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3 Stage Power Upgrade

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3 Stage Power Upgrade

Postby Nechako » Wed Sep 12, 2018 8:44 pm

For whatever reason my Meanchicken account was out of commission for a while so I never got to do an update on my boat repower. I've got an 18' Firefish Pirahna heavy bottom and full Teflon. All plascore interior and lexan windows. I originally had a 5.3 L33 and flopro 3 stage in the boat.

Haxby built me a 408 stroker LSA. We did lightning headers.
I changed the pump impellers out to a three blade overlap up front, followed by two 27 degrees. 96 mm nozzle.
The motor dyno'd 705 HP and 730 ft lbs.
At see level I pulled the above impeller combo to 6000 rpm. Wicked cruise speed at 3200 rpm. Spins out if given full throttle below 3500 rpm.
I live in Prince George, BC. I lost 300 rpm at this elevation.

I'm now cut back to a 92 mm nozzle and pulling 5600 rpm. It hangs on above 3200 rpm.

Boat does 60 mph with no current. It porpoised with the 96mm nozzle at full throttle. It does not do this with a 92 mm nozzle but feels like its plowing a bit. Trim nozzle is coming...

There has been a lot of talk on here over the years on three stage power so here it is. I have an honest 2000 rpm from a great cruise speed and when you hammer it things happen quick. It is a ton of fun to say the least!

Let the questions begin...

:Drink:
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Re: 3 Stage Power Upgrade

Postby akhunter67 » Thu Sep 13, 2018 7:38 am

At what rpm is 705 hp! Sounds like a lot of fun!
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Re: 3 Stage Power Upgrade

Postby Kilowatt » Thu Sep 13, 2018 8:52 am

:Worthless: :Worthless:

Love to see some pictures of your boat, I'm also in PG (and just sold my Piranha). Hammerhead on the way.
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Re: 3 Stage Power Upgrade

Postby riverboater » Thu Sep 13, 2018 4:34 pm

pm sent
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Re: 3 Stage Power Upgrade

Postby Nechako » Thu Sep 13, 2018 9:24 pm

We dyno'd to 6000 rpm. Peak torque a bit lower but it was making big torque down low. Well over 600 ft lbs below 3000 rpm.
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Re: 3 Stage Power Upgrade

Postby Nechako » Thu Sep 13, 2018 9:32 pm

Boat4.JPG
This is prior to final touches and interior finishing but it is essentially the same today
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Re: 3 Stage Power Upgrade

Postby prd » Fri Sep 14, 2018 5:58 am

So what is your cruise speed? Is 60mph your top speed? That looks like a hell of a fun boat, kinda a sleeper. My outlaw sport does 50mph with a delta bottom and full gas and a decent load of people and junk with a 351 and a stainless double A at 4000rpm. A little more detail would be nice to figure what a shallow water boat does with a high Hp motor. If you don't mind why did you do this engine build for that boat? Cuz you could? Cool anyway.
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