Starving for Fuel, not sure why?

[myintro2boats]

The Breakdown: Have 1994 Johnson 70hp Outboard on 17'Key West

Current Issue: Boat won't plane unless I manually prime gas bulb while 2nd person mans throttle & wheel. It will run fine for about 100yds then drops and sputters. If I prime it again..it returns to "Normal"

Background: 1. I have already made certain all jets/carbs working great (orig. bottom was clogged)
2. Replaced faulty temp switch which kept boat in "SlowMode" even when priming bulb.
3. Inline fuel filter on OB is clean & less than yr. old, it is at least 1/2 full of fuel
4. Replaced primer bulb on fuel & oil reservoir, both were orig (to rule out poss. bad valve. no change).
5. Fuel Sending unit was replaced last fall and ran well afterwards.
(was replaced because fuel didn't register on gauge)
6. Primer Solenoid tested and working fine (was replaced last yr. due to leaking fuel.also ran well after)
7. Removed fuel hose @ connection to OB, primed to remove air & rule out blockage.
8. Fuel in tank is fresh and greater than 3/4
9. Spark pluggs also new, No excess heat to cylinder heads..well over 4 sec. rule (peehole working)

Help Needed: Any suggestions why fuel is not making it from tank to bulb? Would it be the fuel pump or air leak? If air leak where should I start looking?

 

[Daviet]

Re: Starving for Fuel, not sure why?

Usually if you can make the engine run properly by constantly squeezing the primer bulb, the fuel pump is defective. Try checking the flow and pressure on your pump.

 

[N1NE1]

Re: Starving for Fuel, not sure why?

Try removing anti siphon valve on top of fuel tank and replace with a barbed fitting.

 

[jerseyboy1983]

Re: Starving for Fuel, not sure why?

I had the same issue on my Evinrude and it was the VRO (fuel) pump. Don't waste any more time or money on anything else. Just give in and get a new pump. I'm wishing I did. But the time I did all the small and cheaper things everyone told me to try, months went by with no fix and it was the pump after all. And after I added up the cost of all the cheap things it would of been the same cost to just buy the pump. And I would of been on the water sooner. Being you have a 70 hp it should be a lot cheaper than mine. I paid 400 for mine.

 

[emoney]

Re: Starving for Fuel, not sure why?

Those VRO pumps do go bad from time to time. You can also check the diaphragm on the fuel pump pretty easily by removing the cover. It's it's cracked or torn, that could be your issue. TO confirm it is or isn't the fuel pickup screen clogged, you can run it on a remote, portable tank. If the problem repeats itself, then you know it's not that.

It's usually a process of elimination when it comes to fuel issues....well, any issue I suppose. Good luck and keep us posted.

 

[myintro2boats]

Re: Starving for Fuel, not sure why?

Thank you all for the great insights, I will try them and keep you posted.