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90 HP OMC OB idling issue

J

johnnyc2024

New member
It cranks over fine but can't maintain an idle. Can I bypass the VRO and primer systems by feeding the carbs directly w/ a gravity-fed & engine vaccuum-fed 50:1 fuel source/set-up....or do I need to at least utilize the VRO's fuel pump for pressurization of my separate 50:1 fuel source?
 
Model # of this motor ?----The VRO can be used to just pump mixed fuel.-----Your best bet is to take the first step in trouble shooting.-----Post the actual values you get from a compression test.
 
OB is a 1996 OceanRunner, J90SLEDA. I re-built & installed its 4 carbs because I thought that would be the cure for poor engine performance...haven't had it running/idling successfully since. Haven't tuned the idle mixture needle valve screws (on these rebuilt carbs) yet because I wasn't able to get it idling.

I will check compression values and re-post values soon. thanks!
 
racerone said:
Model # of this motor ?----The VRO can be used to just pump mixed fuel.-----Your best bet is to take the first step in trouble shooting.-----Post the actual values you get from a compression test.
Click to expand...
I'll look into routing remote 50:1 fuel source into VRO pump - thanks!
Range of compression pressure values for the four cylinders is 25-40 psi - acquired by manually turning flywheel bolt, on top of motor, clockwise, multiple rotations for ea cylinder's testing.
 
racerone said:
Model # of this motor ?----The VRO can be used to just pump mixed fuel.-----Your best bet is to take the first step in trouble shooting.-----Post the actual values you get from a compression test.
Click to expand...
I finally got back to getting compression values for the 4 cylinders. I cranked the starter motor using key - for about 1 sec for ea trial, 3 trials per cylinder...analog gauge 'holds' on max comp pressure experienced during the 1 sec trial. Ave of 3 max compression values (in psi) for ea cylinder for port top, port bottom, stbrd top, & stbrd bottom, are as follows: 139, 130, 135, & 127, resp.

further trouble-shooting & guidance would be much appreciated....

thanks!
 
racerone said:
You need to crank it over with the starter motor to get meaningful results.
Click to expand...
I finally got back to getting compression values for the 4 cylinders. I cranked the starter motor using key - for about 1 sec for ea trial, 3 trials per cylinder...analog gauge 'holds' on max comp pressure experienced during the 1 sec trial. Ave of 3 max compression values (in psi) for ea cylinder for port top, port bottom, stbrd top, & stbrd bottom, are as follows: 139, 130, 135, & 127, resp.

further trouble-shooting & guidance would be much appreciated....

thanks!
 
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