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What does it take to go 80mph???

Gelcoater

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Hypothetical............

Lets say I have a 21-22' open bow jet boat. I'd like it to do around 80mph. My questions are, how much work needs to be done to the pump, how much power is needed, and would there be a huge speed difference between loaded and empty?

Thanks.
so did you ever get one?
 

BONER

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so did you ever get one?
No. I had a baby since I started this thread and unless a Daytona, I don't think a 21 or 22 will be big enough. And if I were lucky enough to own a Daytona, it would be twin OB or blown mountain motor.
 

lbhsbz

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No. I had a baby since I started this thread and unless a Daytona, I don't think a 21 or 22 will be big enough. And if I were lucky enough to own a Daytona, it would be twin OB or blown mountain motor.
15 years ago I put a pump together with a hardened shaft, SS impeller, new Dominator suction housing, new Dominator bowl and a used place diverter/nozzle for about $2000. Today those parts are closer to $6000...probably more.

Making a squirt boat run is more about setup than it is HP....I think. When I put my old shitbox sorta-tunnel squirt boat together...it ran 68mph. I got it into the high 90s without pulling the valve covers off...just pump work and setup.

Kinda like my MOD VP outboard I suppose...trimmed down with the engine buried it'll run in the high 50s....if I jack the motor up and give it some trim...82mph+...with a 35 year old worn out 200hp merc.
 

BONER

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15 years ago I put a pump together with a hardened shaft, SS impeller, new Dominator suction housing, new Dominator bowl and a used place diverter/nozzle for about $2000. Today those parts are closer to $6000...probably more.

Making a squirt boat run is more about setup than it is HP....I think. When I put my old shitbox sorta-tunnel squirt boat together...it ran 68mph. I got it into the high 90s without pulling the valve covers off...just pump work and setup.

Kinda like my MOD VP outboard I suppose...trimmed down with the engine buried it'll run in the high 50s....if I jack the motor up and give it some trim...82mph+...with a 35 year old worn out 200hp merc.
From what I've been learning, you're correct about setup, but that seems to be the case with anything.

But I feel like the longer the boat, the slower it will go with a jet? Is weight a huge enemy of jets?
 

wzuber

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From what I've been learning, you're correct about setup, but that seems to be the case with anything.

But I feel like the longer the boat, the slower it will go with a jet? Is weight a huge enemy of jets?
Yes, as it is in all things. Hull bottom design is another significant factor. Lifting strake size, length and configuration, keel shape and entry @ intake all play a very big role in hull speed potential, stability and efficiency. Look at the Wreidt 21' cruiser hull bottom from the 70's. That hull ran fast and stable for it's time and would be still today. In the early 80's Tom Roland started a boat Co. called Royale Boats. Their 1st and only model developed was a 21 cruiser that utilized the Wreidt 21' bottom w/ a newly tooled deck for the times styles. His first hull built weighed 950#'s bare and was laminated by Merril Combs @ Aqua Craft boats in Riverside. (Circa 1981-ish)
It was solid yet light for a boat that size. Tom installed a full set back, stock Dominater eng/pump w/adj. Shoe etc. and 420 hp. Eng. Package with thru transom lightning headers. The river duty complete boat ran 72 mph. In the 1/4 mile @ njba @ blue water first lap off the trlr. Tom knew how to set it up from his UBFJ drag boat program.

That's an example not too far off your desired goal with relatively modest h.p.
That boat popped up on perf. Boats sight a couple years ago and was being restored at the time. You could search it there if you're interested. The mold was aquired many years later by Steve Strange and built and sold as Pro Boats. He turned it into a tunnel. There was a guy on P.B. that had one for sale.
 

wzuber

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Bare hulls for general population and river play I would say as light as 400# up to 8/900 on the heavier/bigger side. I would bet yours is in the 600- 700# range.
No I mean a complete boat rigged
Bare hull 600#, all iron BBC. eng./pump 1300, empty tanks 40#, 2 wood/vynil buckets 60#+, rear bench 75#, full carpet 20#, deck hardware, gauges, steering. cables, foot throttle, diverter etc 200#. Roughly 2300-2400# add for fuel load.
 

Blackmagic94

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Guess I should bust out my aviation scales and see how heavy it is on the trailer
 

Blackmagic94

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Update.

71 mph at 1550 feet at lake pleasant on a 78 degree day

5100 rpm
4.5-5.0 psi boost
AA impeller
 
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