Mercury 115hp 1987 fuel pump inop help

Thomas coe

Seaman Apprentice
Joined
Jul 6, 2015
Messages
38
That's what I figured last night I took it apart and cleaned it.and put just a touch of rtv on the screw holes and I let it sit over night when I get home gonna see what we got
 

DavidMoore

Petty Officer 2nd Class
Joined
Jun 2, 2015
Messages
183
If there was a clogs how would I have got fuel to the pump?

Because the power you can exert with your hand on the primer bulb is way more than your fuel pump can produce.

You described the collapsed primer bulb condition below.

credits to continuouswave.com Primer Bulb As Diagnostic Tool

The primer bulb is also a diagnostic tool that will tell you a number of things about your fuel system.
Engine Stalling or Running Roughly at Speed

If your engine begins to stall or run roughly several minutes after starting and when running at higher speeds, use the primer bulb to force fuel to the engine. If this restores the engine to smooth running, you have a fuel supply problem. There may be a restriction in the fuel line, or your engine fuel pump could be defective. If this happens even at idle speeds, the primer bulb may not be working properly.
Primer Hard to Prime

If the fuel line is difficult to prime, you likely have an air leak in the system. Check all fuel hose connections. You could also have a defective primer bulb, or not be orientating the primer bulb properly during priming. A likely place to investigate is the fuel disconnect on the engine. Be sure the connector is properly seated and is making an air-tight connection.
Collapsed Primer Bulb

If the primer bulb collapses after the engine has been running or stays collapsed while priming this indicates a fuel line restriction upstream from the primer bulb. A defective check valve in the primer bulb could also be the cause. The fuel line filter or the fuel tank pick up could be blocked. A blocked fuel tank vent could also cause this. A quick way to check the tank venting is to temporarily open the fuel tank filler fitting. For some reason the fuel tank vent line thru-hull fitting is a favorite spot for wasps to build mud nests.
Primer Bulb Never Gets Firm

If you can fill the bulb with fuel but it never gets firm, you probably have a fuel leak downstream of the primer bulb. This could be a stuck float valve on a carburetor, or a fuel leak in the engine fuel pump. Many engines use a diaphragm pump, and if the rubber diaphragm has a pin hole leak, gasoline will be forced past it into the engine crankcase. It should only take a few squeezes to get a primer bulb to become firm.
If you have a fuel disconnect downstream of the primer bulb, disconnect the fuel line from the engine and see if the primer can now be pumped to firmness. If so, your leak is in the engine.
Primer Bulb Gets Soft While Engine Is Running

Most primer bulbs will lose some firmness when the engine is running. This is normal. The bulb should not run dry of fuel or collapse in suction, but it will tend to lose some of the hard firmness it had when initially primed.
 
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Thomas coe

Seaman Apprentice
Joined
Jul 6, 2015
Messages
38
Motor runs I cleaned the motor surface last night and put some sealant on the screw holes and took the fuel tank connector off and stuck it directly into the tank motor ran great.
 

Thomas coe

Seaman Apprentice
Joined
Jul 6, 2015
Messages
38
Another question when I rebuild the carbs what should I put on all the screws to asure that they will not leak I see some sort of red sealant but I don't think it is lock tight thanks for the help
 

GA_Boater

Honorary Moderator Emeritus
Joined
May 24, 2011
Messages
49,038
All the screws should be through gaskets, so no sealant is needed.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,733
Tom, Are you asking about the brass plugs on the carb? The factory used some sort of red sealant. Clean off that stuff, and when reinstalling the plugs, make them tight and smear some silicone over them. Just a touch is all you need.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,733
Actually silicone stands up to gasoline, after it has hardened. Permetex #2 and #3 dissolve in gasoline, even after a long while. You could use nail polish as well.
 
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