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140 OMC Compression Questions
sraab928	#1  Posted on 04/28/09 - 11:19 AM
Member Project Albums Posts: 1282 Comments: 13 Joined: 12/27/05	ok - my new to my 25 Outrage has a pair of 140 HP V4 OMC motors (I was told they were 150's)- They were VRO models (now disconnected). I have no idea on year or model as I cannot find the tag on either motor - they have been repainted a few times so who knows anymore. The boat is a 1982 if that helps. Anyway I just charged the batteries up and performed a compression test and got the following numbers on a cold engine. Port Motor Top L 135 - R 130 Bottom L 150 - R 135 Starboard Motor Top L 128 - R 125 Bottom L 135 - R 125 The 150 number scares me a bit as its a bit far off the other numbers. Supposedly one of the motors was rebuilt - Have receipts for .020 over pistons etc. But they also charged for new VRO pumps ($625) and these are clearly orginals and disconnected. Total work was about $7000 in the motors but its hard to tell anything other than new plug wires & plugs had been done. What do you guys think of these numbers? Scott 1974 21' Revenge w Mercury 200 ProXS V8
Derwd24	#2  Posted on 04/28/09 - 12:17 PM
Member Posts: 1607 Comments: 9 Joined: 05/09/07	Hi Scott, You're pretty close to the 10% variance between cylinders (those numbers sound more like crossflow design than looper). Are you able to look into the cyl's through the spark plug hole to see what the carbon situation is like in there? Am thinking the engines may benefit from a de-carb procedure, then you can run the compression test again? Dave - 1983 Outrage 22
sraab928	#3  Posted on 04/28/09 - 2:01 PM
Member Project Albums Posts: 1282 Comments: 13 Joined: 12/27/05	How do you tell if its a crossflow or looper? I remember loopers are generally lower compression... right? I have not done anything other than test and look them over - I will try an dpeak in and see what the cylinder looks like Scott 1974 21' Revenge w Mercury 200 ProXS V8
Derwd24	#4  Posted on 04/28/09 - 3:40 PM
Member Posts: 1607 Comments: 9 Joined: 05/09/07	Yes, loopers are generally lower. If you can see into the cyl, the top of the piston will tell you. Flat as a pancake is a looper. A piston head with a slope in it is a cross flow as the incoming charge hits the slope and is directed up into the cyl (as opposed to across and out the exhaust port!). Dave - 1983 Outrage 22
sraab928	#5  Posted on 04/28/09 - 5:24 PM
Member Project Albums Posts: 1282 Comments: 13 Joined: 12/27/05	I will check it out tomorrow - Thanks Dave! Scott 1974 21' Revenge w Mercury 200 ProXS V8
Whaler27	#6  Posted on 04/28/09 - 5:47 PM
Member Personal Page Posts: 32 Comments: 1 Joined: 10/11/06	The compression on my 1985 140 looper looked alot like your starboard motor -- all cylinders between 125 and 135.