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Fuel pump or air leak in gas line

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bwaybrown

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"Posted here couple days ago.

"Posted here couple days ago. 92 johnson 70hp. I checked carbs, seafoamed and the outboard is running much more smoothly. I still have a stutter under acceleration and at higher speeds. the bulb will not stay hard, my external fuel filter drifts down to about two thirds full and then I get the stutter. I can repump the bulb to stiff and away we go which makes me thik its a air leak or its a fuel pump not being able to pull enough fuel but why the soft bulb? How do I test for an air leak aside from looking for any clear problems. I can't see anything. I dont get bubbles in the external filter. Is there any sure way to test for air leaks and also how do you test a fuel pumps output? Any ideas or help will be appreciated."
 
"If you have a VRO pump, there

"If you have a VRO pump, there is a hose connected to a (pulse limiter), which is mounted on the engine..

Could be clogged, preventing enough of the crankcase positive/negative pulses from driving the VRO pump.."
 
"usually when you pump the pri

"usually when you pump the primer bulb and the motor picks up your fuel pump is going out.

your primer bulb wont stay as hard as it pumps up during your starts. all its for is to fill your carb bowls full of gas, the primer bulb is a manual fuel pump....but if it doesnt pump up hard then the needles in your carbs arent sealing or a fuel leak is present somewhere else."
 
"I mix my fuel and oil so I do

"I mix my fuel and oil so I don't think its a VRO. I am not positive, how would I check?
Is there a test to see if pump is going out? Can I test vacuum at the fuel filter or something like that. Spark good, compression all 120. Lastly, it seems simplest to purchase a new fuel pump instead of trying to rebuild. Not to familiar with outboards-hard to replace fuel pump if I have manual? Thanks all."
 
"if u r mixing your fuel,u r e

"if u r mixing your fuel,u r essentially,'OFF' the VRO but may be using the fuel side...a VRO is a blk plastic pump.someone may have chg your eng back to the old style pump too.there are tests,u can do,both pressure and vacuum...I suggest,u get a factory service manual ,it would be of enormous help,if u choose to service it yourself."
 
"So it is a VRO pump using the

"So it is a VRO pump using the fuel side only. I looked for the replacement 5007420 kit ay, f pump +lmtr and it was 400.Is there a non VRO pump that is less expensive? I found a service manual on ebay for 25 dollars which I bought. By the way, pretty sure it is fuel pump at this point. Put a new bulb and fuel line directly from tank to outboard bypassing external filter and the stutter started happening almost immediately."
 
"yes you can ues another pump

"yes you can ues another pump ,personally i do not
know witch yet but there have been other conversations about this topic before.
I remember this because my engine is setup like yours now using fuel side of vro,just waiting for it to go .i will do the same.
my bets guess is any pump that pre dates the vro sys with matching horse power will work"
 
"the fuel pump only,is about 3

"the fuel pump only,is about 340.00
now,u should be able to use the old 50.00 pump,lets say for an 83 70..look that up...may need to do a lil plumbing."
 
The first time this ever happe

The first time this ever happened I had forgot to open vent. I have since used the boat at least five times and opened the vent every time. I still get the same result. Maybe I damaged the pump when I did it the first time? I don't know but it happens all the time now.
 
"adam,

if it was me i would

"adam,

if it was me i would go jwb's direction and get a new fuel only pump.

have you found any leaks at all?

does the primer pump up good and hard?"
 
"Primer pumps hard. Boat runs

"Primer pumps hard. Boat runs fine if I pump it all the time. Makes me think its a pump but at 350 for the gas only I better be right. I never found air leak. I have a glass filter at the engine and an extermal filter/seperator in line. They both never stay completely full but a lot fuller when I manually pump. I have to jsut buy the pump and see if that is the problem. Sucks to guess on 350 item but most everyone here thinks its a pump, so do I so I am going to use the ufel only pump and swap it out. Thanks everyone for the advice."
 
before you buy the high dollar

before you buy the high dollar one i would run a search.......ive seen ways to modify the older $50 pumps like jwb was talking about but cant remember exactly where ill look though.
 
"that it the best way to go,do

"that it the best way to go,dont buy a new vro system if you are not going to use it.
good link DR. i saved it for later"
 
"Thanks guys, the link is good

"Thanks guys, the link is good information. I really appreciate all the input. I will update once I get all the stuff in."
 
"OK, thinking outside the box

"OK, thinking outside the box here: if this engine has 12 volt output, couldn't a small solid-state electric pump of the type made by Facet & others be made to work? you'd still have to prime carb with bulb but once motor started, seems like this would work. you might need pressure regulator since carb needle valve assy was designed to work with very low pressure. ???"
 
"u would have to wire in a saf

"u would have to wire in a safety stop of some kind.....otherwise an eng fire could be deadly/disasterous if elect pump keeps feeding it.elect pumps are not rec for non FI outboards,safest to stay w/a factory type."
 
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