Looking for advice before I send it to the shop.
I have a 1995 Mariner 175 EFI that's having a issue ,after running on plane for about 100 yards it would fall flat on its face .
The fuel electric fuel pump was changed 3 1/2 years ago ECM was reprogram about same time.
I changed fuel filter, cleaned the screen in front of fuel pump, checked voltage going to fuel pump the reading was at 32psi volt 7.76 .then pressure drops to 30 psi voltage reads 7.83
26 psi reads 7.92 , 22psi reads same 7.92 volts .
I just wanted to see if there is anything I need to check before I dump 500 in another fuel pump any ideas????

none of that sounds right at all.. that pump should run at 2 speeds.. a little slower @ 2000 and lower.. above that runs at max.. motor will not act right below 34 lbs.. tha ecu controls speed with tha ground going to tha pump.. easiest way to check pump and/or ecu driver circuit is to by-pass the ecu and run tha pump direct.. do this by disconnecting tha two wires on tha pump now and tape them up.. connect a ground to tha neg. terminal then find tha "purple" coming from tha main harness.. should be on a terminal right above tha switch boxes.. use it as a positive to tha pump.. this will run tha pump anytime tha key is on.. if this gives right pressure at ANY speed tha pump is good..ecu not so much..

know several folks that have ran theirs like this for years but its best to add a relay ta run tha pump if ya choose NOT to replace tha ecu.....jmo

JAN. did ya find tha little cone shaped filter in tha "U" shaped hose?

Have you checked the hidden fuel filter in the hose that runs between the electric fuel pump and the VST like TLW said. I would clean the fuel pressure regulator screen and the screen after the electric fuel pump to. Any of these will cause erratic fuel pressure readings.

I didn't change the cone shape filter ,could the diaphragms in the black square box that some people call the fuel pump need be changed.This 2" square box that has 3 fuel lines going to (fuel pump)(non electric) one had the 4 screws cam loose i just add lock tight and re-tighten.

It can not hurt to install new diaphragms.

this....


get tha complete kit for it..when they "come loose" it will ruin tha little gasket between it and tha block..

it is a mechanical fuel pump that keeps tha vst full.. tha line tha connects to tha "middle of tha square" is a vacuum line....

I rebuilt the mechanical fuel pump ,replaced the filters.cleaned the screens,still only 28 psi on electrical pump.
i bypassed the ecu to the pump as TLW was talking about it boost the psi to 38 psi so it must be a ecu issue.
Would it hurt anything to keep buy passing the ECU to the pump.
We had this ECU rebuilt while back it was around 2 grand really not looking forward to that again.
TWL talked about putting in a relay .what size ?

like said, some have run tha pump with tha "purple wire" for a very long time without problems but I really rather use a relay.. here's two.. I like tha Painless best...

http://www.summitracing.com/parts/sum-890023

http://www.summitracing.com/parts/prf-50102

justa note.. there a VERY FEW that can actually fix a ecu no mater what they say.. even with tha so-called very best its pot luck with 'em... better odds with ebay.. at least ya can get your money back if its DOA!

Thanks TLW
Im finding that out about getting your ECU repaired .The hard way .Thanks for all your help.