under fueling!! help please!!

[martynwilley]

have had my boat out a handful of times this year with the motor running faultlessly

i took it out for a test the night before scrutanering for local basic race and damaged the hydrolic steering system so failed and couldnt race. on that same day of scrutenering i 'fixed' the power steering and took it for a spin.

on ths outing i developed a fuel problem, was fine pulling out the harbour but as soon as i went to WOT the bowls would drain after 30secs or so and id have to shift into neutral and wait for pressure.

so since then i have had the boat out the water, i have replaced all fuel hoses from tank to carbs with new, all new stainless Jclips, new facet red top pump, fuel pressure regulator and even mounted a inline pressure guage under the carbs. the system primed and regulated to 6.5psi

took it out today for a run and the problem re-appeared after 3-4mins of WOT then back to 30secs then back into neutral to get it back.

sorry for the essay, any help appriciated guys

[baj666]

Originally Posted by martynwilley

have had my boat out a handful of times this year with the motor running faultlessly

i took it out for a test the night before scrutanering for local basic race and damaged the hydrolic steering system so failed and couldnt race. on that same day of scrutenering i 'fixed' the power steering and took it for a spin.

on ths outing i developed a fuel problem, was fine pulling out the harbour but as soon as i went to WOT the bowls would drain after 30secs or so and id have to shift into neutral and wait for pressure.

so since then i have had the boat out the water, i have replaced all fuel hoses from tank to carbs with new, all new stainless Jclips, new facet red top pump, fuel pressure regulator and even mounted a inline pressure guage under the carbs. the system primed and regulated to 6.5psi

took it out today for a run and the problem re-appeared after 3-4mins of WOT then back to 30secs then back into neutral to get it back.

sorry for the essay, any help appriciated guys

check your tank vent is not blocked

[martynwilley]

thanks, that was gonna be my last effort tomorrow i am running a small outboard tank directly into my fuel rig

if that doesnt sort it, then i guess it must be carb problem? (as ive replaced everything now before carbs)

[Jay Smith]

Could be tank vent OR the suction side of the fuel pump hoses are sucking air from a leak or srack in line causing the pump to cavitate..Also check fuel filter blockage, always place your more restrictive micron fuel filter on the discharge side of the pump. Pumps are made to PUSH through a filtration system NOT PULL through one..If your going to try and filter fuel before the pump make sure its very free flowing like a screen as a restrictive filter on the suction side will effect pumps performance curve and engine fuel starvation ..

BTW: 6.5 PSI at the carb bowl is a bit much for my liking most needles and seats can't take that pressure and vibration and will flood. I understand thats not your ISSUE at present but I find on our carbed race engines most are more consistant at 4.5 to 5 psi..WE find a flat perco seat more likely to seal than the cone type seats on an outboard with its vibration ...

Cheers,
Jay

[larby]

What came of the issue with the pump not giving any pressure that you called me about? Seems to me the two problems are likely to be linked?

Are you sure that all the wiring and connections to the pump are good and up to the job now?
Is the pump 'quietening down' properly as it fills with fuel? Is it going noisy when you're out and running low on fuel?
As mentioned is there an air leak anywhere that could be dragging air into the system? (this one sounds quite likely to me)

I did suggest last week that you simplify the system by running from a seperate 5ltr tank or similar, this would easily show if there's perhaps an issue with the tank pickup.
I also suggested you take the hose off the carb and run the fuel into a bucket or something with your finger partially over the end (to give some restriction and get the pressure up). This will confirm fuel flow. Assuming all tests out ok and you've already confirmed the pressure is there with the gauge, the fuel delivery system isn't likely to be the issue.

Going back to the carbs, are you sure all is ok and clean in there? If you've got an issue with the floats or a valve or channel blocked, it could be an issue with the carbs not allowing the fuel flow in correctly. Don't forget flow and pressure are totally different things. Some people wrongly assume that if there's pressure there (as shown with your gauge) then there's gotta be flow. Same with voltage and current in electrics. Also just because the gauge registers something on the line, doesn't mean it's all ok in the carb bowls.

Back to the electrics. Thinking out of the box here, the boat is nice and still when idling, but jumping about all over the place when going along (especially with you driving! )
There could be a bad connection or similar wiring issue that isn't showing until everything gets shaken about, so your pump may be cutting out intermittently wehen going along, causing the lack of fuel, but when you grind to a halt it's nice and still so all seems fine. Easiest way to see this would be to hard wire a light to the wires where they go into the pump, then position the light on the dash. if the electrics are flickering, so will the light, or use a buzzer if you don't want to watch a light.
Alternatively, sit tom in the back and get him to watch & listen to everything, I did this for a while with Frank to check everything over. Thankfully not to find issues as I'm incredibly anal about this kinda stuff, keeping everything neat and perfectly finished, which has paid off in the long run with no issues at all to date. (touch wood!)

Hope that helps!

James

[Big V]

6.5psi is way too high

We set ours at 3.5psi and it works nicely

[martynwilley]

ok, so.

took it out for a spin with the fuel cap off to eliminate the tank breather problem- no change

then riged small 25ltr aux tank and it ran really well no bogging, turned the reg down to 5psi and it seems to fuel well, didnt use any trim today, saw just just over 6000rpm an 65mph

gonna rip the fuel tank out (its a really old fibreglass tank) and check the pickup, this must be the cause now??

i have a spare s/s tank in a ring 20 hull i have spare that would fit. what are the advantages/disadvantages of fibreblass/s/s tanks???

thanks for everyones input, looks like im gonna be ready for the race next month

[larby]

The main advantage seems to be that the glass one doesn't work and the stainless one does! I doubt you'd be able to 'fix' the glass one strongly enough so I'd just get to fitting the stainless one.

James

[Jay Smith]

If your buying a tank look at the poly ones from JAZ in the states, they are reasonable much cheaper and lighter than Stainless Steel, be sure when and if you order make sure that its opaque ( Clear ) also get one with a drop in the bottom so you don't have to pull from the top ( thats a marginal way to get fuel to a pump and creates many many supply issues ) the JAZ cells have a knock out on the bottom of the tank which is much lower than the bottom and and has molded in an accelerated steep ramp down to the AN fittings on the knock out.With the knock out much lower than the bottom so baffles are not needed to keep fuel at pick up points. They are a CLASS # 1 ACT to supply fuel in race boats and cars from drag to F-1 I've used them for years as 90% of the folks here do...NHRA Drag Race cars use them also..

Cheers,
Jay

[Big Dutch]

And whilst you are at it I suggest you fit a new throttle cable cos the way you were driving it today it sounded like you were busy wearing the old one out !
Did you smoke the Extreme ?

[martynwilley]

didnt see extreme.
played round with some jet ski's in trident wake and chased adrenalin 4 a bit. wasnt really expectin it to run after the problems id been havin, tomorrow ill get out there with saftey gear an lids on use some trim an keep the foot pinned!!

[andy21]

Originally Posted by martynwilley

didnt see extreme.
played round with some jet ski's in trident wake and chased adrenalin 4 a bit. wasnt really expectin it to run after the problems id been havin, tomorrow ill get out there with saftey gear an lids on use some trim an keep the foot pinned!!

Yeah she was sounding ssssweet!

Makes me want to take a dremil to my exhaust!

[Big V]

"Chased adrenalin 4 a bit"

Did you fly past it?

[andy21]

Originally Posted by Big V

"Chased adrenalin 4 a bit"

Did you fly past it?

Did you not get a GCSE in English Big V?

[andy21]

If you really want to know who flew by who, then i'd say it was pretty level headed and i think Martin will agree that neither of us where going flat out but both of us were having a laugh...

If you really want to turn this into the usual Guernsey 1 up manship thread then we can go down that route then we'll happily play along, but to be honest its a bit boring

[andy21]

and sorry for thread jacking Martyn!

[Big Dutch]

MMMMMMM a bit touchy ain't it ? I think the question was aimed more at Martin but judging by your answer I think we get the picture.
Anyhoo it don't matter Dude not everyone is competitive-apparently

[Big V]

Originally Posted by andy21

Did you not get a GCSE in English Big V?

You really are a cock.

See you everyone, telling some people what they really are is worth getting thrown off bitchmad.com for.

[andy21]

Originally Posted by andy21

Did you not get a GCSE in English Big V?

That was a joke Jacques, Martyn wrote he was "chasing" me and you asked if he "flew past"... The word chase would suggest that he didn't hence the joke about English GCSEs... Whether you did get one or not I don't really care but it seemed to touch a nerve

Thanks for showing your true colours though

[Paul E]

so how's the fuel rig then Martyn?