Logo
FULL SITE MENU

3.0 OMC Inboard bogs please help

Did you check:
Anti siphon valve
Fuel pick up tube for crud build up if it has a screen on the end of it as some do?
Fuel tank vent
Fuel line from tank to pump?
 
The thing to keep in mind is that there are 2 separate systems, the engine fuel system and the boat fuel system (what I listed above). If only focusing on the engine fuel system, you can miss the actual cause.
other tests that can be done:
clear hose test, use a length of clear fuel hose in between the hose that comes from the tank (use a double barb fitting) and the fuel filter inlet. Run the engine and see if you see a steady stream of bubbles. If so air is getting pulled in, it could be a bad fuel line or even a crack in the fuel pick up tube.
fuel line vacuum test that can be done:
measuring the vacuum in the fuel line between the tank and the pump, this is more complex to do, you need a vacuum gauge and it has to be teed into a fuel line that gets connected between the line running from the tank to the fuel filter inlet. If the vacuum is higher than about 4" of mercury, you have a restriction, that could be a bad anti siphon valve or crud on the screen on the pick up tube if there is one.

it sounds like your fuel pump is OK, there is one last test you can do, disconnect the fuel line from the tank to the fuel filter inlet and hook up a vacuum gauge to it. Start the engine, a healthy pump will pull at least 9-10" of mercury on the gauge. Note that this is different than the fuel line vacuum test above.

when doing any of these tests be sure to be cautious about fuel vapors!
 

HOW TO: Testing your boats fuel system.

Note, this was originally posted courtesy of Don S. Minor edits and pictures added by CaptJason A lot of you folks out there seem to be tearing into carbs quite a bit. Before you choose to open up a carb, you really need to look at what's feeding the carb first, and that is the boats fuel...
forums.iboats.com forums.iboats.com

see this thread, it explains it well, just be careful with made-up fuel line connections, watch for leaks when testing!
 
I set the timing to 4* BTDC
Could not get the dwell close to 31-34 unless I almost had the points closed
Tried another set of new points and set them to 0.019”
And dwell remained about 24*, I think it may be my meter!
Still can’t get it to run better
Will stall unless I keep my rpm up about 1000
I have to try disconnecting the gray wires to by pass the esa I’m pretty sure I did it like you said but want to try again in case I didn’t.
I have 15-18 inches of mercury vacume at the big plug on the bottom of the carb by the throttle plates
I pulled the plugs out and re checked the compression after it was warmed up I have 135-145
Plugs are black so it’s over fueling
Adjusted the air needles on the carb
Best I could make it run is about 3-4 turns out which is too much
I have ac delco plugs in there they are the correct number and the marine application
Don’t have the number at the moment but I’ve always had good luck with ac plugs
 
louc said:
Did you check:
Anti siphon valve
Fuel pick up tube for crud build up if it has a screen on the end of it as some do?
Fuel tank vent
Fuel line from tank to pump?
Click to expand...
New anti syphon valve
New fuel lines
No sock/filter on the pick up tube in the tank
And the vent is clean and air moves freely
 
louc said:
The thing to keep in mind is that there are 2 separate systems, the engine fuel system and the boat fuel system (what I listed above). If only focusing on the engine fuel system, you can miss the actual cause.
other tests that can be done:
clear hose test, use a length of clear fuel hose in between the hose that comes from the tank (use a double barb fitting) and the fuel filter inlet. Run the engine and see if you see a steady stream of bubbles. If so air is getting pulled in, it could be a bad fuel line or even a crack in the fuel pick up tube.
fuel line vacuum test that can be done:
measuring the vacuum in the fuel line between the tank and the pump, this is more complex to do, you need a vacuum gauge and it has to be teed into a fuel line that gets connected between the line running from the tank to the fuel filter inlet. If the vacuum is higher than about 4" of mercury, you have a restriction, that could be a bad anti siphon valve or crud on the screen on the pick up tube if there is one.

it sounds like your fuel pump is OK, there is one last test you can do, disconnect the fuel line from the tank to the fuel filter inlet and hook up a vacuum gauge to it. Start the engine, a healthy pump will pull at least 9-10" of mercury on the gauge. Note that this is different than the fuel line vacuum test above.

when doing any of these tests be sure to be cautious about fuel vapors!
Click to expand...
I will try these tests thank you
 
Back
Top