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mlange

Perfect Pass Question

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mlange

Today was the first day I was able to actually ski my new (used) RLXi. The first time out I ran into an issue with the fuel pump and took it right back to the dealer. While it was in there they also installed PP for me - they were waiting for it to come in when I picked up the boat the first time around.

Anyway, with the Black Scorpion I am only turning 4650rpm at WOT. Obviously that is not enough. Before bringing up a potential incorrect propping issue, it is the ACME 515 prop, so it is definitely prop'd correctly.

So, at this point I think there are two possibilities.

1 - The engine still isn't getting enough fuel pressure to run at WOT.

2 - The PP install has an issue and is "limiting" the engine and not actually opening up the throttle all the way.

Does my PP theory hold any water?

Thanks,

Mike

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CarveItUp

The only issue I can think of re: PP would be if the PP cable was binding and somehow prevented your throttle cable from pulling to wide-open.

PP exercises speed control by throttling back from the throttle point you set with the throttle arm. It has a servo that can release the throttle cable a certain amount and pull it back in. It can never give more throttle than you've initiated with the throttle arm.

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mlange

Well, that's kind of my question. I know that PP works by "throttling back" from where the throttle arm is, so I'm wondering if there could be an issue where, even with PP off and the throttle arm all the way forward, that the throttle cable isn't actually moving through its full range of motion.

I also came up with a third option that maybe the flame resister is real dirty and the engine isn't getting enough air to breathe.

Mike

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RTS

My bet would be the fuel pump. What did the dealer do to it? Does it squeal? A couple years ago, when my first pump was going bad, I could only get about 4300 RPM ("normal" WOT for me, with a good pump, is right at 5K RPM).

Incidentally, the RPM would sometimes "porpoise" up to the 4300 RPM, i.e. Up to 4K, down to 3.5K, up to 4.3K all with the throttle wide open. Is yours doing this at all??

Edited by rts

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mlange

Nope. But I stretched the truth a bit on it being the fuel pump. On a Black Scorpion there's a pump and a "booster" pump. The booster pump is what's bad. It's supposed to help with combating vapor lock.

I should have been more detailed the first time around, but I was in a hurry to get the post up and my wife was nagging at me to help out with our son. Sorry about that.

Anyway, they were able to replicate the issue right away when they lake tested it and saw with the computer hooked up that it was losing fuel pressure. The tech then kocked on the booster pump a bit and it sprung back to life. They had to order out for the booster pump and I didn't want to wait. So, I put the boat in yesterday and did some skiing with no noticable problems besides the lack of turning enough RPM's at WOT. The tech is going to come out to the lake this week after the pump is in.

I'll just tell the tech to make sure it's running around 5000rpm after he puts in the new pump and have him work the issue if it doesn't.

Thanks,

Mike

Edited by mlange

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Faceplant409

When I added pp to my old boat I played with the throttle linkage for a while before I was happy with Idle and WOT. I could get one right but the other would suffer. And vice versa....

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