40 HP VRO power issues

If you're reading this for a second time I apologize. I posted a similar post yesterday but I don't know where it went.

I have a 40 HP Evinrude VRO (1990) that had the oil side bypassed when I purchased it. I use a 50:1 mix. It never really ran well from day one was always tough to start. The biggest problem was that I could never keep it running in low speed.

I rebuilt the carbs, replaced the spark plugs and in line fuel filter and gas. I set the throttle linkage and carbs up according to the manual. I adjusted the low speed needle valves as best I could by ear since I have no tach. I didn't mess with the timing - sine I have no experience. The results were very good at first. It started every time right away and I was able to run it at low rpms and high rpms without issues but after a few days on the water, it would bog down when trying to accelerate from low speed. It would then speed up and slow down repeatedly until I backed off the throttle. If I periodically pumped the fuel line bulb at full throttle it would run great. I still have no trouble at slow speed or starting it.


Since then I've put ty wraps on all fuel lines and the VRO vacuum line. I also cleaned the fuel suction line filter/screen. No changes.

I've read a number of posts and have more questions now than when I started. I really want to open up the VRO pump to see if there's an issue internally but the manual said it can't be rebuilt but I read in a post that rebuild kits are available. (The manual covers a variety of Envinrude motors and years as well as mine) ???
I also read on another post when an individual was having issues similar to mine and it was recommend that he back off the low speed needle valves in 1/8 turn increments. I'm going to try this but I'm curious why this would help a high speed issue.
I also read where someone replaced his VRO pump with an electric pump. Is this an alternative if I can't rebuild the pump? My pump has an electric choke which appears to be a part of the VRO pump.

Any help would be appreciated.

The electrics on the VRO pump are a warning system.------The seperate electric primer solenoid is nothing but a valve that opens when key is pushed in during cranking for initial starting of the motor.----There is a pump available that mounts directly to the side of the top cylinder on the port side.----Look that pump up on say a 48 HP motor like yours.

I've looked up a 48 hp motor pump replacment - I found an early (18-7352 - FUEL PUMP, 438556) and a late model production. Does it matter which one? The early one has a casting fitting - not sure waht that is or if it matters. I take it that the pump is driven from the crankcase and that I will have to remove the pulse limiter and replace it with a nipple (just a guess based on what I read on other threads).

Also can adjusting the low speed needle valves be a solution?
Can I take apart the VRO and inspect it. Hoping for a quick fix cause of the holiday and house full of comapny.

Thanks again!

One pump ( 48 HP ) bolts directly to the block with a gasket.---You have to remove the plug for the pulse port.------------You block the hole that was used for the pulse for the VRO !

Thank you for you help. This morning I verified it was the pump by removing the main discharge line and cranking the motor. Little to no fuel was discharging. I took the pump apart and found the diaphragm was torn. I temporarily replaced it with a VRO pump from a 60 HP Evinrude I have. Works great but I plan on picking up a non VRO pump