Jet Boat fuel problems after replacing switch box

[Dan Shaw]

Okay, looking for some advice. I have a 2000 Sugar Sands Tango with Mercury 175 Sport Jet Drive. Recently I was having trouble starting it and we traced the problem to the Switch Box. I replaced both Switch Boxes with new ones from CDI Electronics. This solved the issue with the spark plugs not igniting, however now I can't get fuel to flow to the engine.

• I have power to the main fuel pump (can't hear it, however I don't think it kicks on until the engine starts? Boat mechanic doesn't think fuel pump is bad).
• The starting fuel pump seems to be working, I can hear it pumping
• Engine runs fine if I pour fuel directly into it
• Didn't have any issues with fuel prior to replacing the switch box.

Question; could this be related to the Switch Box? Maybe a bad switch?

Would appreciate any help

 

[tdonoughue]

I don't know about that engine specifically, but I would certainly question the switch box. Do you still have the old one? How hard was the swap? Did you do it yourself? Might try the old one again and see if you get fuel (and no spark) or if there is no fuel or spark.

Separately, I have never heard of a fuel pump that waits until the engine starts to begin pumping. Sounds odd to me. Should pump immediately, I would think.

 

[Speedling]

Check fuel filter.
If it is an electric pump you can take the line off and see the fuel coming out to verify it's working. I don't know if that works with a carburetor setup but the pump if electric will work the same.

 

[Dan Shaw]

I don't know about that engine specifically, but I would certainly question the switch box. Do you still have the old one? How hard was the swap? Did you do it yourself? Might try the old one again and see if you get fuel (and no spark) or if there is no fuel or spark.

Separately, I have never heard of a fuel pump that waits until the engine starts to begin pumping. Sounds odd to me. Should pump immediately, I would think.

So, my mechanic friend was working on it with me and said he had to put cloth/sponges covering the carb intake (blocking air?) and it would run for a bit until the fuel in the carb ran out. So maybe something with the air pressure or air/fuel mix isn't right.

He took apart the carb and everything looked good. I thought he said the 2nd pump (main pump) was mechanical, not electric (anyone confirm). He also checked the fuel lines and blew them out with a compressor to check and everything looked good there.

We also switched back the switch boxes with the old ones and that wasn't it.

On another note, he called a boat mechanic that worked at the dealer for some advice and gave us some suggestions but said these engine designs are a pain in the as$ to work because they tried to take an outboard motor and combine it with a jet drive, so when you try to troubleshoot an out-drive you have to remember its a jet drive.

 

[Dan Shaw]

Check fuel filter.
If it is an electric pump you can take the line off and see the fuel coming out to verify it's working. I don't know if that works with a carburetor setup but the pump if electric will work the same.

What part/system controllers the fuel pump? Fuel filter was checked and nothing was wrong with it.

 

[jcyamaharider]

Just buy chance these do not have grey tempo lines for the fuel do they? If it does GET RID OF THEM! Replace with all new fuel lines that are ethanol fuel safe. I just had to do this to my 96 sea doo. It is a common issue that these fuel lines create this gunk and clog up lines and connection points.

 

[tdonoughue]

We also switched back the switch boxes with the old ones and that wasn't it.

So when you switched them, there was still no fuel? Then it was not the switch box that caused the issue.

Then you should be pulling the fuel line off. See what comes out as you crank. Bet you need a new fuel pump. Or two.

 

[Gym]

@Julian. possibly @Dan Shaw would get a better response if this thread were moved to the Sugar & Sands forum.

 

[Gym]

@Dan Shaw. Where is the boat based?

 

[Julian]

@Julian. possibly @Dan Shaw would get a better response if this thread were moved to the Sugar & Sands forum.

Moved to Sugar Sands Forum...

 

[Bilmon]

Not real familiar with the 175 but you have two fuel pumps . The electric one is activated when the starter is engaged to prime the mechanical pump that operates off of crankcase pressure. The electric lift pump has a fuse , I'd check that as well as the fuel lines as someone above suggested .Something has to be stopping fuel flow, the switch box has no bearing on the fuel system that I'm aware of. Look here for a trouble shooting chart for your motor's fuel system http://www.boatinfo.no/lib/mercury/manuals/175xr_sportjet.html#/102

 

[Gym]

Your electric pump could also be working but not delivering enough pressure. Could be a partially blocked screen or warn pump. Can you get the pressure specs and check your pump pressure.