Compression on 1992 150 evinrude

[rocks]

Just put in a offer for a new boat with 1992 150 rude,and am getting a compression check done monday.What would a good reading be??

 

[Joe Reeves]

Re: Compression on 1992 150 evinrude

In the past, the compression on the V6 engines was approximately 125 psi, however at some point in the 1980s, the compression was dropped to approximately 95 psi to compensate for the poor quality gasoline we were faced with.<br /><br />To answer your question, the normal reading of the engine would be in the area of 90/95 psi.

 

[R.Johnson]

Re: Compression on 1992 150 evinrude

A compression guage can read all over the map.Most guage's have a 1/4" pipe thread, they can range from $5.00 to what ever you want to spend for a calibrated guage. Plus they have a check valve, with a , " who know's what quality". I don't think I have ever seen two in agreement. The best guage would be a leak-down tester, but the best is pull the cylinder head off an look. It seem's every one is reluctant to do this, but it has saved me a lot of time, and grief. I own both of the above guage's, I have been fooled by both.

 

[rocks]

Re: Compression on 1992 150 evinrude

Had compression done 1-3-5 = 80psi and 2-4-6=85psi ? What do Ya'll think.

 

[Joe Reeves]

Re: Compression on 1992 150 evinrude

Like R.J. states, the readings will vary from gauge to gauge. I'd say that the readings you received are pretty close to normal. For some reason, one bank will read slightly lower than the other bank, which you have discovered.<br /><br />I questioned a factory rep about the difference in readings between banks some time ago. His reply was that it had something to do with the crankshaft design. Frankly, I don't know if that's the case or not but it appears to be a normal thing.<br /><br />Possibly a different gauge would read on one bank 90 psi, and on the other bank 95 psi. We'll see what R.J. has to say about it.

 

[rocks]

Re: Compression on 1992 150 evinrude

My worry is 80 psi is too low.I undrstand diffrences in guages,but what if his is on the high side?

 

[rcrdei]

Re: Compression on 1992 150 evinrude

rocks<br />I have a v20 I bought last year with a 1989 evinrude 200xp.When I bought the boat it read 85 on all cylinders with my guage and 80 with the owners guage.A friend of mine is an OMC mechanic and he said for that year that was an ok reading.The main thing he said was that all cylinders were within 5psi of each other.I run my boat all the time and it does fine.

 

[R.Johnson]

Re: Compression on 1992 150 evinrude

As I recall at one of the service school's they stated that the bottom, or cylinder's 5, and 6 on the V6 engine's would run lower. I don't recall just how that was accompliced. The important thing is the difference in the reading's between cylinder's. As I have said, I have been fooled by these test's. More than once I have found that the cylinder reading the highest will be the one that is damaged, I have no explanation for this. My practice is to use the compression guage, and if there is much of a difference, follow up with a leak down test. With this test, you will not only see the difference in the guage reading, but hear the air leak, or rush through the engine. The only way I can think of to check a compression guage would be to have a calibrated guage to check it again'st.

 

[dafox99]

Re: Compression on 1992 150 evinrude

I guess they could have a shorter throw (shorter journals) on the cylinders where they want lower compression. A reading of 80 indicates a compression ratio of 6.5:1 where 95 is 7.5:1. <br /><br />In some very high output motors, I think some non-intuitive things are done that most humans don't contend with. Asymmetrical cranks and counter-balance shafts to eliminate resonance and crank twist (the top cylinders have to twist the whole crank to drive the load, where the bottom ones are connected more directly to the load). I have no idea if any of that is going on.<br /><br />When I worked at a shop, we charged a nominal fee to dyno a motor for customers. Wonder if shops do that any more? If you have only slight variance in compression between cylinders, and are supplying nearly rated hp, I'd think you are OK.

 

[phatmanmike]

Re: Compression on 1992 150 evinrude

my 1991 johnson 225 reads about 90psi across al six, give or take 3-4 psi<br /><br />i heard once that the compression ration was set at 6.5:1<br /><br />but what do i know<br /><br />i think youre right where you should be

 

[clanton]

Re: Compression on 1992 150 evinrude

The compression too low this engine.

 

[clanton]

Re: Compression on 1992 150 evinrude

The 60 degree V6 not same as 90 degree V6. The 60 degree engine were 115/120 psi. The 90 degree loopers 100psi when new. Some 60 degree engine had some difference in cylinders when new. If the cylinders are down to 80 psi, I would pull the heads for a look, or bore scope the cylinders.

 

[rocks]

Re: Compression on 1992 150 evinrude

Thank you guys. It didn't even come down to a compression issue,broker took me out for a sea trial and boat wouldn't even run.Seemed to be fuel related.So I passed ,I don't need another maintance head ache.