Rpm's not matching speed ???

[Checkmate]

Well I took my boat out for the first time this year since I rebuilt the pump. Boat pulls alot harder than it used to, but top end dissappointed me.
Last year I got 57 mph on the gps. This year I got 59.7 on the gps. Granted, I only made a few conservative runs since it was the first time out and their wasn't too many boats out there in case I had trouble, but I was hoping for at least 65.
Anyway, what makes me curious is how I am getting 5000 rpms out this motor and only getting 60 mph out of it. Is it possible that the tach be off that much? I am using the tach lead off of my MSD6AL box.
The impeller I am running is an Agressor B cut which I am told is basically a Berk A cut, So IF I was actually able to push 5000 rpm's wouldn't ya think 60 would be a little low on the speed ?
:confused:

[sidewound]

Might wanna check that rpm with a tach/dwell meter at the source. At least you'd know if the tach's right. I have the same suspiscions about my tach but since I'm busted I aint doin anything with the boat.
Peace Man!:cool:
CESAR

[riverbound]

Sorry to jack the thread but, Sidewound how is the recovery going?

[squirt]

5,000 rpm with a B aggressor puts you at about 400hp using the berk. chart for an A impeller. Is this about what your motor makes? Speed is more a function of weight/ drag and has less to do with rpm. Not sure what size boat you have or how it rides but it could be right.......or not:D
Don

[Checkmate]

Not exactly sure about the hp, never dynoed it, but the engine builder that built it for me figured around 470 hp with headers. I am currently running logs so they are robbing me of power. Possibly the hp may be there. I just hoped for more speed out of this damn thing. I am going to remove the homemade loader grate and put the stocker back on and see what happens.
Funny thing is that my old impeller was beat up pretty bad and this impeller really pulls hard compared to the old one, but if the difference is so great, then why the hell am I only seeing a 2.7 mph increase in speed?
I also suspect that the air induction has a little to do with it also, I forgot the bolt for the flame arrester and ran it this time out with nothing on the carb. I am hoping that this played a small part in my dissapointment.
I will not rest til this thing is running solid in the high 60's. 70 would be nice, but by the looks of it, a long shot. I think this hull is the bad link.

[327,jet]

Just remember that 460 is a large piece of iron. They make a lot of torque but are heavy.A 3 M.P.H. improvement is not that bad, for a pump rebuild. Does the boat have a diverter? Also a loader grate might pick up more top end. How big is your Checkmate. The R.P.M.'s sound about right to me .

[Checkmate]

Just to update this thread, I took it out again and this time ran 5,100 rpm's and 65 mph. A little better, but still not great. Looking for more !!

[Squirtcha?]

Originally posted by Checkmate
Just to update this thread, I took it out again and this time ran 5,100 rpm's and 65 mph. A little better, but still not great. Looking for more !!
To what do you attribute the gain?

[roostwear]

I don't know what you're expecting out of a jf pump. I have a JE (insert also), and GPSed at 68.3 last time I checked. I've been working on my setup, since more speed via HP gets expensive at this point. When I pass 70mph, I'm done tweaking this boat. I can build more speed cheaper in a JG pumped boat.
Come to terms with the limitations you have. The fastest insert style boat Jack could recall is 80 mph. I don't know about you, but I'd rather build another boat with the cash it'd take to go 10mph faster!

[Mohavekid]

Just an FYI, there's a guy here, Fast Sanger,l that claims mid 90's out of a Sanger Mini-Cruiser and a Berk "e".
The insert style can be made to run. I'm betting your hull and setup have more to do with your current speed than your insert style pump.

[roostwear]

With all due respect. I think that guy can say whatever he wants, but let's see the proof. I have what is basically a Rogers 18 bubbledeck with an E, so it's not like it's a slug. Can it go faster? Sure. The point was, it takes a LOT more money to do it. Ever look at the casting of an E? It's THIN compared to a C/G. Not even much meat to mount a shoe to. Why beat your head against he wall for a pump with an acute intake angle, and the ride plate sits above the keel line? Boaters will spend their money on whatever their ride is, but if someone REALLY want speed, use some common sense. Don't start with a handicap.

[Mohavekid]

Roost, I never said the e/f pump is the hot ticket.
What I said was that there is more to be had than 65mph out of a well set up boat with an e/f pump.
Yes, if he wants to build a boat to compete with the fastest boats out there, he'd better start with a different hull and pump combo.
I doesn't sound like that's his intent. He wants a little more speed than he has now, some set up work with the pump he has now might help achieve that goal.
First, I'd look for some hook in the hull. If the hull is straight, try adjusting your ride plate up allowing the boat to air out some. The f trim or a place diverter will help too. If the boat is still riding wet, and you want to swap to a two piece bowl, you can try a droop to get some more lift on the bow.
If you don't have a loader, adding one might get you some more MPH as well.

[pops1]

The Impeller -the cut to rpm's says you should be higher yet.

[Jet Hydro]

Originally posted by Mohavekid
Just an FYI, there's a guy here, Fast Sanger,l that claims mid 90's out of a Sanger Mini-Cruiser and a Berk "e".
The insert style can be made to run. I'm betting your hull and setup have more to do with your current speed than your insert style pump.
I have to question this claim. Not saying that it cant be done.
I have a 12-je in my lake boat, it`s a real Turd of a boat but will run 80`s with my spare race motor in it cut back with 2-600 holleys on 91 pump gas. I plan to do one of two things to this boat during the winter, #1 cut the opening up on the bottom of the boat and make it more square and bigger like an intake or #2 install a real pump :D
Never the less this boat is heavy and will run in the 80`s with a HI-Techperformance ware ring <--- ( just for chet ) :D Berk ( B ) at 6000 rpm`s with a stock Dom nozzle and bowl.

[Checkmate]

AS for my trim, I have the factory F trim, but the only thing original on it is the cable and controls. Everything after the cable has been reworked to perform as well as a Place diverter. (benefits of a machinest as a father)
I hadn't thought about the "ride plate" I DO believe that I need to get the boat out of the water a lot more than the trim will do. Should I adjust the factory plate up some, Or should I have a new one made that is bigger, more of a true ride plate. If so, what is a good size? I have been replacing all the bolts and the steering parts on the pump with stainless, so if I had to rebuild a rideplate I would use stainless for that too. How thick??
Sorry for all the questions, but I WANT to exceed 65 with ease this year. (without it being on the trailer:D )
Also, I have been experimenting with a loader setup. I made one that did absolutely no good, but I believe it was because what I made was not a top loader, but more of just two small angle iron tabs about 2 inches long that did not extend into the intake past the fingers. Would this pump benefit greatly from a top loader at these speeds? Since have no local shops around I was just going to make my own experimental pieces and if I got the combo right, good, If not, no loss.
I appreciate ALL feedback and look forward to the replies, Thanks, Dan

[Checkmate]

Originally posted by Squirtcha?
To what do you attribute the gain?
I believe the gain would be because I was more into the pedal and working the trim. The last times out I didn't really waqnt to push it since I was basically alone if something happened, this time I was not worried about the engine, been running flawlessly.
Knock Knock ....;)

[ssanddemon]

Don't you want to crank that plate down to lift the boat? I have an E type Amercan Turbine and had a real bad porpise until I put a good downward tweak to the plate. I'm not looking for top speed though, just a clean ride. My factory 460 with A imp. did about 55 @ 4200 rpm.

[roostwear]

You might find this enlightening. Take a long straight edge (4'), run it back from the keel, and see how high the rear of the intake/plate is from the keel. Mine is about 3/8". I installed a ramp loader from MPD, and MIGHT have picked up 1-2 mph. Brought the ride plate up to 4 degrees, and it HATED it. Porpoised it's ass off!(didn't porpoise at 0 deg) Dropped it down to 2 degrees and it is a bit looser, and may have picked up a little. The whole point being, your hull will react differently than mine did, but put a little time in tweaking it, and you'll get a little more out of it. HTP makes what looks like a nice shoe/plate combo that you might consider. It looks like it will bring it down to the keel line and provide more bite at speed. Like the saying goes... speed costs money , how fast can you afford to go? I'm satisfied with my setup the way it is..... I'll spend the money that this boat would need to go faster on another, better suited boat.