How to check sniper EFI fuel pressure
 

I have a problem with what I think is fuel delivery:

21' Scarab 1 w/ 505bbc, 28" standard bravo 1 prop attached to a stock bravo 1 out drive. I will post the dyno results in a pic below, makes 560hp@5200 and 630tq@3700

I am only seeing about 3800rpm, I can't get any more out of it. I confirmed the throttle has full swing and hits the stopper on the sniper. I am running 3/8" supply and return lines, using the Holley external in-line pump. Holley says to test fuel pressure at the inlet of the sniper to confirm 60psi, but how do I do this while WOT? Is there too much restriction?

Tank -> pickup -> pre filter -> pump -> post filter -> fuel/water filter -> sniper
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what else could cause low rpm? The boat pops up on plane and has no issue with throttle or bogging, it's as if it has a rev limiter at 3800 Would love any insight! Have not tried any other props

Thank you!
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https://cimg6.ibsrv.net/gimg/www.off...58ce25a404.jpg

How did you set the pressure for the fuel pressure regulator and return line??

I’m interested in your answer to griff.

im not running Holley but I’m running efi. I’d highly suggest a fuel surge tank. I’m pulling from my two tanks via a low pressure pump through water filter separators. From the surge tank I’ve got the high pressure pump through a pressure regulator and return fitting back to the surge tank. All my fittings are AN fittings so it’s very good connections.

I don’t see a need for a fuel cooler at the moment but I’m definitely keeping an eye on it. Depending on what we find out from above you may want to consider how much stress is on your fuel pump and if you are not getting the best delivery due to boat ride characteristics. Such as regulator, pump, fittings, hoses etc…

It's in the instruction page 6. Hook up a mechanical gauge and watch it while you are running.

https://cimg3.ibsrv.net/gimg/www.off...ec36d9de7c.jpg

depends on the version. the original sniper has a built in regulator, the sniper two needs an external regulator in the return line.

I've read that, which is what prompted my question - it's going to be tough to read pressure at 3800rpm which is ~50mph with my setup

Maybe I'll have to recruit someone to crack and hold the hatch and watch the gauge

​​​​​​My version of the sniper has an internal regulator set at 58.5psi, what I didn't know is I also need a regulator in the return line the previous comment suggested? Right now it's running straight back to the tank

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Re-reading what he commented I think he's referring to the sniper 2, my manual never stated anything about needing an external regulator of any kind

original sniper just run from the return port to the tank. on the new sniper two there is no internal regulator so you have to run a regulator on the return hose. go buy a mech fuel pressure gauge and hook it an unused port on the water fuel separator and run a hose up to the dash area. it can be the small plastic hose as it is only temporary.

Will do, just bought a mechanical oil filled 100psi gauge on Amazon, I won't be able to test until the cold is over but will keep everyone updated. Hoping it's as simple as swapping to a more powerful pump

when you say it has full throttle movement is the screen showing 100% TPS? does the screen show the same 3800 rpm as the tach. also is this a new install? does it have an anti siphon valve? you may have a fuel hose failing between the tank and pump or the anti siphon is too much restriction for the pump. if all else fails get a 5 gal jug and run a new hose from it to the first filter to take the tank out of the equation and see what happens. this all assumes the fuel pressure drops off above 3500 rpm.

I don't know anything specific about the Sniper system and didn't know about it having an internal regulator.
What I posted is generally how most efi's are rigged. The external regulator bleeds off the excess fuel pressure into the return line.
Your regulator must be internal and close to the fuel return line connection.

if you look at the pics above of the sniper 1 you can see the 4 screw cover on the one marked return. that is the regulator. makes for a clean install so why they chose to change the sniper 2 to require an external regulator in the return hose is anyone's guess as they do not include it in the kit so after you buy it you find out you have to order something else to finish it with.

You have a phone that takes video, right ?
Or a gopro available ?

Edit in: you pull your spark plugs to see if anything is being eatin’ ?

If you put a fuel pressure tester on it and it does read low, you will still have to determine whether its the fuel pump not making enough pressure or if its the regulator opening and bypassing fuel at too low of pressure.

I'll have to rig a GoPro to it somehow, all of my mounts are screwed into the hull, I don't want to do that to the inside of the engine room

The unit is brand new but I wouldn't be surprised if the regulator is faulty. I still suspect the fuel pump is cavitating or simply too weak / too much restriction. Thanks for the suggestions. Once the cold is over I'll hook up everything and see what the gauge reads!

id check your key on pressure just to see if its even close, if its a bran new unit you need a external regulator as per the instructions.
hows your A/F sensor mounted. is its reading properly? when mine when bad it did a bunch of weird shat.

not to hard to check fuel pressure well under way, most pressure gauges give you a foot or two of line so you can route it outside the hatch and have someone watch it well you get on it

The fuel pressure tester I got from Harbor Freight similar to this one had about a 4' long hose Basic Fuel Injection Service Kit (harborfreight.com)

I ordered an Earl's oil filled 0-100psi pressure gauge and AN adapters to hopefully get a good reading. I dropped my riser off at a shop and he installed the bung at the top of my riser clocked at 2
https://cimg5.ibsrv.net/gimg/www.off...e5fc6c144a.jpg



If my setup doesn't work I'll order this kit, priced very well.