Am I in the ballpark?

[roostwear]

In my never ending quest to blaze (?) past 70mph, I gotta get some feedback. At CBBB, I finally had a tach that worked(!) and GPS'ed the circus boat.
My setup
Berk "A" impeller
"Warm" 460 BBF
Cam is a CC 280h
Stealth intake, Holley/Proform carb
TT logs
Berk "E" pump (ramp loader, stock cav plate,no shoe) rebuilt by Jack last summer.
Rogers bubbledeck-like 18'
Full tanks (24 gals)
Took the damn bimini off for speeeeed.
So much for the details. On Saturday in the chop, I GPS'ed at 61.2 at 4700 rpm. Previously, I GPS'ed at 68.2 on glass. I assume the rpm was the same, but that was before match porting the logs, so I can't say for sure.
Am I in the ballpark? The shoe and rideplate is on the way, but anyone have any other reasonable suggestions?

[LVjetboy]

4700 w/a Berk A is a bit low for a mild 460 BBF but not unreasonable with logs. For that power and 61 mph on an 18' jet I'd say a bit slow. But not unlikely.
Do you have trim? My guess's at that speed, shoe and rideplate may be no big deal. Also, your gps 68.2 and 61.2 mph don't jive...unless way differnent conditions. Don't forget river current good for as much as 3 mph if GPS's instead of pitot, and weather variables add to the uncertainty. To measure small changes like shoe or ride plate at that speed you need to do back-to-back testing with accurate measurement.
All that said, to reach your goal of 70 mph with your hull...u may need more power.
jer

[roostwear]

The conditions were radically different. 68mph gps downriver (adjusted for current) was on glass in 100deg low humidity, 61mph gps downriver (unadjusted, approx 3 mph current) on 12" chop overcast 95deg and high humidity. I have a Place diverter, both runs trimmed.

[HavasuDreamin']

This may not be the case, but is something to think about. I ran the gun at a local radar event about 5 years ago. I saw a lot of jet boats and outboards run up close. One guy with a mild big block, semi-v jet radared somewhere in the mid 50's. I thought the speed was quite low for an 18' jet with OTT headers and a mild dual quad set up. He ran through several times. His boat was plowing water big time. It was breaking the water up near the front seats. He did have a diverter. He was still plowing and he had no clue how bad.
My guess is he had a major hook in the hull. Moral of the story.........if you can get someone to view how your boat is running at speed and how wet you are, you will have more info. with which to work. You may have a hook, you may not, but a straight bottom is crucial to get less wetted surface........especially when you start adding power.
Good Luck.

[roostwear]

My hull does not have much if any hook, and rides fairly dry. It cuts behind the front seats. Randy has seen my set, so he knows what it looks like better than me. The intake sits 3/8" above the keel which is why I'm adding the shoe and ride plate. This seems fairly typical for an E pump. I'm looking for more lift and a better bite at the intake. With more lift at the transom and trimming up the bow, I beleive it should run dryer. It is an open bow, so I have a little extra weight on the bow, but it hasn't seemed to be a big issue.

[roostwear]

Here's a shot of the 61mph run at CBBB (thanks Chris and Tyson!)
It's not running all that wet, but I'd like to see the transom lift a little.
http://www.***boat.com/image_center/.../896cbbb3b.jpg

[victorfb]

mike, by looking at that pic my guess is that you are having to keep the diverter down too low. your thrust line my be a bit too low and causing your bow to come up early then want to slam down because of lack of speed (and weight). can you raise the thrust line in any way? do you have a pic of the pump set up?