mercury 150 black max crank leak test

bassfisher21

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Oct 24, 2012
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Hi i have a mid 1990s 150 black max i would like to know the condition of my crank seals on can anyone tell me how to test them and how to go about this test?
 

Faztbullet

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Mar 2, 2008
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Re: mercury 150 black max crank leak test

What problems are you having?
 

bassfisher21

Recruit
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Oct 24, 2012
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Re: mercury 150 black max crank leak test

it has a studer in it once and awile its not bad at all just really want to knoew the condition of the seals cause of its age and it was sitting a wile before i stared usiing it so just want to make sure there good hate to wreck it cause of them it has 120 to 125 on all 6 for a 1990s motor i say thats good.
 

CharlieB

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Apr 10, 2007
Messages
5,617
Re: mercury 150 black max crank leak test

If compression is good then most likely the motor has always had enough oil in the mixture that the crank seals between cyls are also good.

Crank end seals can dry from extended periods of none use, but there you may still see a slight drop in compression on the end cyls.

An intermittent cyl misfire can be caused by a variety of things, from a dirty carb to failing ignition to a fouling spark plug to a clogged oil recirc hose/fitting.
 

Faztbullet

Supreme Mariner
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Mar 2, 2008
Messages
15,589
Re: mercury 150 black max crank leak test

If the crankcase seal rings(steel) are worn it will "cross talk" between cylinders at a idle. Could be a rectifier/stator as I have seen them act like a rev limiter and miss....
 

CharlieB

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Apr 10, 2007
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5,617
Re: mercury 150 black max crank leak test

Diagnosing your problem should be done in a logical manner, start with a simple spark test. Each plug wire should carry a hot blue arc across a 7/16 inch gap.

Disconnect the rectifier and Ohm test each yellow lead to the Red lead, then reverse your meter leads and repeat both tests. You should find continuity in one direction and nothing when reversed.

If both of these tests pass, then a DVA test of the stator high speed windings should be done to ensure sufficient voltage at speed.

Verify all plug wires are in good shape, no cracked insulation, loose connections, and that all coils have good clean, tight connections, no cracks in the coils.

Never assume any electrical parts is bad and start replacing things without first inspecting and testing to verify the fault. There is NO RETURN on electrical parts.
 

Dukedog

Captain
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Oct 6, 2009
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3,235
Re: mercury 150 black max crank leak test

it has a studer in it once and awile its not bad at all just really want to knoew the condition of the seals cause of its age and it was sitting a wile before i stared usiing it so just want to make sure there good hate to wreck it cause of them it has 120 to 125 on all 6 for a 1990s motor i say thats good.

Look elsewhere like suggested. Sealing rings won't "come n go" if they are weak. On just about any V6 from 1976 up they would be at tha very bottom of any list causin' a problem........jmo
 
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