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Hi, I've posted in the past and for most of the summer, tis engine was going great: I had rebuilt the carbs, put in new plugs and cleaned the fuel pump.
Now, just this week, it has started to die out at WOT, but recovers if I pump the fuel bulb. I bought a rebuild kit for the fuel pump and put that in today, but no help. The new diaphrams are tighter, so I know they'll help eventually, but for some reason the bulb won't stay hard.
I'll get a new fuel line from tank to motor soon and try that, but I just don't know where else I should look. I think somewhere there must be an air leak and the pump can't get suction.

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I think you're on the right track... I'd think it must be sucking air somewhere. Any other ideas?

Dan <--- winner of the dubious "top poster" award! Come on, MW.... get crackin'!

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Hi Jtaylor,

Fuel delivery to an outboard has always been its weakest link.... You have done the right things. Since you have replaced the fuel pump, it may be the line. I have had issues with fuel lines so that may do trick when your replace it. You do not mention the type of boat and tank. Could be the tube and the connection at the tank as well....:|
good luck

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I'm having a similar issue and the fuel line is my next replacement item. Have you noticed more smoke than usual from the VRO lately? If so, this could indicate an air leak before the fuel pump, either a connector or line, and could help nail down the problem.

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It's a 17' Montauk 1982, the Johnson is a 1999. The VRO is capped off, I just mix 50/1. I have (2) 6 gallon tanks.
Every thing was working fine until recently. I'm going to check the tank to engine line first, then I'll just replace the lines to the carbs and that feed the pump. Thanks for the replies, I just wanted to be sure that all this might be a different issue, but it has to be an air leak somewhere.
The first 5 minutes or so of running are fine, but then it struggles to pump gas. Which line is the vacuum line to the fuel pump?

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Check the fuel line, sounds like possibly a check valve has hung up in the bulb, or air leak, did anyone touch the fuel lines ? Is the arrow on the fuel line leaving the tank, and pointing towards the engine ? I hooked up my fuel line in a hurry once only to realize I put it on backwards (later). I limped back into port. A repair shop happily fixed the problem, and handed me a bill for two rebuilt carbs on a 3 year old Evinrude 48 SPL. :o
mw

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Have you checked the vent on the tank?If it's closed or blocked......

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The vents are open and seem fine, I've tried both tanks. This problem just happened out of nowhere, but I think it may be a leak or hole in the fuel line to the engine. The day it happened I took a few people out fishing and someone may have stepped on or knelt on the line.
Could it be the electrical part on the VRO? I have replaced both diaphrams, the o-ring, the rubber washer and the steel shaft. There is a magnetic shaft that fits into the solenoid, could that be it?
At low speed, the gas supply is enough, but it will stall out when I push the throttle. Yesterday I went about 30 miles at full speed, by pumping the bulb by hand.
I'm off to get a new OMC line and some new fule lines to redo it all. This motor sat 7 years with gas in it, so it wouldn't be a bad idea to do the lines.

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My 2002 Nissan 25hp 4 stroke (less than 40 hours) is in the shop for the same reasons. Was running great on numerous occasions then all of a sudden it would not get past 5 minutes without the rpms dropping and running rough, and I'd limp home

I also check the fuel, vent cap on the tank, got a new fuel line to the engine and the same problem occured. First mechanic I took it to could not recreate the problem on the stand but I still asked for him to clean the carbs. Picked up the boat all happy thinking that was the trick, put it in, and same problem.

Now, it's back a the dealer who sold the motor in the first place. I should know this week of their diagnosis. I'll let you know what I find out.....

If only the engine were as uncomplicated as my 1972 13' Sport!

Denny

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Yes, please post when you find out what was wrong. I just picked up a new OMC fuel line/bulb. I'll take it out tomorrow and try to figure it out.

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Are you getting any warning/low fuel alarms when it starts to bog from lack of fuel?

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no warnings. If it's still the VRO pump, what part of it isn't working right? I put in all new diaphrams. I'll try out the new fuel line tomorrow and see if that's it.

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The springs get weak on the fuel lines where they hook up to the motor and tank, this prevents the pin's from behing pushed all the way open.
mw

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I bought a new OMC line from tank to motor, it made no difference, I had the fuel pump pulled off again today. The vacuum lineseems to have proper suction, I don't know where else to look. It's definitely a fuel delivery issue because if I pump by hand, I can run at full throttle.
I'll start tomorrow by replacing all the lines into and from the fuel pump. I'll most likely open the pump and make sure there's no clog or problem. I did replace the 2 diaphragms but that didn't help. What role does the smal electrical part of the fuel pump play? I think that's the oil side, maybe it controls the amount of oil? I just mix 50/1 anyways.

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Hmmmm, I'm thinking "Pick up tube" cracked in tank, or screen clogged, do these check out o.k. ?
mw

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Give this Article a read, it'll explain the VRO/Fuel pump questions you had.

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Just had another thought... What about the gasket inside the factory fuel filter just inside the lower cowl and before the VRO pump, have you checked that for integrity/air leaks?

If you're not getting any alarms when that happens, chances are they disconnected the warning switch when they took the VRO out of your system as it seems clear you're running out of fuel when it bogs.

On my engine, I can't seem to ever get a hard primer bulb and always get the low fuel alarm each time I start the engine. So while looking at a parts diagram on the BRP site tonight, just realized that the previous owner has put that little fuel filter in upside down! So I'm going to check that out tomorrow and see if I can cure my alarm/bulb issue. It's worth you taking a look at too. I'll let you know if I come up with anything else that may be relevant to your problem.

Dave

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You should NEVER, NEVER rebuild any VRO or fuel pump. It will never completely seal it self back up correctly and is very prone to quick failure again.

If you are running a VRO pump and have just capped the oiling side off there is an issue right there. You should never run a VRO pump with just the oil side capped as the pump will only work at a much reduced rate. It needs fluid on the other side of the diaphragm to help get a strong vacuum and pressure. It is just like having air in your brake lines. Air molecules are much less dense than water. If you are going to run premix and not run your VRO system you will need to replace your VRO pump with just a standard fuel pump. Though I have no Idea why so many people see the VRO as a failed system.

If and when you get the VRO / Fuel pump issue straightened out and you are still having the same issue you will need to start back at your carbs. I would start by replacing the jets with the next size down and see it that makes it better. If that helps but does not solve it completely go down another size. If the problem gets worse start going larger.

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Apparently, my engine is finally ready. The mechanic took it out and ran into the same problem (which actually relieved me!). He said he basically pulled the carbs and soaked them overnight.

I pick it up tomorrow and l will let you know how things worked out over the weekend. I'll also see if I can get him to explain in alittle more detail exactly what he did.

Denny

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I fear you won't get much detail from him as he did almost nothing for those carbs...soaking them overnite will not return them to operating condition...they need to be fully disembled...completely soaked to remove varnish build up and new parts( needles, orings, gaskets,floats) installed...and THEN perfectly tuned to operate right.....it's a tricky process not undertaken lightly...
I hope he didn't charge you too much....:|

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Whatever he did worked fine. Everything is running great now. I'll keep my fingers crossed.

Charged me $110

Denny