I’m still stuck on what the problem is . Should I check compression ? Or could it be issue in carb ?
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I'm not gonna repeat anything about is this or that marine rated, there's enough others that that do that.
1st get rid of that second fuel filter on the inlet of the Edelbrock micro pump. You don't need it you already have the fuel water separator.. extra fuel filter isn't helping.
The fittings on the mercruiser fuel water separator filter is 3/8 hose barb.. the Edelbrock micro filter unfortunately has 5/16 hose barb. You need to get a 1/8npt to 3/8 hose barb fitting for the inlet side and for the outlet you need a 5/16 hose barb to 3/8 hose barb fitting to adapt from 5/16 to 3/8 hose to the carb.
2nd I just installed a "marine" Carter fuel pump and it's garbage. Only 3 psi at idle and at 2500 RPMs struggles.
I installed the same pump as you and now I get 4 PSI at idle and 5-5.5 psi at 2500 RPMs. Make sure you do wire in a relay and oil pressure safety switch..if you just wire the fuel pump to ignition 12v then your fuel pump will just run all the time even with the engine off and we don't have fuel return to tank so that's bad for the carb and can flood the system.
3rd make sure your fuel pump isnt more than 24 inches above the top of your fuel tank..it can struggle to pull fuel through 2 filters and against gravity if it's too high.
4. I think it's your carb... I had the same problem in my old boat where under load it would break up or die and I had to ease through the throttle to get it on plane .. sometimes that didn't help. I ended up replacing the carb and problem was solved.
The only difference between the "Marine" Carter fuel pump and the Edelbrock micro pump besides the fact that the Edelbrock one just works...is that the Carter one had rubber boots that insulated the electric connection to the posts...
The Edelbrock one has the wires coming through the body and it's a sealed unit so I have no issues running this non marine fuel pump. There is no spark risk with this pump since I made sure to use marine heat shrink male/female bullet style connectors with sleeves and as long as you run it with a relay and oil safety switch.
For starter and alternators that is something I do recommend making sure you get marine grade
