Fuel Delivery advice needed

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newcomlr

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Jul 5, 2012
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Posted in Pontoons earlier...should have posted here.

I have a Potoon with a 22' gallon tank and a 60HP two stroke 2003 Mercury Big Foot. After some issues with bad fuel and/or water in fuel last year, I added a water/fuel separator in the off season. I had one of those see thru in-line fuel filters already, and I just left it on after adding the separator. Primer bulb is new from late last season and all fuel hose (3/8") is brand new from marine dealer. Checked tightness of all fittings.

I suspect that I'm not getting good flow now and may be running lean. The boat starts fine, but definitely down on power. Additionally, when priming the bulb, it doesn't seem possible to get the primer bulb hard and I'm not seeing the full flow in the see-thru inline filter as I saw last year (without the separator installed). The illustration below depicts the current set-up.

I may go ahead and remove the see thru filter to see if that helps, but I like having it there. Is it common to affect fuel flow with the spin on type separators? The way I mounted the separator, I ended up using inlet and outlets on the same side of the housing....shouldn't make a difference, but wondering if using inlet/out on opposite sides would help.

Advice? Suggestions?

Fuel delivery layout.JPG
 
L

Laddies

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Re: Fuel Delivery advice needed

It doesn't matter, pull the high speed jets an clean them or clean the carbs
 
N

newcomlr

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Re: Fuel Delivery advice needed

Cleaned the carbs and jets before winterizing. The issue is fuel flow to the motor. Keep in mind, with the see thru inline filter, I can see the amount of fuel flowing...and it's not as much as before the install of the separator.

It's been suggested that I move the primer bulb to between the tank and the separator. I may go ahead and try that. It almost feels like there is air infiltrating through one of the connections.
 
Blindduck

Blindduck

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N

newcomlr

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Re: Fuel Delivery advice needed

I'll have to check the bulb...it wasn't a cheap walmart type, but I don't think it was Mercury or Quicksilver either. It looks like the marine shop I bought it at carries Moeller for these types of items.

Laddies....are you asking about the anti-siphon valve in the primer bulb?

My puzzlement is the bulb primed fine last year when I put it on, and since the only change to the set-up was adding the water separator, and updating hose, I'm guessing there is air intrusion at one of the connections or plugs for the separator
 
Last edited:
N

newcomlr

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Re: Fuel Delivery advice needed

Laddies said:
The anti syphon valve is in the fitting closest to the tank and at time they will get dirt or crud in them and not open fully or stick. anti syphon valve - Google Search
Click to expand...

Laddies, Thanks for the clarification. I'll check that. Frankly, I thought that was just a fitting. I had the tank out of boat all winter, and disassembled, but I don't recall looking inside that particular fitting or noticing it was a valve.
 
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newcomlr

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Re: Fuel Delivery advice needed

newcomlr said:
Laddies, Thanks for the clarification. I'll check that. Frankly, I thought that was just a fitting. I had the tank out of boat all winter, and disassembled, but I don't recall looking inside that particular fitting or noticing it was a valve.
Click to expand...

Update: Removed see thru inline filter and didn't seem to change anything. Went back through and removed, resealed and re-tightened all screw fittings and hose clamps. Primed bulb and it got firm almost immediately (separator canister was still full). Didn't have time for a test run, but hope to tomorrow.

Laddies: I removed the fittings at the tank and there is no anti-siphon valve. Fittings are all original so never was one. Scanning the interweb, it sounds like anti-siphon valves are required in situations where the fuel tank is below deck for safety reasons. Also sounds like they fail frequently and are cursed a lot. Doesn't sound like ADDING one to my pontoon fuel system will do anything to improve fuel flow, correct? But can provide a safety element? Thanks in advance!
 
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Laddies

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Re: Fuel Delivery advice needed

You don't need one for your use but many tanks are bought by the boat manufacture already have them installed, you don't want one as they are troublesome.
 
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newcomlr

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Re: Fuel Delivery advice needed

Still chasing this issue down. With the fuel/water separator installed, and the primer bulb between the separator and the motor, I still had problems getting the bulb firm and definitely couldn't keep it firm. Power was noticeably down as at WOT I was well off normal speed and RPMs. It seemed to me I was not getting enough fuel flow and/or pressure, and it appeared I was running lean.

I already re-checked all fittings and no improvement. I suspected an air leak at the fuel tank fitting, but I thought I would first try bypassing the separator. So with just the tank to bulb to engine, I primed bulb and got quick firm. Took toon out for a spin and power and RPMs were back up at WOT. But it was wanting to run a bit rough at low throttle, where with the separator on it ran smoother (but with power loss). I think the separator is a good idea and would like to use it. Anyone else run into this with a separator on a two stroke outboard?
Gas is fresh in last week and it has Starbright in it.

Is it typical for the separator....since it adds more space to fill with fuel...to affect the priming and fuel flow? Would it help to move the primer to be between the fuel tank and the separator?

Will recheck carbs for gunk and check in-line internal fuel filter, but I changed it late last year. The gremlin seems to be something in my set up between the motor and the tank. Open to any suggestions!
 
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newcomlr

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Re: Fuel Delivery advice needed

Replaced all other fitting at and in tank, and the quick disconnect at the motor. Moved the primer in front of the separator.

Took a while to get pressure by "push priming" but the motor seems to run better. I the fuel separator generally adds volume to the system so it's just different than just having a primer bulb between tank and motor.
 
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newcomlr

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Re: Fuel Delivery advice needed

Follow-up question. I still have trouble keeping fuel pressure/flow with the water separator. Don't have an issue when bypass the water separator, but the engine always seemed to idle a bit rough before installing the separator. But, with the water separator, I can't get the primer ball hard ever. And most curious are these two symptoms:

- Significant lower power/speed at WOT
- Can putter around the lake for hours with no issue, but if I dock or slow to idle speed, it wants to die out. Of course, a quick squeeze of the primer helps combat.

My instincts would tell me to clean the jets and check/replace fuel pump...but the issue isn't there except when the water separator is in the mix. I've double checked and even replaced and sealed all fittings, new hoses, etc. How would a mechanic diagnose? Would it help to hook a pressure gauge in the fuel lines and test at each connection?

I'm at a loss on this one...
 
ajgraz

ajgraz

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Re: Fuel Delivery advice needed

Do you see air bubbles in the fuel in your see-through filter?

From the description so far, sounds to me like the issue is somewhere in the separator. Exactly which separator are you using? Maybe the filter-to-flange seal isn't that great (nicked filter gasket, or a defect in the separator body's flange)? Or maybe the filter element got clogged with some tank gunk, have you tried a new spin-on filter element?

Or maybe you are right and one of the fittings in/out of the separator body is not sealing well, check the separator body for cracks around the fittings. Also, are you using any kind of sealant on those fittings? Something like:
Gasket Sealants : Permatex® Aviation Form-A-Gasket® No. 3 Sealant Liquid
 
N

newcomlr

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Re: Fuel Delivery advice needed

@ ajgraz:

Thanks for your input! I removed the in-line fuel filter earlier this season (after the original post) just so I could remove a variable. I could put it back on after the separator to see if their are bubbles. Good idea! D'oh. :der:

Separator is a Mallory spin-on canister type (10 micron) model 9-37811. I used sealed the threads on all the fittings on the separator...twice. Used permatex high temp thread sealant which says can be used for fuel components.

I'll look all over again, and remove and check the canister. What you are describing would explain it...something like a crack in the filter flange, etc. There shouldn't be any fuel tank gunk since I removed tank from boat in the off season and cleaned it and kept inside all winter.
 
Blindduck

Blindduck

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Re: Fuel Delivery advice needed

Is the seperator all that important? I run a 50hp 2 stroke 2009 merc (just about the same motor)and have no problems with water in the fuel. I try to run the motor at least on the ears every three weeks if I haven't had the boat out on the water to keep the fuel fresh. Also use the quick silver fuel treatment. I'm still thinking your fuel is running back into the tank due to either a leak or bad check valves in your primer. If you don't have fuel spilling all over the place it's not a leak.
You should do the test I described in one of the links. Fuel pressure gauge attached to the disconnected line to the pump. Pump the bulb. If the pressure drops it is not fixed and will not run right untill you can get the pressure to hold after primed. Good luck!
 
O

oldman570

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Re: Fuel Delivery advice needed

If the fuel pump is the standard manual pump then it could be that the added see thru filter along with total setup is causing the trouble. Manual pumps will only pull about a 3.5' lift at max. The primer bulb needs to be in the vertical position if after market and factory bulbs don't matter . The bulb should be between the tank and the fuel separator then straight to the motor fitting, then thru the pump and then the see thru filter from the factory. That motor was also made with a electric pump on the motor and both setups should be the same. The extra filter along with how far the pump is trying to lift will cause trouble even if there are no air leaks in any connections.
With a separator and the see thru filter on the motor, no other filter is needed. JMO
Oldman570
 
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newcomlr

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Re: Fuel Delivery advice needed

Ok. I am officially embarrassed, yet somewhat relieved.

Somewhere along the line when changing fuel hoses, fittings, etc., I must have put the primer in backward....or it's possible one of my dock neighbors is messing with me. Or if I did it, the primer is a cheap Kohler (sp?) and in my defense, the arrow is very hard to see. I could have sworn I bought it at the local boat dealer and thought it was at least a quicksilver or atwood! Interesting the thing ran at all!

Put it in right and in doing so noted the check valve doesn't work very well...which probably aided the motor running ok when the primer was in backward. New OE primer ordered.
 
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