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45 HP Mercury Mariner dies underload.

J

jmlb444

New member
1989 45 HP mercury mariner I can idle perfect in my drive with ear muffs little rough to start at first once warmed up I can turn off and on I can shift gears in driveway no affect . On the water I can sometimes go no problems then after I turn it off it will start but die in gear with a little gas sometimes it dies in gear with a little gas right from the dock.I am getting spark on all 4 cylinders I have done a compression test I'm getting around 70 psi all the way around could this be the reason it dies in gear?
 
It will not run properly with 70 PSI. -------Or you have a bad gauge.-----It is NOT running perfectly in your driveway , it just sounds like it to you.------Test with another gauge or remove intake bypass covers to inspect pistons and rings.-----How did it run for you last month and what happened ?
 
racerone said:
It will not run properly with 70 PSI. -------Or you have a bad gauge.-----It is NOT running perfectly in your driveway , it just sounds like it to you.------Test with another gauge or remove intake bypass covers to inspect pistons and rings.-----How did it run for you last month and what happened ?
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In my drive it's a little rough to cold start but once its going it idles and runs fine I can shift gears nothing turn it off and starts right back up once warm. This all started two weeks ago at the lake I was cruising in towards the dock and it stalled and then I would start it and every time I gave it gas it would die reverse or forward it will idle on the water but as soon as it is in gear and a little gas dead.
 
Some will argue----It is NOT running fine on the trailer.------The motor even in gear is really still in neutral.-----The prop does not have to do any work spinning in air !------Sounds like it might be running on 3 cylinders or on it's last legs.------Yuo have tested the overheat horn ?----Replaced water pump impeller ?-----Mixing gas and oil at 50:1 ?
 
I don't know how to check the overheat horn but yes I have new impeller and 50-1 oil mix it pees water fine I just assumed it was cooling fine I really don't know what I'm doing.
 
1. Go to an Auto Zone store and borrow a compression tester.

2. Pull the plugs and take compression readings. Record them.

3. Report back.


Jeff
 
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