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Thread: 1984 Mariner 75 Compression
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11-23-2020, 10:34 AM #15000 RPM
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1984 Mariner 75 Compression
There is a 1984 Mariner 75hp I am getting ready to sell, that I think it is in great shape and it runs good. I went to do a compression check on it and the numbers all came up consistently between 175-185lbs. I considered this excellent, but now I'm wondering if this is too high. I did forget to open up the carbs when I tested, but I doubt that would make it go higher as opposed to lower. I'll try the test again, but does this sound normal?
The motor is 2/3's of a Tower of Power, it just has the 4 cylinders inline.
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11-23-2020, 10:43 AM #2
try another compression gauge..
Checkmate 2002 Convincor 270 496 MAG-HO
2003 Cougar 22MTR w/300xs SOLD
90 21Skater w/300xs - sold
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11-23-2020, 10:46 AM #3Screaming And Flying!
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Did you fog it up real good, if so run it clean and try again.
Maybe at some point someone slipped high domes in it too?Last edited by FMP; 11-23-2020 at 10:55 AM.
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11-23-2020, 07:29 PM #45000 RPM
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So I did try another compression gauge. That was a good idea, but the results was similar, so that is not the problem.
... and to answer the question about fogging, yes it had been fogged a while back for storage, and I sprayed a bit more just before testing because I worry about spinning a dry engine for fear of causing damage. This last time though after I spun it several times and cleared some of that oil out I started to get readings closer to 150. So I believe if I actually ran the engine first and then did a test I suspect it would show something more normal as mentioned.
Thanks for the tips guys.
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11-23-2020, 08:10 PM #5Screaming And Flying!
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So you still have room for the high domes
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