Compression Test Numbers

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MaineBoy

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I just had a compression check done a 1998 Yamaha 175 TXR Salrwater Series.

It came back with the following cylinder readings

1. 120
2. 120
3. 120
4. 120
5. 115
6 120

I am told these are very strong numbers....just wanted to ask opinions from folks who know before I sign oin the dotted line. The engine is on a 1999 209 that I put a deposit on. Are these numbers as good as I think they are?
 
Hey Maine Boy,
I just went through a repower and spending way too much time looking at many different engines. I'm not a mechanic but those numbers look good. Every mechanic I did speak with said that as long as your results come back within a 10% range they're good. I've also had a few say 5%. To really make sure you could have them do a leak down test as part of the final acceptance.
Good luck and happy boating!
 
What is the manufacturers range?

My 1995 200 HP salt water series ran at 115 - 125 which was in range for 12 years.


Make sure that the test was run hot with wide open throttle.
 
The numbers look good to me. Our 1995 175 SWS came in at all between 120 and 125 last time we checked.
 
thanks for the replies. Looking forward to getting this baby out on the water!
 
Tashmoo said:
What is the manufacturers range?

My 1995 200 HP salt water series ran at 115 - 125 which was in range for 12 years.


Make sure that the test was run hot with wide open throttle.
Click to expand...

How can you have a compression test at WOT ?
 
NOTHING ELSE MATTERS said:
Tashmoo said:
What is the manufacturers range?

My 1995 200 HP salt water series ran at 115 - 125 which was in range for 12 years.


Make sure that the test was run hot with wide open throttle.
Click to expand...

How can you have a compression test at WOT ?
Click to expand...

You advance the throttle handle to the wide open position prior to doing the test.
 
The right way to do compression checks ( different on 2 and 4 strokes also!)


all plugs out!!!!
safety lanyard pulled

Cold
Hot
Wet

2 strokes really do not need the throttle at WOT, its a 2 stroke!!! it still grabs air from the exhaust side

4 strokes i recommend a leak down test, not compression
you can still do a compression to get a OK reading
 
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