Fuel pump issue

Hi enyone had similar issue?
Mercruiser 4.3 lx 4 barels carbs
Totally overhauled (all components new)
One month ago i had an issue wile i was running, boat stopped like if i had no petrol. I re start the boat and everithing was ok i run the boat for all month on small ride with no issue.
Tonight i run the boat for longher time (2hours) and issue started again after one hours more or less.
Boat was running well 21 kn 35/38 lt/h
Suddently it was dieing like i had no petrol ( i had ) and then i put down the gas i check my garmin gs10 petrol flow meter and i started to run the boat. Not enought petrol was passing through the flow meeter (max flow sow on display 24 lt\h
I stop the engine and wait 20 min then i started again
Now flow was ok 55 wile i was starting out of the water and then 38 lt\h
After 10 minutes it started again
I stoped the boat and re start again ok for other 10 min then again on display i noted
10 min ok petrol stable at 38 lt per hours
Then suddently petrol indicator were floating 40-30-20-40-20-45-20-15 stop
I have the video vut i can not upload, i dont know why ( i upload on youtube but i can not copy the link)
Anyway every time i was restartimg it was ok for 10 minutes then everiting again, at the beghining just number changing but still running ( 38 lh/h then 25 then 45 lt/h then 19 again then boat started to die for no petrol) and again again again
I run also with tank tap open just to avoid breather issue but same resoult.

pump is new , not original one but not cheep one either (180€) and it run only for 20 hours in total

It seems like it is pump issue but strange behaviour i think

What do u think?

Anyone had similar issue? It seems that when its get hot (it is attached to motor body) it start this issue

If someone help in post the video i will upload it
Tks

Tks

Trash blocking the anti-siphon valve on the tank outlet?

kd4pbs said:

Trash blocking the anti-siphon valve on the tank outlet?

Click to expand...

You meen the breather? The one that compensate the oxigen inside the tank?
I try to run with tank plugh slightly open to let ait goes inside to avoid this but no change .
I only can think the pump or fetrol sucking tube inside tank that is succking some debrids, but i remove all old petroll and use new petrol at the beghining of the summer. i will try to see if i can remove and check it tomorrow as well

Where the fuel line is attached to the tank there is a fitting with with a check ball this is the anti siphon valve.
Also a good time to unscrew the main fitting with the suction tube. Inside the tube there is usually a very fine mesh filter which needs to be removed and blown out, it is supposed to protect the anti siphon valve.

kenny nunez said:

Where the fuel line is attached to the tank there is a fitting with with a check ball this is the anti siphon valve.
Also a good time to unscrew the main fitting with the suction tube. Inside the tube there is usually a very fine mesh filter which needs to be removed and blown out, it is supposed to protect the anti siphon valve.

Click to expand...

Today i will try to check this check valves and if i can remove the suction tube to check if there is a filter. U think is not pump issue?
Pump is getting hot wile is running but it is attached to the motor , and motor is 70 deg so it get most probabilly same twmp very soon

kenny nunez said:

Where the fuel line is attached to the tank there is a fitting with with a check ball this is the anti siphon valve.
Also a good time to unscrew the main fitting with the suction tube. Inside the tube there is usually a very fine mesh filter which needs to be removed and blown out, it is supposed to protect the anti siphon valve.

Click to expand...

I checked
Check valves i think is not installed.
I had this boat since 2010 and never made madify on this so if it was removed it was from before.
Filter in the suction pipe (small metalic one) is clean
I blow in the pipe and it was free

When was the last you changed the fuel filter(s)?

To eliminate the fuel storage system as the problem, connect a hose downstream of the fuel tank and drop the hose in a can of petrol. See if the problem goes away

Filter in suction pipe
And petrol in main filter seems clean

I found a lot of dirty in whater separator filter, but not sure how clean was the tank that garage gave me

dingbat said:

When was the last you changed the fuel filter(s)?

To eliminate the fuel storage system as the problem, connect a hose downstream of the fuel tank and drop the hose in a can of petrol. See if the problem goes away

Click to expand...

filter had 20 hours
Now i bought 2 filter and i replace them just to avoid doubt

ste80 said:

I checked
Check valves i think is not installed.
I had this boat since 2010 and never made madify on this so if it was removed it was from before.
Filter in the suction pipe (small metalic one) is clean
I blow in the pipe and it was free

Click to expand...

Ayuh,..... It's usually part of the hose barb,.....

ste80 said:

Filter in suction pipe
And petrol in main filter seems clean

I found a lot of dirty in whater separator filter, but not sure how clean was the tank that garage gave me
filter had 20 hours
Now i bought 2 filter and i replace them just to avoid doubt

Click to expand...

The water separator filter is typically the problem filter. Should be changed at least annually.

Another place to check is the small filter in the carburetor inlet.

dingbat said:

The water separator filter is typically the problem filter. Should be changed at least annually.

Click to expand...

It was new just 20 hours
Now i replace again both.
I have the doubt if low pressure pump can support 2 filter

kenny nunez said:

Another place to check is the small filter in the carburetor inlet.

Click to expand...

Carburator was overhouled totally like all the motor 20 hours ago i can take in part again in case

I can not post picture they said error dont know why

Update:
I replace the filter ( original one and whater separator one)
All original
Replaced the pump (with identical model, not original but not chinese ) but nothing same behaviour after more or les 40 minutes running it stop.

When motor stop the pump.is very hot
If i colled it down with water motor start again immediately so i think 99% is the temperature in pump area

I removed fuel separator garmin gsf10 and connect directelly to the tank but same nothing change

In lx motor the pump is attached to the cylinders block and on the back of cooling pipe ( big one from thermostat to circulation pump) so after certain time if the motor has 70/75 deg also the pump has same temp

I just wander about pump quality

Motor as said is all new only modify i made was to apply the front plates coming from efi motor in order to use the efi alternator that i had new from my previous motor . The plate allow to install the alternator on left side on the top and use one belt only for alternator steering and whater pump.
I don't know if this plate can make the area hoter but i dont think so because as said pump is really cloose to cooling pimpe ( the hot one) and attached to motor body so this is what make the pump very hot

I'm thinking to move pump from motor side to boat side and connect with flexible hose at this point

Oh… this is an electric pump! I thought this was the regular mechanical pump such as what would be on a carburetor engine. Yeah, electric pumps don’t like getting hot.

kd4pbs said:

Oh… this is an electric pump! I thought this was the regular mechanical pump such as what would be on a carburetor engine. Yeah, electric pumps don’t like getting hot.

Click to expand...

I agree, but pump is in original position
And this lx was born with electic fuel on it so i can not understand .
Maybe original pump can work at higher temp then mine i don't know
But all other lx has electric pump on it

It is a time & use related problem.......... Your replacement might be a unit made same date as yours. Bad quality units. Is your engine running a NEWER AND HOTTER thermostat ? Check pump temp with a a laser dot thermometer.

Is this fuel injected? I've never seen a fuel injected marine engine fuel pump that did not circulate raw water through it to cool it.

Some EFI pumps bleed oof a percentage of the HP fuel to the gas tank. New fuel in is cool. Different ways can be used to return the hot fuel to the gas tank.