CheckmateScarab

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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Griff

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

Xcomunic8d

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…

Rookie

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

compedgemarine

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

CheckmateScarab

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

CheckmateScarab

​​​​​​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

F-2 Speedy

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CheckmateScarab

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

compedgemarine

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.