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Jan 23rd, 2013
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Low hour, low compression motor #12646634
02/26/18 12:30 AM
02/26/18 12:30 AM
Joined: Feb 2018
Posts: 4
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Drobe0711 Offline OP
Green Horn
Drobe0711  Offline OP
Green Horn
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Joined: Feb 2018
Posts: 4
I am looking at a 2010 boat with a 150 Mercury Optimax. The motor has less than 200 hours on it with over half of that idling/trolling/low rpm. The engine report showed that all cylinders had 95 psi compression. This less than the service manual that say 110 - 130 psi for compression. All the mechanics I have talked too said that since the cylinders were even, that it is ok. Is it more likely for a low hours motor to have low compression/stuck or worn rings or that the test was done cold?

Re: Low hour, low compression motor [Re: Drobe0711] #12646683
02/26/18 12:55 AM
02/26/18 12:55 AM
Joined: Jan 2005
Posts: 6,052
Seadrift TX
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Pat Goff Online content
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Pat Goff  Online Content
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Joined: Jan 2005
Posts: 6,052
Seadrift TX
Probably cold motor.


Pat Goff
Seadrift TX
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Re: Low hour, low compression motor [Re: Drobe0711] #12646843
02/26/18 02:07 AM
02/26/18 02:07 AM
Joined: Jul 2011
Posts: 1,174
Port Isabel/SPI
Capt. Andrew Offline
Extreme Angler
Capt. Andrew  Offline
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Joined: Jul 2011
Posts: 1,174
Port Isabel/SPI
I had a motor test at 99lbs with one gauge and 130 with another. As long as they are all around 10% of each other and the motor runs smooth its goo.


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Snook,Redfish,Trout Fishing South Padre Island, Texas.
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Re: Low hour, low compression motor [Re: Drobe0711] #12647515
02/26/18 04:24 PM
02/26/18 04:24 PM
Joined: May 2003
Posts: 11,494
Littlefield Tx & Lake A. H. US...
gary purdy Offline
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gary purdy  Offline
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Joined: May 2003
Posts: 11,494
Littlefield Tx & Lake A. H. US...
Do a carbon cleaning on it.


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
Re: Low hour, low compression motor [Re: Drobe0711] #12647608
02/26/18 05:19 PM
02/26/18 05:19 PM
Joined: Apr 2015
Posts: 1,667
Grand Prairie Tx
Curtbass Online content
Extreme Angler
Curtbass  Online Content
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Joined: Apr 2015
Posts: 1,667
Grand Prairie Tx
Check it usung another gauge just to see if there are different results. Then de carbon motor & do it again. Warm motor up, check with throttle in wide open position, for initial readings then do a leakdown test. A more comprehensive picture of motor health.
I would be leery about the lower results but hate to see someone miss a fair deal in a good even motor over a faulty gauge. Ask seller if hes willing to do that. Could benefit both of you. He makes a sale & you make a better purchasing decision.

Last edited by Curtbass; 02/26/18 05:26 PM.

92' ChampioN 201DCR Elite
13' Yamaha250SHO
Re: Low hour, low compression motor [Re: Drobe0711] #12648104
02/26/18 09:50 PM
02/26/18 09:50 PM
Joined: Nov 2002
Posts: 3,741
Yantis, TX
Gamblinman Online content
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Gamblinman  Online Content
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Posts: 3,741
Yantis, TX
Along with the above, you need to perform a leak down test to determine the actual condition of cylinder sealing.

Last edited by Gamblinman; 02/26/18 09:51 PM.
Re: Low hour, low compression motor [Re: Curtbass] #12648412
02/27/18 01:24 AM
02/27/18 01:24 AM
Joined: Apr 2015
Posts: 1,667
Grand Prairie Tx
Curtbass Online content
Extreme Angler
Curtbass  Online Content
Extreme Angler

Joined: Apr 2015
Posts: 1,667
Grand Prairie Tx
i mentioned leakdown test also.


92' ChampioN 201DCR Elite
13' Yamaha250SHO
Re: Low hour, low compression motor [Re: Drobe0711] #12649112
02/27/18 02:48 PM
02/27/18 02:48 PM
Joined: Feb 2018
Posts: 4
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Drobe0711 Offline OP
Green Horn
Drobe0711  Offline OP
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Joined: Feb 2018
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Thanks everybody for the suggestions. I was planning on having a leak down test completed when I went to look at the boat. I will ask the current owner if he can have a carbon cleaning done.

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