Question for Either TheFermanator or Spareparts or anyone else that might know.

[Destroyer]

Originally Posted by THEFERMANATOR

Electric pumps are very doable, but why? Old school outboards were meant to be able to run without any electrical power needed short of the starter(and some have even tried to rope start the big outboards as well in an emergency). As far as running the fuel pump off the crank, that would require ALOT of added expense to build VS using a pulse type pump. Pulse pumps work fine, and are cheap and simple. Almost all lawn mowers with a pump still use a basic pulse pump, and you rarely have problems out of them. The OMC loopers though required the more complicated style pump like the VRO pumps to pump enough fuel. The OMC loopers work off of a very efficient crankcase flow pattern, and after about 3500 RPM's the crankcase stays almost pressurized constantly. this is why OMC's used teh more complicated VRO differential pump whereas other outboads stuck with a basic pulse pump. When they work they work, but unfortunately the VRO style pump does have more failures than other diaphram pulse pumps do to there design. They do though pump alot more fuel with not much crankcase differential pressure.

Well, my thinking was that if one could no longer obtain the proper part from the manufacturer, and they didn't want to junk the engine, then maybe an electric pump might just save the day.
As to the rest of the post, that's exactly the kind of info I was looking for Ferm... I may not like the answer, but at least I can understand some of the reasoning now. Many, many thanks.

[spareparts]

Ferm explained it pretty good. BTW some 2 stroke outboards use electric pumps, the OMC V8s had them, an electric primer pump was offered on the OMC seadrives, and the Yamaha VX76 has a stand alone electric pump that dumps extra fuel in at higher rpms thru an ecu controlled solenoid in each carb

[aussie]

look with boats cars anything its all down to dollars they look for the cheapest way and best way to make things ill be running electric water pump and fuel pump 2 reasons cheap to replace and added hp on some things

[THEFERMANATOR]

When you have an engine with a good differential pressure in the crankcase, the pulse type vacuum pumps work great. Also they draw virtually no HP from the engine since the moving parts are driven via crankcase pulses instead of a mechanical means. Also factor in that magneto type charging systems put out virtually nothing at idle, so the fuel pump running at idle will pull the battery down a good bit at idle. i know my old 140 would put out less than an amp at idle, but push 9 amps or so at 5K. The thinking was if you didn't need a better mousetrap, why re-invent the wheel.