Jump to content

Welcome to TheMalibuCrew!

As a guest, you are welcome to poke around and view the majority of the content that we have to offer, but in order to post, search, contact members, and get full use out of the website you will need to Register for an Account. It's free and it's easy, so don't hesitate to join the TheMalibuCrew Family today!

Sign in to follow this  
Bedford5MXZ

Compression test results

Recommended Posts

Bedford5MXZ

I am hopefully picking up a 2012 22 MXZ boat next week but I am a little concerned about the compression test I got back today.  Wanted to throw it on here and see what you guys think?  The boat has the standard Monsoon 350 in it 

#1 - 190

#2 - 195

#3 - 185

#4 - 205

#5 - 200

#6 - 185

#7 - 210

#8 - 200

Share this post


Link to post
hawaiianstyln

who did the test?  They aren't way off but they could be if the test was not done exactly right

Share this post


Link to post
hawaiianstyln
Posted (edited)

correct way:

https://www.m2omarine.com/fckimages/pdf/ENGINE/02.pdf

Compression Test Procedure

1.Charge the battery if the battery is not fully charged.

2. Disable the ignition system.

3. Disable the fuel injection system.

4. Remove all the spark plugs.

5. Block the throttle plate wide open.

6. Start with the compression gauge at zero, and crank the engine through four compression strokes

(four puffs).

7. Make the compression check for each cylinder. Record the reading.

8. If a cylinder has low compression, inject approximately 15 ml (one tablespoon) of engine oil into

the combustion chamber through the spark plug hole.

Recheck the compression and record the reading.

9. The minimum compression in any one cylinder should not be less than 70 percent of the highest

cylinder. No cylinder should read less than 690 kPa (100 psi). For example, if the highest pressure in

any one cylinder is 1035 kPa (150 psi), the lowest allowable pressure for any other cylinder would

be 725 kPa (105 psi). (I035 x 70% = 725) (150 x 70% = 105).

NOTE: Compression in a brand new engine will only read about 60 psi until the rings have

seated.

•Normal - Compression builds up quickly and evenly to the specified compression for each

cylinder.

•Piston Rings Leaking - Compression is low on the first stroke. Compression then builds up

with the following strokes but does not reach normal. Compression improves considerably

when you add oil.

•Valves Leaking - Compression is low on the first stroke. Compression usually does not build

up on the following strokes. Compression does not improve much when you add oil.

•If two adjacent cylinders have lower than normal compression and injecting oil into the

cylinders does not increase the compression; the cause may be a head gasket leaking

between the cylinders.

Edited by hawaiianstyln

Share this post


Link to post
Bedford5MXZ

Was done at a dealership so can only assume it was done correct?  Was concerned with a high of 210 and low of 185.  Is that to far off?  Should I be concerned? They did not seem to be but is that because they don’t want to go through the motor?  

Share this post


Link to post
dwc032

I just had mine done, same engine with over 715 hours. I think Compression was right about 200 each cylinder.  I will find the sheet from the dealer and confirm. 

Share this post


Link to post
SkiPablo
1 hour ago, Bedford5MXZ said:

Was done at a dealership so can only assume it was done correct?  Was concerned with a high of 210 and low of 185.  Is that to far off?  Should I be concerned? They did not seem to be but is that because they don’t want to go through the motor?  

those numbers are both fine

Share this post


Link to post
MLA
1 hour ago, Bedford5MXZ said:

Was concerned with a high of 210 and low of 185.  Is that to far off?

Its close to the recommended base line. IMO, it would warrant doing the test again, just to see if the % difference stayed about the same, or changed. 

Share this post


Link to post
roeboat
4 hours ago, Bedford5MXZ said:

Was done at a dealership so can only assume it was done correct?  Was concerned with a high of 210 and low of 185.  Is that to far off?  Should I be concerned? They did not seem to be but is that because they don’t want to go through the motor?  

I wouldn't be so sure.  When we bought our boat we had the dealer do a compression test and it came back good. The problem was they didn't disable the fuel injection so the cylinders were flooded and the engine needed new plugs and an oil change. They are reputable dealer just made a mistake.

Share this post


Link to post
COOP

Nothing about those numbers would worry me. 

Were these taken cold? After winter storage?

We usually run the motor first to warm it up. Then let it cool down a bit and do the test. Many times the lower numbers will then come up. 

Ideally you want a 10% variance between the highest and the lowest.

Share this post


Link to post
Steve B.

Numbers look pretty good. Lake test that bad boy. 

Steve B. 

 

Share this post


Link to post
Bedford5MXZ

So called Malibu today to talk with technical and they said that the older Monsoon motors were a 20% variance.  So I will run with it and lake test next week!  Looking forward to a new used MXZ in the lift this summer!  Thanks for all the feed back.  

Share this post


Link to post
electricjohn

You never mentioned hrs. on the motor

Share this post


Link to post

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...