User Tag List

Results 1 to 9 of 9
  1. #1
    Join Date
    May 2009
    Location
    Santa barbara, ca/boulder city, nv
    Posts
    1,002
    Thanks (Given)
    72
    Thanks (Received)
    9
    Likes (Given)
    42
    Likes (Received)
    17
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Typical for two top cylinders to have lower compression?

    Mine is a 1987 2.0L 150, but I bet this might just as well apply to all the classic V6’es...

    anyway, just did my five yearly compression check and everything was 120psi, except the top two, which were both 110psi.

    Is is that kind of typical for this family of motors?

    -Peter


    "padded wonder"
    __________
    the wet:
    Hydrostream Viper, 140 v4 crossflow, some Raker props
    16' Baja/Tahiti/Sidewinder clone, 135 v4 crossflow
    17' boston whaler alert, 90 merc fourstroke
    13' boston whaler, 40hp yamaha

    the dry:
    2003 bmw ///M5
    1993 mustang/griggs racing road race car
    and a handful of clunkers

  2. #2
    Join Date
    Feb 2014
    Location
    Missouri
    Posts
    982
    Thanks (Given)
    2
    Thanks (Received)
    46
    Likes (Given)
    10
    Likes (Received)
    59
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I’ve seen it on heavy boats and heavy pitch. Most see it on 5-6 from the last cylinder time issue.

  3. #3
    Join Date
    Feb 2009
    Location
    Dunnellon, Fl. / Cincinnati, Oh
    Posts
    386
    Thanks (Given)
    60
    Thanks (Received)
    26
    Likes (Given)
    125
    Likes (Received)
    146
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Cooling issue - Steam pockets?, or last 2 cyls. in line to receive cooling water, or both?
    Crud in the carb(s) leaning those 2 cyls. out?
    Got a 1988 2.4 175 HP. that compression tested @135 all holes except BOTTOM 2 @130.

  4. #4
    Join Date
    Feb 2009
    Location
    Dunnellon, Fl. / Cincinnati, Oh
    Posts
    386
    Thanks (Given)
    60
    Thanks (Received)
    26
    Likes (Given)
    125
    Likes (Received)
    146
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Motv18 View Post
    I’ve seen it on heavy boats and heavy pitch. Most see it on 5-6 from the last cylinder time issue.
    What's with the last cyl. time issue? Please elaborate!
    Would it then be good practice to "jet up " on these cyls. to avoid issues, or is there another remedy?

  5. #5
    Join Date
    Feb 2014
    Location
    Missouri
    Posts
    982
    Thanks (Given)
    2
    Thanks (Received)
    46
    Likes (Given)
    10
    Likes (Received)
    59
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    It tends to run about a degree or two more then #1, so if you’re doing performance setups you time off the most advanced hole which is normally #6.

    Its just rod length and wrist pin depths and crank twist all in spec but that all add up to a fast hole. Theirs quite a few write ups on timing I don’t have time to link currently. I think it’s also the lean side on some it’s the most common hole to fail.

  6. Thanks rochelle howell thanked for this post
  7. #6
    Join Date
    May 2009
    Location
    Santa barbara, ca/boulder city, nv
    Posts
    1,002
    Thanks (Given)
    72
    Thanks (Received)
    9
    Likes (Given)
    42
    Likes (Received)
    17
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    So my numbers yesterday morning were:
    110/110
    120/120
    120/120

    Went back and checked my numbers from five years ago and they were about the same. Somebody in a post back then advised that I use 89 and let her rip. I’ve been using 91 anyway. I get the feeling I could use 87, but not sure. It is a 1987 motor so that was well into the 87 octane era.

    -Peter


    "padded wonder"
    __________
    the wet:
    Hydrostream Viper, 140 v4 crossflow, some Raker props
    16' Baja/Tahiti/Sidewinder clone, 135 v4 crossflow
    17' boston whaler alert, 90 merc fourstroke
    13' boston whaler, 40hp yamaha

    the dry:
    2003 bmw ///M5
    1993 mustang/griggs racing road race car
    and a handful of clunkers

  8. #7
    Join Date
    Jul 2012
    Location
    Huntington, Texas
    Posts
    2,094
    Thanks (Given)
    211
    Thanks (Received)
    177
    Likes (Given)
    1352
    Likes (Received)
    857
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    76-78 2.0 1750's had tight heads and need good fuel. By '79 the chambers were opened up so lower octane isn't a problem. By '83 or '84 the floats were plastic instead of foam so ethanol gas is no problem...

  9. #8
    Join Date
    Feb 2014
    Location
    Missouri
    Posts
    982
    Thanks (Given)
    2
    Thanks (Received)
    46
    Likes (Given)
    10
    Likes (Received)
    59
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Merc put out a letter saying 87 was good when lead went bye. Unless specific noted in the ownership manual.

  10. #9
    Join Date
    Feb 2009
    Location
    Dunnellon, Fl. / Cincinnati, Oh
    Posts
    386
    Thanks (Given)
    60
    Thanks (Received)
    26
    Likes (Given)
    125
    Likes (Received)
    146
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Motv18 View Post
    It tends to run about a degree or two more then #1, so if you’re doing performance setups you time off the most advanced hole which is normally #6.

    Its just rod length and wrist pin depths and crank twist all in spec but that all add up to a fast hole. Theirs quite a few write ups on timing I don’t have time to link currently. I think it’s also the lean side on some it’s the most common hole to fail.
    Tolerance stack up, gotcha. Thanks!

Similar Threads

  1. What is typical compression for '98 225 3.0lt merc carb
    By CircleHook in forum Technical Discussion
    Replies: 3
    Last Post: 11-03-2015, 11:23 PM
  2. 97 mercury 2.5 200 xri low compression all cylinders
    By basscatjd in forum Technical Discussion
    Replies: 18
    Last Post: 09-05-2015, 07:28 PM
  3. Will I hate my Drag with lower compression heads?
    By Hank W in forum Technical Discussion
    Replies: 10
    Last Post: 08-15-2013, 12:02 PM
  4. Replies: 8
    Last Post: 11-27-2012, 07:21 PM
  5. Lower Compression after rebuild AND Low Water temp
    By mattyc in forum Technical Discussion
    Replies: 10
    Last Post: 10-24-2004, 09:34 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Frank Mole Transport