Water/fuel pump update plus holly red
 

So after the holly red fuel pump wouldn't self primed I rebuilt stock mechanic pump. I ran line from tank to mini filter, to mechanical, then to holly electric, then big filter then carb.. With motor running I get 6.5 mechanical and if I flip switch for electric I go to 12psi.. Didn't flood carb at idle.. I was wondering if electric pump sucking
Fuel same time from
Mechanical if this could cause problems to mechanical.. My plan is to test using only electric pump at 4000 plus rpm

Bump: I ran boat today, the boat wouldnt run wot on mechanical rebuild pump. cam needs welding, so back to my first ? Is the mechanical pump struggling bc i have it pushing the fuel through the holly pump????
Would that cause a loss of pressure?

It depends on the fuel pump i would think, if its centrifugal style pump there should be no problem pulling or pushing through it, on small aircraft it goes fuel strainer/filter electric boost pump (facet style electric pump) and then engine driven diaphram pump (same thing on a big block). Personally i think that you should try to set the boat up on the electric pump only if the mechanical is not putting out enough pressure. Also if you are not getting enough fuel you need to be careful about detonating the thing - check your sparkplugs if they are white i would not run the boat anymore until you get it sorted out. Look online for a sparkplug color chart with the correct fuel air mixture they should be sort of brown looking.

if the electric pump would not prime, that may be source of problem. i would check the fuel lines and pickup into tank for breaks or loose. try small gas tank hooked to fuel pump inlet, quick and simple test of fuel system. use electric or mech. don't use together, may cause more problems, or exagerate existing problem.

See if this might help if your wanting to run both pumps and the electric won't prime. One line in to filter from tank. Two lines out of filter. One to the mechanical IN and the other to the electric IN. Then the one coming OUT of the electric bypasses the mechanical pump and connects to a manifold which is connected to the OUT on the mechanical pump. From there the two flow together out a line to the carb. This way the mechanical should prime the electric.

Here's a link. Go to "Carb Fuel System" under the Installation Schematics. Be sure to scroll all the way to the bottom and read.
http://teaguecustommarine.com/index.php/tech

Still I don't understand why your electric don't self prime but then I don't know that much about them. Is this a mechanical on a sea water pump? If so why not just get a new sea pump? I would prefere leaving the electric out of the picture all together.

This looks like the manifold you would need however you could probably piece together something simular yourself for your style lines.
http://teaguecustommarine.com/index....nifolds-5.html