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Discussion Starter #1
Boat - 86 Mantra 16' Tunnel (305lbs hull) very similar to CP Tunnel and Texas Tunnel bottoms
Engine - 440" BBC (nothing too special, guessing 550hp ish)
Pump - 1994 American Turbine with a B impeller

No droop. No diverter. Center blocker loader. No inducer. 3.125 nozzle. Currently has a 5 degree wedge.


The boat runs really wet it seems. Before the 5 degree wedge, it was running in the water up to about the drivers seat. Now it runs in the water at about the back seat. It runs pretty strong up to 4200ish rpm's and hits kind of a flat spot for a second, and then pulls to 5400rpms and that's all she will do. I'm not sure what mph 5400 is with a B impeller, but I feel like it should turn a little more than that as small as the boat is. Am I wrong thinking that?

How do I measure for all of the items in the pump setup? It's a radius keel, not a flat keel. Do I measure off the bottom of the radius? The side where it's flat? Where do I go from here?

How far should the loader hang down?
Should I put in an open loader?
How far should the shoe hang down?
No droop/Full droop/Mini droop?
Diverter?
Nozzle size?
Ride plate angle?
Wedge or no wedge?

On this short of a boat, how dry or wet is it ideal to run?

It did pick up quite a bit when we went from no wedge with the pump aiming 4 degrees down, to adding a 5 degree wedge in it....I'm slowly learning about these boats, but still very new to it all. Thanks for any help!
 

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Boat - 86 Mantra 16' Tunnel (305lbs hull) very similar to CP Tunnel and Texas Tunnel bottoms
Engine - 440" BBC (nothing too special, guessing 550hp ish)
Pump - 1994 American Turbine with a B impeller

No droop. No diverter. Center blocker loader. No inducer. 3.125 nozzle. Currently has a 5 degree wedge.


The boat runs really wet it seems. Before the 5 degree wedge, it was running in the water up to about the drivers seat. Now it runs in the water at about the back seat. It runs pretty strong up to 4200ish rpm's and hits kind of a flat spot for a second, and then pulls to 5400rpms and that's all she will do. I'm not sure what mph 5400 is with a B impeller, but I feel like it should turn a little more than that as small as the boat is. Am I wrong thinking that?

How do I measure for all of the items in the pump setup? It's a radius keel, not a flat keel. Do I measure off the bottom of the radius? The side where it's flat? Where do I go from here?

How far should the loader hang down?
Should I put in an open loader?
How far should the shoe hang down?
No droop/Full droop/Mini droop?
Diverter?
Nozzle size?
Ride plate angle?
Wedge or no wedge?

On this short of a boat, how dry or wet is it ideal to run?

It did pick up quite a bit when we went from no wedge with the pump aiming 4 degrees down, to adding a 5 degree wedge in it....I'm slowly learning about these boats, but still very new to it all. Thanks for any help!
I'm no expert, but I have a few questions. What angle do you have your rideplate set at currently? What kinda shoe? Flat, tapered, backcut? Where is it in relation to the keel? Why no diverter? Seems the simplest way to adjust your ride attitude.
And about your rpm's, I could be wrong but I believe rpm has everything to do with the amount of power you have to turn the impeller and nothing to do with the size of the boat.
 

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Discussion Starter #4
I believe the ride plate is 4 degrees up

I don't know what flat, back cut, or tapered means?

I thought at first the shoe was 3/4" below keel, but that was measuring from the flat surface beside the radius of the keel...then somebody told me you had to measure from the bottom of the radius of the keel. I'm not sure if that is true. That is one of my questions.

I'm VERY new to all of this, but I do know that with the same HP and same boat if you get more of the boat out of the water and reduce drag, you'll go faster and turn more RPM's.

Maybe my setup is right, and I need a bigger motor? I just don't know what is right and what is wrong.
 

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I'm VERY new to all of this, but I do know that with the same HP and same boat if you get more of the boat out of the water and reduce drag, you'll go faster and turn more RPM's.

I believe the engine will only spin as many RPMs as the impeller will allow.
 

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start by getting the keel level while using a 4ft level and the front trailer jack, do your measurements off the bottom keel line for rideplate degrees and shoe measurements. the loader bolts into the intake and is at a set amount of drop depending on which brand of loader you have... on a side note, when installing your loader its a good idea to drill the 4 mounting holes through the housing, retap and install longer bolts with lock nuts.

i too would also recommend a place diverter, it allows for instant adjustments. as for droops, i thought they were more for helping heavier boats get up on plane, instead, i'd look into a snoot from HTP. i put both of these on my 19ft mantra and took off a droop, i really liked the results...
 

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Is the pump set back? i know probably a dumb question but just double checking. Also, give us some specs on the motor. Cam, heads, carb, intake. Measure off the keel for your shoe and ride plate. 4 degrees on the ride plate is a good place to start. I personally like the Place Diverter more than running wedges. Its a lot easier to adjust the ride as your running than it is to wedge, then run, then wedge, etc. Also, it takes POWER as well as proper setup to get the boat way up out of the water. What are your goals for this boat? Sounds like you need to GPS this thing as well to get MPH. If you know your MPH, your impeller size, and your RPM, that will tell you a lot about the condition of the pump as well as if you need to build more power to get your goals. But again....what is your goal for this boat? Happy 4th by the way:usa:
 

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I believe the ride plate is 4 degrees up

I don't know what flat, back cut, or tapered means?

I thought at first the shoe was 3/4" below keel, but that was measuring from the flat surface beside the radius of the keel...then somebody told me you had to measure from the bottom of the radius of the keel. I'm not sure if that is true. That is one of my questions.

I'm VERY new to all of this, but I do know that with the same HP and same boat if you get more of the boat out of the water and reduce drag, you'll go faster and turn more RPM's.

Maybe my setup is right, and I need a bigger motor? I just don't know what is right and what is wrong.
Take a look at this site and see the difference between some of the shoe types:
http://home.pacbell.net/jmcclure/ShoePlate.html
Yes, measure from the keel at it's lowest point to determine where the shoe is in relation to keel.
Also, you need a digital angle finder that has a 'zero' feature.... if you don't already have one. You can get a 'Husky' model from Home Depot for around $40. This is how you'll determine rideplate and nozzle angles relative to keel.
On the rpm's....I don't see how airing your boat out more is gonna make your engine turn the impeller any faster. The reduced drag will result in more speed, but not more r's. Again, I could be mistaken, but I don't believe anything is gonna give you any additional rpm's (with the same impeller) other than additional power or cavitation.
Hopefully someone like BP or CS will chime in here and enlighten us.
 

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yep

[ QUOTE=75 TX;1443890]Take a look at this site and see the difference between some of the shoe types:http://home.pacbell.net/jmcclure/ShoePlate.htmlYes, measure from the keel at it's lowest point to determine where the shoe is in relation to keel. Also, you need a digital angle finder that has a 'zero' feature.... if you don't already have one. You can get a 'Husky' model from Home Depot for around $40. This is how you'll determine rideplate and nozzle angles relative to keel.On the rpm's....I don't see how airing your boat out more is gonna make your engine turn the impeller any faster. The reduced drag will result in more speed, but not more r's. Again, I could be mistaken, but I don't believe anything is gonna give you any additional rpm's (with the same impeller) other than additional power or cavitation.Hopefully someone like BP or CS will chime in here and enlighten us.[/QUOTE] I just ran my boat with the new diverter and gained 10 mph no change in rpm but getting the boat dry had huge results in speed but not rpm. I would get a diverter ya a little pricey but I gained 10 mph in a 20' sleekcraft I would start there then add other stuff later!!!
 

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I believe the ride plate is 4 degrees up

I don't know what flat, back cut, or tapered means?

I thought at first the shoe was 3/4" below keel, but that was measuring from the flat surface beside the radius of the keel...then somebody told me you had to measure from the bottom of the radius of the keel. I'm not sure if that is true. That is one of my questions.

I'm VERY new to all of this, but I do know that with the same HP and same boat if you get more of the boat out of the water and reduce drag, you'll go faster and turn more RPM's.

Maybe my setup is right, and I need a bigger motor? I just don't know what is right and what is wrong.

Is this a race boat or lake boat ??

Man if this is your 1st boat just be careful, its gonna do EVERYTHING quick .. 305 lbs hull belongs on a race track, not out on the lake .. Main thing is do 1 thing at a time and see how the boat responds and record in a log what you have done .. Boat should haul sum azz and not need alot of HP to do it ... JMO Good luck :)hand
 

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Discussion Starter #11
TNYoungblood.... It's a lake boat, so far it's manners have been pretty good.


To whoever asked about the style of my shoe.... Looking at those pics, it's tapered.


Still have no measurements yet on anything else
 

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TNYoungblood.... It's a lake boat, so far it's manners have been pretty good.


To whoever asked about the style of my shoe.... Looking at those pics, it's tapered.


Still have no measurements yet on anything else



You got a Tater Chip ;) Be safe bud :D

And Get yourself a divertor, best $$$$ you can spend at this point
 

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Discussion Starter #13
I like to refer to her as my kneeboard with a big block Lol

I've been very suprised with the manners of it. I guess because it's so short, the deck doesn't wave at you at all going across the lake. Becuase I have no diverter, the worst manners it has, is it will porpoise up till about 40mph and then it settles down and rides okay. Been fun so far. Makes my girlfriend nervous though, she's used to bigger boats. She wants me to buy a tx19, or a bigger picklefork.
 

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I like to refer to her as my kneeboard with a big block Lol

I've been very suprised with the manners of it. I guess because it's so short, the deck doesn't wave at you at all going across the lake. Becuase I have no diverter, the worst manners it has, is it will porpoise up till about 40mph and then it settles down and rides okay. Been fun so far. Makes my girlfriend nervous though, she's used to bigger boats. She wants me to buy a tx19, or a bigger picklefork.
That's a good woman! Keep her LOL
 

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Discussion Starter #15
1st of all, I wanna say thanks to Tom at Jet Boat Performance for all of the help! When I need parts, I know where they will come from!

What I have...

Berkeley Intake
Tapered Shoe
American Turbine Pump
Center Blocker Loader

Shoe is 1/16" above keel
Loader is roughly 1.5" above keel
Pump is 4 degrees down
Ride plate is 4 degrees up
I have a 5 degree wedge installed
My nozzle is a 3.125"

Tom has suggested that I install an open loader level with keel and start there
 

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Dave , always good to talk , pictures help immensly , highly suggest that you drill and tap the suction to add some pressure guages so that vs strictly expirimentation that you actually have some readings to get a feels as to what the hardware changes do as you go forward Nice boat , has a lot of potential please be carefull ! Tom
 

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My son has a 17ft gullwing, three weeks ago he found out how fast things happen with that boat. He had just made a pass and was in a slow speed turn when a rough wave tossed the boat to the left. Catching him off guard he got off the gas and the motor died. As the wave rolled on through the right rear corner of the boat diped between the waves and got burried in the next wave rolling the boat on its top. this he said happened so fast that he and his passenger barely got out from under it. Neither was wearing a life jacket and by the grace of god neither was hurt. A few things to remember here. Any thing that boat does at high speed will happen fast, good, or bad. Never get to complacent it will bite you in the butt when you least expect it. Sounds like a retired race hull at 305lbs ruff water is not your friend, I would check that huill over throughly from transom to bow eye for stress cracks. And Always,,,,,Always wear a good life jacket.

If I sound like a nervous father :D Its because I am. At least my son wears a life jacket now with no exceptions.

Stay safe and have fun :)hand

PS find out some things about that type of hull from board members that have them and know them. They could save you some aches and pains.
 

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Discussion Starter #18
I've searched and searched as many boards as I could find for the same kind of boat. From what I understand, Mantra Boats was a very small operation.

Impatient1 on here has one, but he bought it not running and has been building a turbo LS1 deal for it, and has never driven it.

There used to be a guy in IL that owned one, and from what I understand, last year he caught a roller while racing and got ejected and busted the hull apart and it sank.


Tom, how do I setup the system for reading pressure on the pump? Is that something that is permanently installed in the boat, or temporarily rigged up?
 

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Tom, how do I setup the system for reading pressure on the pump? Is that something that is permanently installed in the boat, or temporarily rigged up?
I would drill and tap the suction , and run the lines thru small water tight bulkheads to pressure guages that are easily visable and permanently mounted , I've seen this done multiple ways (lots of good ideas here on PB) from simply using oil pressure guages to Marshall liquid fills the infomation will be of value to you when trying to get the setup right on your boat without data your having to depend on "seat of pants" feel to try to make adjustments and corrections ... Tom
 

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1st of all, I wanna say thanks to Tom at Jet Boat Performance for all of the help! When I need parts, I know where they will come from!

What I have...

Berkeley Intake
Tapered Shoe
American Turbine Pump
Center Blocker Loader

Shoe is 1/16" above keel
Loader is roughly 1.5" above keel
Pump is 4 degrees down
Ride plate is 4 degrees up
I have a 5 degree wedge installed
My nozzle is a 3.125"

Tom has suggested that I install an open loader level with keel and start there
from what you've said, at top speed water is breaking off the side of the boat about where the back seat would be? an open loader won't "help" that condition, and may make it worse. i wouldn't let what i would call an "open loader" anywhere near my boat.
you say the loader is 1.5" above keel? exactly which parts of the loader are 1.5" above the keel? the biting edges of the ramps?

you added a 5* wedge, raising nozzle angle? exactly what is the nozzle angle, compared to the keel (flat riding surface next to the shoe)? all hardware measurements should be relative to the angle of that flat spot next to the shoe.

when a boat is sunk so far at top speed that water is breaking off the side of the boat, the boat is said to be "too tight".
a boat that has no water breaking off the side, but both sponsons are in contact with the water, with a good attitude (nose height) of 3*-4* AT TOP SPEED, is desireable.
a boat that has the sponsons above the water line, riding on the center sponson or plate, is "too loose".
a boat that has the nose jacked up to the moon in an effort to "air the boat out" is a wreck looking for a place to happen.

"lift" is directly related to "too loose" or "too tight". the term is shortened from "keel lift". if the boat is "too tight", it needs more "lift". if it is "too loose", "lift" needs to be taken out of it.

the loader and shoe are used to fine tune the water feed to the pump. if you have the shoe shimmed too far down, suction pressure -may- be higher than desireable. that manifests itself when backing off the throttle, keel rises from too much pressure and the boat tries to bow steer. the loader affects suction pressure too, but it is much more difficult to "over pressure" the suction solely with a loader, than with a shoe. i like the loader ramps to be -about- the same depth as the shoe.

while it is important to obtain -adequate- suction pressure for TOP SPEED, generally with 500hp and the speed it will provide will not equate to a huge suction pressure value, in order to maintain bowl pressure.

keep in mind, anything you do to change suction pressure, such as a different loader, different shoe, different depths, etc., WILL have -some- effect on the looseness or tightness of the keel at TOP SPEED. it also has an effect on drag.

generally speaking. a light boat with a lot of horsepower would have a tapered shoe because the boat doesn't need additional lift at TOP SPEED, and will become too loose with a flat or backcut shoe. if you are running a tapered shoe, and the boat is too tight at TOP SPEED, that design shoe is not providing adequate keel lift.

there are two mechanical ways to increase lift. lower the thrust centerline, and/or use a backcut shoe. and just to deviate for a second. while we've already talked about suction pressure, a couple things about shoe measurements. the depth of the shoe should be noted as you did at 1/16 below keep centerline. ALL shoe measurements should be referenced to the "biting edge" of the shoe. in other words (an assumption on my part), when you say "the shoe is" we will interpret that to mean "the biting edge is"... secondly, once you know depth related to keel, remove the shoe and determine the exact depth of the biting edge from the mounting pad. could be 3/8", could be 5/8", could be somewhere else. it's important to know that and keep track of it. if you were to order another shoe, you would want the biting edge to be approximately in the same location as it was, and a backcut shoe will begin with a much thicker piece of material than a tapered shoe. whenever i change shoes, i shim to keep the biting edge in the same location as it was before. just related to shoe, suction pressure won't be any different if the biting edge is the same depth, regardless of whether or not it's backcut, tapered or flat.

with a stock berk intake set at 4* down, stock nozzle extension and fixed nozzle, nozzle angle would have been 4* down from keel angle. with a 5* wedge "up", you're now at 1*up from keel, and you've seen the result. at your power level, it would be good to try 3*-4* up just to see if the attitude will be good. also watch the boat to see if it's loose or tight at TOP SPEED with that much nozzle angle. you DO NOT WANT too much attitude (boat riding angle compared to water line) because on loss of power, that nose will drop rapidly. and the further it has to drop, the worse the potential result.

good luck and have fun with it.

p.s., if you get a wild hare and decide you want to jack the power way up, the setup will be completely different.
 
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