Moved fuel tank to the front and fuel filter is not full when running

Moved my fuel tank to the bow. Used a 3/8 ID copper fuel line to back of boat. Flex hose and primer bulb from tank to copper. Back of boat copper stub out to flex hose. Flex hose to clear water seperating filter (clear plastic bowl with silk screen filter housing). Flex hose from filter to outboard. When I run the engine, starting with a full fuel filter, after sev mins the fuel filter level drops to about 1/3. Now inside the silk screen fuel appears to be to the top. I can see the fuel entering inside the filter while running. I tried it at the lake and the fuel level never seemed to get any lower even at full rpm. I am 100% sure no leaks air intrusion. Should I install an electric pump and remove the OEM pump? Or just run as is? I know what will happen when it leans out.

if you pump the primer bulb does the level go up?if i understand this right the feed before any filtering is done goes to the inside of the silk screen which you say is full?and then after the fuel is filtered through the silk screen the the level is down?if this is correct then the problem is not getting fuel from the tank to the filter..as i read it the problem is getting the fuel thru the silk screen....moving the tank should have made no difference as the problem is in the filter...maybe the silk screen is too dense...maybe a different micro screen will fix it...did you just add this filter?if not did you observe the levels before moving the tank?

''A rule of thumb for sizing filters for gasoline engines is 10 percent of maximum horsepower equals gallons per hour (gph).''so you need a filter for a 100hp outboard that can handle a flow of 10 gallons per hour....thats minimum in my book....i would double it to be safe....i am not familiar with silk screen filters... a standard spin on water separator is 10 microns but they can be as low as 2 and as high as 30.....

lets review why we use a water separator....all we really want is to catch the water and with the ethanol gas thats gone to hell we will catch the white and yellow chunks of crap....there is an additional filter on the engine itself and that is where we have the lower micron filter...

The filter is a OEM Johnson filter it is vertical. Not sure but I believe it was normally installed between the fuel pump and carb. I installed the filter and copper at the same time. Copper is soft M for plumbing. I sweat on a female threaded adapter and threaded a bar to the flex. I tried the primer between the filter and the engine. There was not enough suction using the primer bulb in that location (behind filter) to start prime when empty. My observation is that the OEM fuel pump does not have enough draw to maintain full prime on the aprox 16' copper + 8' flex and filter. The only drawback I can see to an electric pump is that it would continue to pump if engine died.

Every filter i have used in 50+ years of boating has been installed between the primer bulb and the motor including ones installed by authorized dealers..a continuously running electric fuel pump is too dangerous in my opinion.....i went from a built in fuel tank to 2 six gallon tanks with at least 14 feet of 3.8 inch hose with a water separator with no problem on a 60hp merc....there are no splices in the hose...before i went with an electric fuel pump i would do the following..1.check the vent on the tank...check the anti siphon valve if you have one...check and replace the small filter on the engine....get rid of the copper lines and run the new marine hose...change water separator to one recommended by a dealer...

Since no one has asked, I will....Does the motor run ok? If you look at inline filters on cars, etc, they are never full. I have a 318 car engine in one of my pieces of equipment, and it has a clear fuel filter near the carb, after the pump. It runs 1/2 to 3/4 full. I have a bow tank on my 16' with a 115 on it. It uses copper lines from the tank to the stern, then a rubber line with the primer bulb to the engine. No extra filters, that's the job of the one on the engine. Never had a problem with it.

The engine I just rebuilt. In the break in stage now. Runs very good. The only filter on the 79 johnson 55hp is the stainless screen in the fuel pump. Not very effective IMO. My main reason for adding the filter was to remove the minute water droplets that seem to accumulate in the bottom of the fuel. I see what your saying about the filter not being full when running. Probably me just being overcautious.

The strange part of the filter not being full to me is that fuel somehow stays in the inside of the mesh to the top of the filter but outside the mesh the fuel level is aprox 1/3 full. The mesh looks like a super fine silk screen.

It just never changes.-------------Over 40 years ago I explained to folks , that is the way the filters and sight glass worked.---This was on the OMC motors of the 1960's.-------Primed and the glass bowl was full, when motor ran there was just a trickle of fuel visible in the glass bowl. Motors ran just fine.------Outboards are such wonderful " different " machines.

Does the fuel run into the fine mesh first, then to the outside of the bowl, or the other way around? On the clear in-line filters I use on my eqipment, the gas (or diesel) runs into the outside, then thru the filter, and then to the carb or pump. That way you can see if the filter is getting dirty, and needs replacing or cleaning. I run a variety of outboards, and haven't installed an extra filter on any of them. As to the small water droplets, a bit of Seafoam in each tank works for me. I've got a 72 50 hp that has never missed a beat, 3 115's, a 150, and some 58's of different hp's that run just fine without any extra filters or water seperators.

Whatever you do, don't add an electric pump!! If a line splits, or a hose cracks, or if a carb float sticks open, you are gonna be sitting in a bomb!!!

Fuel comes in the filter bowl, goes through the outside of the mesh, exits through the center of the mesh. Clear bowl unscrews to drain the water/sediment and clean the mesh. Before I rebuilt my engine I cleaned my carbs several different times and observed the water droplets in the bottom of the carb bowls. Fuel mix was fresh.
Good info on the fuel filter operation. You learn something new everyday.