Compression test results- updated w/wet test

[bryandjohnson33]

I am a newbie to engine repair and would like to get some advice. <br /><br />I have a Mercruiser 488 (4cyl, 188HP, 3.7 L) engine. I have been getting a lot of blow by out the crankcase ventalition hose (going through a quart or more everytime I take it out). I did a compression test (dry) and had the following results:<br /><br />1- 90<br />2- 80<br />3- 160<br />4- 165<br /><br />What is most likey causing the low compression in 1 and 2? What are possible solutions? Is fixing this a do-it-yourself job? If not, how much is getting it fixed going to cost (approx)? <br /><br />Thanks for your help!

 

[sea wolf]

Re: Compression test results- updated w/wet test

check head gasket. while u have the head off take it to a machine shop & have it looked over for possible problems such as warpage. is engine running hot? it's not a big job to pull the head.

 

[Trent]

Re: Compression test results- updated w/wet test

Time to do a wet test also. Pour some oil down each sparkplug hole and re-test. If the readings come up its rings. If not its valves. Either way she going to have to come apart.<br /><br />Most likely you have a ring problem? Do the wet test to find out.

 

[bryandjohnson33]

Re: Compression test results- updated w/wet test

Ok, I did the wet compression test and got the following reults:<br /><br />1- 120<br />2- 90<br />3- 160<br />4- 162<br /><br />What does this indicate? And, how big of a loan am I going to need? <br /><br />Thanks.

 

[flashback]

Re: Compression test results- updated w/wet test

get a valve job done on the head and have it checked for warp, heck, just get it milled a little for fun.......

 

[Trent]

Re: Compression test results- updated w/wet test

Number 2 dont look so good. Before doing a full rebuild try this. Put some Marvel Mystery oil in the oil and the gas per directions and run for awhile. <br /><br />After running for awhile recheck the compression. <br /><br />But number 2 looks like a valve. Could be carbon build up??

 

[Boatist]

Re: Compression test results- updated w/wet test

First thing I would do is loosen lifter and make sure it is not just a bad lifter. Back it out 1 turn and check again. The valve lifter should be loose at this point as when adjusting go to zero clearance plus one turn. Make sure to do both valves for number two. When the compression comes up like on number one it is usually rings but number 2 could be bad valve, stuck lifter, valve adjustment, blown head gasket.

 

[bryandjohnson33]

Re: Compression test results- updated w/wet test

Thanks for all the suggestions. One last question (I hope)... What may have cused this problem in the first place? I am just worried that I will fix this only to find out later that there was something else causing the problem and I will have to do it all again. Any thoughts? Thanks!

 

[flashback]

Re: Compression test results- updated w/wet test

number 2 is flat, It may be sticking or have a build up on it. Hope Trent is right as that would be the best option for you...but do like he said and check it again after you add the marvel..the stuff works sometimes........