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1994 Mercury Blackmax 175 hard to start issue

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Wilderthanmost912

New member
I have this outboard that it is in really good shape we bought used that hasn't been in the water for 3 years. I rebuilt all 3 carbs, rebuilt the fuel pump, replaced all of the fuel lines, spark plugs and replaced the internal fuel tank with an exact dimension custom built fuel tank. Motor ran great at first in the yard, but has been sitting in the yard for a few months while we rewired the entire boat and console. Including install of new controls, Racor water separator and tank vent fitting (through hull). Now motor is hard to start and once started, is not running on all 6 cylinders. Recently noticed that we had a primer bulb and external fuel line failure so replaced it, but still not idleing or running properly. Checked compression when purchased motor and again recently with a 130psi reading which is good, so I'm told. We also have installed a fuel surge protection valve on the tank vent to prevent fuel spillage into the water, which we checked and is working as designed. Primer bulb isn't collapsing so it seems to be working properly. Any suggestions as to what could cause the hard to start, missing and not idleing problem? Gonna replace new spark plugs again tomorrow and test again but not feeling positive so looking for advice.

Regards,

frustrated mako owner
 
Wilderthanmost, You mentioned it ran fine in yard,no load on engine,in neutral,really means nothing here. Plugs might tell us something,running lean, rich,etc. Try removing fuel/water separator,pouring contents into a clear glass container,let sit overnight to see if it separates, Water,gunk left behind from old fuel system. With engine running do a cylinder drop test,pulling one wire at a time,observing tachometer for drop of rpms, Also place timing light on same to see what is getting spark and what isn't. Has a open air gap spark test been run? A big blue lightning snap should be seen and heard. While engine is "running" try pumping primer bulb to see if issue subsides,thus showing a fuel restriction or a possible weak or defective fuel pump
 
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