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#12544370 - 12/19/17 08:15 PM Compression Report Thoughts
TexasTechsan Offline
Outdoorsman

Registered: 02/24/10
Posts: 59
Loc: Argyle, TX
I'm looking at a boat that has a 2014 250 SHO on it. I had the seller take it in to get a compression test done.
Below are the readings. I always have used the rule of thumb where readings should be no more than 10% of each other.
This report shows a larger variance than id like but the mechanic stated its within spec and variance was caused by fogging oil present. Thoughts?



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#12544529 - 12/19/17 10:27 PM Re: Compression Report Thoughts [Re: TexasTechsan]
TexasTechsan Offline
Outdoorsman

Registered: 02/24/10
Posts: 59
Loc: Argyle, TX
I'm having the seller get the test again after I test drive the boat. That should burn off the fogging oil and the test readings should be accurate. How worried would you all be after seeing the initial compression report? Is it truly within spec, like the tech noted, with readings of 160psi-180psi?
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#12544623 - 12/20/17 05:43 AM Re: Compression Report Thoughts [Re: TexasTechsan]
tmd11111 Online   content
Extreme Angler

Registered: 04/30/17
Posts: 1053
Loc: San Angelo
To do a proper compression test the tech should have ran the motor up to operating temperature first. This would have burned off all fogging oil and gave a true reading.

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#12544628 - 12/20/17 05:57 AM Re: Compression Report Thoughts [Re: TexasTechsan]
Cat finder Offline
Angler

Registered: 03/14/15
Posts: 455
Loc: Dallas, Texas
This^^^
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#12544675 - 12/20/17 07:24 AM Re: Compression Report Thoughts [Re: TexasTechsan]
gary purdy Offline
TFF Guru

Registered: 05/24/03
Posts: 11484
Loc: Littlefield Tx & Lake A. H. US...
I am concerned about the motors abuse. 6984 rpm`s for 10.6 min. and over-rev-count for 51.6 min. Like already said the motor should have been run before the compression test. Any oil in a cylinder will normally make the cylinder show higher compression. This motor doesn`t have a lot of factory warranty left. I will add that Yamaha has been really good at taking care of these SHO motors even when problems occur just out of warranty.
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The world will not be destroyed by those who do evil, but by those who watch them without doing anything. Remember what He has done and remember that He is not done yet!-- GOD IS GOOD

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#12544733 - 12/20/17 08:16 AM Re: Compression Report Thoughts [Re: tmd11111]
TexasTechsan Offline
Outdoorsman

Registered: 02/24/10
Posts: 59
Loc: Argyle, TX
Originally Posted By: tmd11111
To do a proper compression test the tech should have ran the motor up to operating temperature first. This would have burned off all fogging oil and gave a true reading.
I agree and that's why I'm having the seller take it back up to get it looked at again. Seems like poor workmanship not to 're run the test correctly before writing up the report. Thanks for the reply!
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#12544735 - 12/20/17 08:18 AM Re: Compression Report Thoughts [Re: gary purdy]
TexasTechsan Offline
Outdoorsman

Registered: 02/24/10
Posts: 59
Loc: Argyle, TX
Originally Posted By: gary purdy
I am concerned about the motors abuse. 6984 rpm`s for 10.6 min. and over-rev-count for 51.6 min. Like already said the motor should have been run before the compression test. Any oil in a cylinder will normally make the cylinder show higher compression. This motor doesn`t have a lot of factory warranty left. I will add that Yamaha has been really good at taking care of these SHO motors even when problems occur just out of warranty.
I noticed that in the report but thought something wasn't right because in the RPM/Hour section of the report it says that the engine has nobhours between 6,000-7,000 toms. Something looked off about all of it.
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#12545022 - 12/20/17 11:25 AM Re: Compression Report Thoughts [Re: TexasTechsan]
tmd11111 Online   content
Extreme Angler

Registered: 04/30/17
Posts: 1053
Loc: San Angelo
Originally Posted By: TexasTechsan
Originally Posted By: gary purdy
I am concerned about the motors abuse. 6984 rpm`s for 10.6 min. and over-rev-count for 51.6 min. Like already said the motor should have been run before the compression test. Any oil in a cylinder will normally make the cylinder show higher compression. This motor doesn`t have a lot of factory warranty left. I will add that Yamaha has been really good at taking care of these SHO motors even when problems occur just out of warranty.
I noticed that in the report but thought something wasn't right because in the RPM/Hour section of the report it says that the engine has nobhours between 6,000-7,000 toms. Something looked off about all of it.




According to the report i has 51 minutes over 6000 rpms. Report in rpm increments is by hours. 9 more minutes over 6k and it will show 1 hour. Gotta wonder as to why or how it was rev'd to almost 7k rpms though.

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#12545071 - 12/20/17 11:51 AM Re: Compression Report Thoughts [Re: TexasTechsan]
boatman025 Offline
Pro Angler

Registered: 07/16/10
Posts: 563
Loc: Wylie
Have them do a leak down on motor on a 4stroke that tells you more than compression will those motor are made to run over 6000
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Wylie ,Texas

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#12545098 - 12/20/17 12:18 PM Re: Compression Report Thoughts [Re: tmd11111]
TexasTechsan Offline
Outdoorsman

Registered: 02/24/10
Posts: 59
Loc: Argyle, TX
Originally Posted By: tmd11111
Originally Posted By: TexasTechsan
Originally Posted By: gary purdy
I am concerned about the motors abuse. 6984 rpm`s for 10.6 min. and over-rev-count for 51.6 min. Like already said the motor should have been run before the compression test. Any oil in a cylinder will normally make the cylinder show higher compression. This motor doesn`t have a lot of factory warranty left. I will add that Yamaha has been really good at taking care of these SHO motors even when problems occur just out of warranty.
I noticed that in the report but thought something wasn't right because in the RPM/Hour section of the report it says that the engine has nobhours between 6,000-7,000 toms. Something looked off about all of it.




According to the report i has 51 minutes over 6000 rpms. Report in rpm increments is by hours. 9 more minutes over 6k and it will show 1 hour. Gotta wonder as to why or how it was rev'd to almost 7k rpms though.
That makes sense about it not reading 1 full hour yet at 6000+rpms. Wonder why the other rpm ranges have the decimal point but under 1000 and over 6000 do not? Im concerned about the high rpm as well. I'm working to get an answer.
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#12545101 - 12/20/17 12:20 PM Re: Compression Report Thoughts [Re: boatman025]
TexasTechsan Offline
Outdoorsman

Registered: 02/24/10
Posts: 59
Loc: Argyle, TX
Originally Posted By: boatman025
Have them do a leak down on motor on a 4stroke that tells you more than compression will those motor are made to run over 6000
I'll ask to get this leak down test done. I would have been as concerned had the boat been run at 6000-6200rpms but almost 7k makes me iffy on the deal. Thanks for the recommendation.
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#12546977 - 12/21/17 07:46 PM Re: Compression Report Thoughts [Re: TexasTechsan]
gary purdy Offline
TFF Guru

Registered: 05/24/03
Posts: 11484
Loc: Littlefield Tx & Lake A. H. US...
Limiter is 6250. Yamaha recommends you run the SHO at higher RPMs on top and be propped correctly. Ideally 5800-6000 at WOT. Bearing failures have occurred due to under propped rigs putting the motor in a strain. Found this out yesterday from Yamaha and my Yamaha Master Technician.
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The world will not be destroyed by those who do evil, but by those who watch them without doing anything. Remember what He has done and remember that He is not done yet!-- GOD IS GOOD

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#12547345 - 12/22/17 06:21 AM Re: Compression Report Thoughts [Re: gary purdy]
tmd11111 Online   content
Extreme Angler

Registered: 04/30/17
Posts: 1053
Loc: San Angelo
Originally Posted By: gary purdy
Limiter is 6250. Yamaha recommends you run the SHO at higher RPMs on top and be propped correctly. Ideally 5800-6000 at WOT. Bearing failures have occurred due to under propped rigs putting the motor in a strain. Found this out yesterday from Yamaha and my Yamaha Master Technician.


Got that backwards. Under propped will let the motor over rev with little strain. Over propping will put a strain on the motor due to not being able to reaching optimal rpm range.

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#12547532 - 12/22/17 08:44 AM Re: Compression Report Thoughts [Re: tmd11111]
gary purdy Offline
TFF Guru

Registered: 05/24/03
Posts: 11484
Loc: Littlefield Tx & Lake A. H. US...
Originally Posted By: tmd11111
Originally Posted By: gary purdy
Limiter is 6250. Yamaha recommends you run the SHO at higher RPMs on top and be propped correctly. Ideally 5800-6000 at WOT. Bearing failures have occurred due to under propped rigs putting the motor in a strain. Found this out yesterday from Yamaha and my Yamaha Master Technician.


Got that backwards. Under propped will let the motor over rev with little strain. Over propping will put a strain on the motor due to not being able to reach optimal rpm range.
This is relating to high RPM`s causing premature bearing failure. Straining caused from over propping causes piston failure.
_________________________
The world will not be destroyed by those who do evil, but by those who watch them without doing anything. Remember what He has done and remember that He is not done yet!-- GOD IS GOOD

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#12547777 - 12/22/17 11:15 AM Re: Compression Report Thoughts [Re: TexasTechsan]
boatman025 Offline
Pro Angler

Registered: 07/16/10
Posts: 563
Loc: Wylie
bump Gary P
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Wylie ,Texas

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