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3.5 cc Tunnel Hull vs 7.5 cc Tunnel Hull

Old 04-14-2006, 01:48 PM
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Bullitt01
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Default 3.5 cc Tunnel Hull vs 7.5 cc Tunnel Hull

At this time im putting together a Top Speed 2. I was wondering about the difference between a 3.5 tunnel and a 7.5 tunnel? I know the physical differences (larger hull, bigger engine). But i have questions like; is the 7.5 faster? Handle better? Do most guys run 3.5s? Is the 7.5 more of a advanced tunnel boat?

Thanks!
Old 04-14-2006, 02:07 PM
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Ron Olson
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Default RE: 3.5 cc Tunnel Hull vs 7.5 cc Tunnel Hull

The 3.5's are in more plentiful supply as long as a choice of engines. In stock form with 7.5's you have only one powerplant.
New boaters find them a good place to start and the cost of course is a lot lower also.
Advances? Not really, as they both are using the same technology.
Old 04-15-2006, 08:58 PM
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Default RE: 3.5 cc Tunnel Hull vs 7.5 cc Tunnel Hull

I have driven both size OB tunnels(stock K&B)

I find the 7.5 hull can handle waves much better. I can jump full scale waves with out flipping. Can't do this as often with the 3.5 hull as it flips easier.

Speed, The 7.5 was faster than the 3.5 hull I drove, but the new top speed 2(with O.S.) can keep up with my 7.5 with ease.

As far as being advance I don't see how.
Same factors affect both the 7.5 and 3.5 hulls.

Small disadvantages/Advantages of 7.5 hull. (opposite for the 3.5 hull)

-Louder
-More of a "roar" sound than high pitched scream
-For some reason more people approach me when I'm using the 7.5 hull
-see it better when it's further away


-A gallon doesn't last as long

Ryan

Old 04-15-2006, 09:06 PM
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piper_chuck
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Default RE: 3.5 cc Tunnel Hull vs 7.5 cc Tunnel Hull

I think the biggest difference, other than size and speed, is that there are way more people running the 3.5 tunnels. Unless something is done about engine and hull availability, that's unlikely to change. If you're looking to get into tunnels, 3.5 offers more opportunities to race than the larger ones. If you just want something to run at the lake, the larger sizes have advantages.
Old 04-15-2006, 09:57 PM
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Default RE: 3.5 cc Tunnel Hull vs 7.5 cc Tunnel Hull

Very true. It's rough to see/hear the 7.5 hull(because of engines) suffering in popularity.

Ryan
Old 04-15-2006, 10:11 PM
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ob nut
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Default RE: 3.5 cc Tunnel Hull vs 7.5 cc Tunnel Hull

I've been running 3.5 for years. One 7.5 was in the collection at one time. I've recently have built 2 34" WOF's. Powerplants will be either both 7.5 or one 7.5 & 11cc motors. Being built now is a Nelson 7.5 ob motor, which I should have at the next K-Zoo Fun Run. All motors will be equiped with pipes that have internal stingers to reduce noise. If you want noise, run a stock 11cc or larger K&B. Have ear muffs. Agree with what has been said about the 3.5 vs 7.5 already. 7.5 will out perform a 3.5 on most days. One must compare apples to apples though. Think my 29" WOF will give a stock 7.5 a run for it's money. Last test day with the 29" WOF had a one pass of 56.3 mph. On that tank, most passes were around 52 - 54 mph. Boat info: 29" WOF, stock MAC 3.5, Lawless lower with presure oil system, SPP pipe, s/b x440 prop, 65% Wildcat fuel. The 34" WOF's are not completed yet so no speeds to compare them to the 3.5. Those will be done once I'm back from a business trip.
Old 04-16-2006, 11:20 AM
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Default RE: 3.5 cc Tunnel Hull vs 7.5 cc Tunnel Hull

Thanks...youve all been a great help!

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