'95 Sportjet 120xr- flooding

[Christo680]

The bottom cylinder on my '95 sportjet 120 (force) fills with gas after sitting for short periods of time, hydro-locking the motor. I pull the plug and drain the cylinder and it starts right up. The boat (Sea Rayder F-14) has an electric fuel pump between the fuel tank and motor. I am not sure if this pump is standard on this boat or if it was added by a previous owner. I suspect the electric pump if over pressurizing the needle valves in the carbs, causing the flooding. Any thoughts or suggestions would be greatly appreciated. Thanks in advance!

 

[racerone]

Is the factory installed fuel pump still there ?

 

[Redbarron%%]

The electric pump is for priming only, the engine driven pump should be delivering the fuel to the carbs when it is running.
The max fuel pressure should be around 6 PSI and you might be higher if you have both pumps running.
The primer should be on a momentary contact switch.

 

[Christo680]

Factory pump is there- it appears that the electric pump is on the ignition switch and not the "start" position. I will have to verify that. Also, it has been working fine, this started happening at the end of the season. Thanks

 

[Redbarron%%]

You may have a broken diaphragm in the engine driven fuel pump that is letting the electric pump push fuel into the lower cylinder.
I have used the electric pup along with the engine driven pump on my Sport jet with no ill effect, but the engine driven pump should be sufficient by it's self and if you run both pumps all of the time then if one were to fail yu would keep running with no backup from the other pump.
The XR has the fuel enrichment valve and would not have a start switch choke switch when the key was pushed in.
Perhaps someone wired in the electric pump after the boat was built?

 

[jerryjerry05]

The electric motor is standard on the sport jets.
Takes the place of the squeezie.
It's also supposed to have a switch to kill it once pressure is reached
or the motor starts.

The fuel in the lower cyl. Sounds like the needle/seat or float needs work?
The regular pumps pressure is 2-3# and the needle/seat should be able to hold that
all day long.

Filling the cyl. enough to cause hydro lock??
How much fuel?

 

[Christo680]

I will check the engine driven pump, as well as the wiring on the electric pump. My original thought was the electric pump was on all the time and it wasn't a problem until recently. I'm now leaning toward the needle valves and see a carb rebuild over the winter,if both pumps check out. And yes, it was hydro-locked (or fuel locked)-- there was enough gas in the cylinder to soak the transom & bilge when I pulled the spark plug (1/4 cup??!!!). Thanks everyone for the info. -will let you know how I make out.

 

[Redbarron%%]

I would suspect that if the needle valve were leaking there would fuel leaking from the front of the carb as well as running out into the bilge (ask me how I know).
Not that cleaning the carbs is not a good thing to do.
Since the engine driven fuel pump can feed fuel directly to the lower cylinder I would suspect that the diaphragm is leaking instead of the carb as the electric pump will happily pump the lower cylinder full of gas through the engine driven pump diaphragm.
This is one reason to not have an electric pump running as a matter of course in the boat. If you have a leak instead fo starving the engine for fuel (sucking air at the source of the lead due to the vacuum pulling the fuel to the engine) the electric pump will push it out into the bilge where...

 

[Christo680]

Thanks Redbarron - will check mechanical pump before I tear into carbs, hopefully this weekend. (actually no rush now, done for the season) will post my findings, and thanks Everyone for the help!