]

Re: 1988 Evinrude V4 120hp Wet Test Compression Results Good or Bad?

what do you mean "WET"? as in you put oil in the cylinders before testing? that invalidates the test... run the engine until its warmed up and repeat the test this time without putting oil into the cylinders the only effective means to raise the compression are :

1 decarb (using seafoam or a similar product as a fuel additive on top of tcw-3 oil)

2 rehone rering (complete tear down involved)

3 overbore (complete tear down involved)

anything over 100 and even is pretty good for any motor but the test MUST be preformed "dry" as in nothing in the cylinders that isnt normally there

 

[jmw129]

Re: 1988 Evinrude V4 120hp Wet Test Compression Results Good or Bad?

Yes there was oil in the cylinder. I have heard people say that the "Wet" test is the best way to test compression. I did the test with the engine cold with no oil.

The results for the cold (dry) compression test was 110, 103, 105, 80.

The cylinder that tested at 80 went up to 120 when I did the wet compression test.

I'm concerned that I may have a weak cylinder.

 

[backyard mechanic]

Re: 1988 Evinrude V4 120hp Wet Test Compression Results Good or Bad?

JMW... you did a complete compression test and it showed you what compression tests are intended to show. Wet and dry compression tests determine cylinder condition and ring seal.

It is possible there is a carbon build up or varnished up rings (a possible cause for the pressure differences between wet and dry). Try using a good quality 2 stroke oil. Synthetic is better because of better cleaning, less carbon and a cleaner burn. You can also try using a quality cleaner designed for cleaning varnish and carbon from ring lands. Keep an eye on your low cylinder. If it runs lean on fuel it may be the cylinder is worn and a rebuild is eminent. Top cylinders usually get hot and burn due to bad water pumps. Lower cylinders are burned by being lean. Check your link and sync to be sure you aren't over revved because your timing is too far advanced.

 

[levi_tsk]

Re: 1988 Evinrude V4 120hp Wet Test Compression Results Good or Bad?

you might...can you get it to run ??do this if you can...

first put a little splash of seafoam into the cylinders with the engine tilted up let it soak for one hour turn the engine over with the plugs out to blow out the excess seafoam and to prevent hydro lock
then
do a shock treatment decarb take a gallon of gas 3 oz of two stroke oil and 2/3rds of a can of sea foam and mix it all up in a seperate can run the engine on this mix and spraying the remainder of the seafoam dirrectly into the throat of the carbs while its running run it until the gallon of gas mix is gone ive heard this is best done while on the water but i cant see why you cant do it on the hose if you have to
if you do it on the hose keep the rpms low (below 2k) or you can get a runaway condition and trust me you dont want one of those

oh yeah and its gonna smoke so bad youll think your blowing it up, your neighbors will hate you for a week, and your mosquito problem (if you had one ) will be no more but keep it running thats the carbon burning off the rings and all the internal parts and dont be surprised if the prop starts oozing black goo from the exaust its normal thats how you know its getting clean ;D

retest the compression when your done and see if the numbers on that low cylinder comes up you numbers are borderline on that cylinder but it may come up after this procedure post back your results

 

[jmw129]

Re: 1988 Evinrude V4 120hp Wet Test Compression Results Good or Bad?

Hey Guys,

Thanks for the helpful information. Have Seafoam in the tank ready to hopefully clean out the weak cylinder.

When the start the engine, the engine wants & does seem to start-up fairly quickly. A few cranks and the old man is up & running (joke since it's an older engine).

Petty Officer you mentioned that the dry & wet tests provided the results as intended.

Given the compression of 80 dry (cold) not ran and 120 wet (oil in cylinder) should I be worried the cylinder is bad?

I read an article on outboard compression and the author stated that a "Good Working" outboard will have a compression reading of 65 to 75 psi and anything lower than 65 is a bad cylinder.

To me those number's seem scary to me. Seem's like most people are saying 105 to 150 depeding on age seem's to be the ideal compression number's.

Does the wet test better simulate the "Real World" performance?

**Backyard Mechanic I would like your opion on this reply as well**

I think alot of people are confused with compression number's since they seem to vary based on wet or dry compression testing.

Thanks!

 

[levi_tsk]

Re: 1988 Evinrude V4 120hp Wet Test Compression Results Good or Bad?

the thought is that if you do a wet compression and it comes up you may just have a stuck ring and thats why you got a low reading

- i disagree since a molecule of oil is probably 1000 times larger than a molecule of air i feel that the oil just plugs up the hole where the air is escaping and the only TRUE test of compression is dry after doing a decarb..... and since you didnt run it you didnt free up the ring if in fact it is stuck
JMHO and a i may not know what im talking about ... but thats my logic in a nut shell

dont borrow worry just do a decarb like i said above and retest if its still low post back