Eliminator Scorpion running flat and wet

[502 JET]

I have an 86 Eliminator Scorpion. The boat drags its a$$ and runs flat and wet. After searching I found that this is an issue with with these hulls, and that's why the were only made for a few years. I also seen it mentioned they were better suited with an outboard and don't work very well as a jet. Well I'm stuck with the boat for now. Its stable and a nice ride but wont set the world on fire.
Is there anything that I can do to get more lift to get the hull on top of the water?
I would like to know what is so different about the bottom on this boat compared to the better performing tunnel hulls as I understand this is what is holding the boat back.
Anyone have bottom photos of the better performing/more desirable tunnel hulls or know where I could find some? I'd like to compare them to my hull.
My boat has a shoe and ride plate. The shoe is tapered. In the pic the shoe is 1/8" above the keel. The ride plate has some up angle to it. I have not put an angle finder on it yet so I don't know the degrees of angle. The pump has a loader, which I sharpened all the leading edges. The loaders leading edge hangs about an inch below the keel. The pump is fresh with a stock AA American Turbine stainless impeller, clearance @ 25 thousandths. I also spent a lot of time blending the suction housing to the intake housing removing all sharp edges, filling low spots and speed coating the inside of the pump. The bottom of the boat is flat and smooth, it is a perfect transition to the intake. Also running a diverter and droop.
At 6000 rpm it feels like the boat noses over and the rpms go up. Could this be cavitation at this point? I have gpsed @ 85 mph with two people, full interior, 30 gals. of gas and the tool bag on board. I don't know the hull weight. Its not a light layup.
Sorry about the large photo its the only one I have of the boat at speed.
http://www.hotboatpics.com/pics/data/500/15596DSC00837.JPG

[MADDOG355]

At 6000 rpm it feels like the boat noses over and the rpms go up. Could this be cavitation at this point?
I would think so.
What loader do you have?
You did not say if you had a droop or place diverter, I would recomend both.
From the pic I see 2 cables so I assume it has a place diverter, Most seem to run best with around a 3-6 foot tail (that is just a rough guess you will have to find what works best for you). In the pic it looks like the diverter is down to low in my opinion.

[502 JET]

I forgot to mention it has a diverter and a droop. I have tried different settings on the diverter, didn't make much of a difference other than making the boat loose when rasing the tail.
My loader is similar in design to this one. With the exception being my ramps are longer covering up two of the mounting bolts.http://www.hotboatpics.com/pics/data/500/15596c51b_1.jpg

[Squirtin Thunder]

Sometimes a little down wedge will help as well as a Jack Mc Clure custom loader.

[MADDOG355]

They make a few different ones, I would be afraid to make a sugustion on loaders (I don't have any experince with tunnels).
I am thinking th ride plate could be part of the problem if it is not set right.
I am shure some of the tunnel gurus will post and give you some more ideas.

[Rondane]

I would like to know what is so different about the bottom on this boat compared to the better performing tunnel hulls as I understand this is what is holding the boat back.
That boat was made wider with less sponson in the front unlike a daytona which does not enable it to take a good set. It does exactly what your describing. A good wave will come right over that nose from what i understand if your not careful. Not sure about the bottom. Is that a flat keel or round? If it's a flat one you need to put that shoe level with keel to start. my .02
rondane

[MAXIMUS]

check your pm's...

[sdpm]

I worked with a guy years ago on this same hull with the same problem. The only way that we could make it run was by dropping the shoe below the keel and it had to be a flat shoe (no taper or backcut). The center pod of the boat has a bad design and without changing it this was the only way it would work. It would tend to spray water back up over the bow and would not turn at all. I did not like doing this but it was what had to be done. Be very careful. With the shoe this deep, the boat can be very dangerous if shut down to quick or looses power. I don't advise it!

[JR131]

give HB from R&D marine a call we ran 2 of these boats and held records
with them or go to the web site r-dmarine.com and check out the picts
we had a boat that was almost identical to that. when set up right that boat is about a half of a second quicker than a daytona
(714)993-2664 ask for Harold
jr
http://www.r-dmarine.com/files/Download/jrmod.jpg

[JR131]

http://i206.photobucket.com/albums/bb281/greeley_b3/rookie.jpg:idea:

[502 JET]

I worked with a guy years ago on this same hull with the same problem. The only way that we could make it run was by dropping the shoe below the keel and it had to be a flat shoe (no taper or backcut). The center pod of the boat has a bad design and without changing it this was the only way it would work. It would tend to spray water back up over the bow and would not turn at all. I did not like doing this but it was what had to be done. Be very careful. With the shoe this deep, the boat can be very dangerous if shut down to quick or looses power. I don't advise it!
I search the archives here and found some info that dropping the shoe may help so I made a shim and lowered the shoe .030" below the keel last night. It was 1/8" above the keel before. I'm gonna run the boat today and see if it changes anything. Starting off slowly of course. Thanks for the advice.

[502 JET]

That boat was made wider with less sponson in the front unlike a daytona which does not enable it to take a good set. It does exactly what your describing. A good wave will come right over that nose from what i understand if your not careful. Not sure about the bottom. Is that a flat keel or round? If it's a flat one you need to put that shoe level with keel to start. my .02
rondane
I have rolled a few wakes over the nose, not going fast but crossing wakes too slow with the bow down.
The center of the keel is slightly rounded and flat on the sides of it. I'll try and snap some pics of the bottom today. I dropped the shoe and will test it today.

[502 JET]

Thanks JR this is the first positive thing I've seen or heard about this hull. This looks like my boat I just gotta get mine to take set like that.
My boat had the name "Diamond JIM" on it at one time in its life. It was on the side of the cockpit next to the driver.
http://www.r-dmarine.com/files/Download/jrmod.jpg

[thatguy]

Rodane, where is your boat?

[JR131]

yea i wish we still had ours that boat was alot of fun like
i said just give him a call and he will help in any way he can
have fun
jr

[DUCKY]

You definitely can't argue with the performance numbers on the boats above. But there is one thing I notice about both of those pics. The nose is up, but both boats are still dragging the tail in a sense, because the rear most corners are still touching the surface of the water. Basically what is happening in both pics is the boat is setup to fly the nose, and you are relying on the corners of the sponsons to hold in enough air to keep the tail up. With the research I have done of these hulls, I have found two major problems that hold true from the Scorpion, to the Banshee, and beyond. In an outboard application, the hull does not have sufficient surface area to carry the weight of a motor hanging 6-10" behind the boat. In a jet application, since the weight is much more evenly distributed, the surface area isn't the problem, it's just the lack of natural tail lift (which is generally overcome with power) compounded by the fact the the tunnels not only have no compression in them, their corners actually open up and cause the tunnel to get looser towards the rear of the boat.
In 502's case, I make the following suggestions. First off, if the boat has tunnel tabs (many did), they need to come down quite a bit. Now I know that many of you jet guys are going to have a field day with that comment, but what needs to be remembered is that tunnel tabs are not ride plates. Their function is to control the amount of air being dumped from the tunnel. If you do have tabs, you may also consider attaching some aluminum angle to the sides of the tabs to create "dams" to prevent some of the air from releasing too early. After you have gotten some compression in the tunnels, then it's time to get the nose up some, which you should be able to accomplish with ride plate and shoe changes. I think the flat shoe at keel depth will be the place to start. Do you have a wedge in the pump now? Where is your ride plate set?
Regardless of what you do (short of extensive bottom mods) the boat is going to run flatter than most, especially at low speed. That has been the demise of many of these hulls. But flat isn't the problem, it's the low and wet part. Look at a Mirage or STV outboard...They run at about a 2-3 degree angle of attack, with virtually no hull in the water.
PS, to Rondane, these hulls are much narrower than a Daytona, especially up front.

[Sleeper CP]

Thanks JR this is the first positive thing I've seen or heard about this hull. This looks like my boat I just gotta get mine to take set like that.
My boat had the name "Diamond JIM" on it at one time in its life. It was on the side of the cockpit next to the driver.
http://www.r-dmarine.com/files/Download/jrmod.jpg
Is that Ron Signi in the lane next to you in his old '"Blue Bomber" CP Gullwing.
Sleeper CP

[502 JET]

I don't have tunnel tabs. So for now those options are out.
I'm not running a wedge and need to get an angle gauge to measure the ride plate. The ride plate is angling up, I don't know how many degrees.
The bottom mods are not out of the question if that's what it needs I'll do it.
What about a wider ride plate? Would this help pull the transom up on top of the water?

[JR131]

yes it is Ron
the reason you can run so much nose lift is because it has so much
positive down force on the deck but we also changed the keel quite a bit from the standard bottom to get it out of the water like that
jr

[Squirtin Thunder]

Down wedge will lower your thrust line and in turn lift the whole boat some. If you have a 4* intake and no + or - wedge and a droop you are @ 3* up this also helps creat bow lift. But if you want transom lift a 3* down wedge is the place to start, and the cheepest.

[JR131]

yes that is true but that will also force the water to come over the deck during shut down

[sdpm]

yes it is Ron
the reason you can run so much nose lift is because it has so much
positive down force on the deck but we also changed the keel quite a bit from the standard bottom to get it out of the water like that
jr
Hi Jr, I think your dad was about the only one that could make these boats work. I remember him running one back in the mid 80's at Parker and he was the only one and had it working real well. I just never did like how high the nose was on them! Neil

[JR131]

yea i think you are right
the only way to make these hulls well is to do the bottom
jr

[502 JET]

yes it is Ron
the reason you can run so much nose lift is because it has so much
positive down force on the deck but we also changed the keel quite a bit from the standard bottom to get it out of the water like that
jr
Do you have any pics of the modified bottom?
I've seen terms used like dropped keel and spoon. Is this somthing that was done to your boats?

[JR131]

no picts sorry
but like i said just give hb a call and he will help you out
jr

[502 JET]

no picts sorry
but like i said just give hb a call and he will help you out
jr
Thankyou.....I called and left a message for him

[Liberator TJ1984]

All I know is Greg / Underdog630 here on the boards had one , it also ran very flat and wet . and from what others are telling you about being careful ... I'd listen to them , His would swap the tail in a heartbeat ! he sold it to another guy and he proceeded to throw his family out and damn near sink with alot less motor than what Greg was running and he was not going very fast either.

[JR131]

thats true when you try to push the boat over on the nose to run them high and flat this is why you need to change the keel angle that boat wasn't built to be jet friendly without the changes
jr

[565edge]

I had a advantage banshee(same boat). I had papp do a bunch of work to it. It was a very very wet ride.Alot of people just put a very deep shoe in them..Ive seen some that where over a 1" thick.Mine had a built 500" chevy and never ran worth a crap. Harold is the only one to make these boats work. I talked with him several times about mine at the races and was going to have him do the bottom but bought a 19' stealth instead..I do love the looks of those boats...Good luck...

[502 JET]

I didn't get the boat out today. I got busy and ran out of daylight. So I'm shooting for tomorrow morning.
I'd like to say thanks again JR. and thankyou to the others for suggestions.
I spoke with Harold Bruce from R&D Marine (http://r-dmarine.com/default.htm). It was very nice of him to take the time and call me back and share his secrets and talents with me. He said to go ahead and play around with setup changes but to get the most gain I will have to modify the bottom. He explained in detail how and what to do to the bottom to get the boat up on top of the water. He even offered to help out along the way when I do the bottom.
When the seasons is over I 'm going to do the bottom as suggested, for now I'll tinker around with the hardware and enjoy the rest of the summer.
All I know is Greg / Underdog630 here on the boards had one , it also ran very flat and wet . and from what others are telling you about being careful ... I'd listen to them , His would swap the tail in a heartbeat ! he sold it to another guy and he proceeded to throw his family out and damn near sink with a lot less motor than what Greg was running and he was not going very fast either.
Could you explain swap the tail.:confused: Spin out?
My boat so far rides smooth and uneventful. It's also very stable on shutdown. It's never done anything unpredictable.

[jdf]

http://i206.photobucket.com/albums/bb281/greeley_b3/rookie.jpg:idea:
hey we own this ride now

[hotbo]

I didn't get the boat out today. I got busy and ran out of daylight. So I'm shooting for tomorrow morning.
I'd like to say thanks again JR. and thankyou to the others for suggestions.
I spoke with Harold Bruce from R&D Marine (http://r-dmarine.com/default.htm). It was very nice of him to take the time and call me back and share his secrets and talents with me. He said to go ahead and play around with setup changes but to get the most gain I will have to modify the bottom. He explained in detail how and what to do to the bottom to get the boat up on top of the water. He even offered to help out along the way when I do the bottom.
When the seasons is over I 'm going to do the bottom as suggested, for now I'll tinker around with the hardware and enjoy the rest of the summer.
Could you explain swap the tail.:confused: Spin out?
My boat so far rides smooth and uneventful. It's also very stable on shutdown. It's never done anything unpredictable.
when you start drooping that shoe below keel sometimes and most times it will cuase hairy shutdowns.the boat can nose dive really bad if let off to sudden,can tail walk,or porpiose you never know just be careful and play slowly at first cause the boat will set different and act different.:D

[502 JET]

hey we own this ride now
How's it running? Is the bottom work holding up after all these years? Do you have any pics of the bottom?
When you start drooping that shoe below keel sometimes and most times it will cause hairy shutdown's boat can nose dive really bad if let off to sudden, can tail walk, or porpoise you never know just be careful and play slowly at first cause the boat will set different and act different.:D
Thanks for the advice.
I'll start off slowly and see how it reacts to the changes, I sure as he!! don't want to get pitched out.
I'm off to the river.

[Liberator TJ1984]

502Jet ,
spinning out is what his would do , for some reason while turning ! it would unhook at the rear ? bad part is You just never could tell when or why. I would almost describe it like hooking a sponson on a roller and having it whip the ass end around ? except water was smooth...
But just as the others stated , when he called around almost everyone told him his hull was designed for an outboard , and did not like the jet drive setup.
I personnally never rode with him , but was there twice when it pulled its swapparoo trick . thankfully he was not going more than about 30 mph when it would do it and never pitched him completely out of the boat. Who knows someone may have tinkered with it before him and really screwed up his hull bottom ??

[502 JET]

502Jet ,
spinning out is what his would do , for some reason while turning ! it would unhook at the rear ? bad part is You just never could tell when or why. I would almost describe it like hooking a sponson on a roller and having it whip the ass end around ? except water was smooth...
But just as the others stated , when he called around almost everyone told him his hull was designed for an outboard , and did not like the jet drive setup.
I personnally never rode with him , but was there twice when it pulled its swapparoo trick . thankfully he was not going more than about 30 mph when it would do it and never pitched him completely out of the boat. Who knows someone may have tinkered with it before him and really screwed up his hull bottom ??
I never tried turning my boat fast. It don't handle like a sprint boat that's for sure. I always slow down and turn around. If I let off the gas and turned the wheel then nailed the gas again it may spin out. But that's not something I would try with a boat. I have done it on a jetski though. :D

[502 JET]

I went to the river today but couldn't gps the boat, too much traffic.:mad: The boat still shuts down smoothly after dropping the shoe. There's no telling if I hurt or gained performance until I can get some clean water and run the gps.
The leading edges of the ramps on my loader hang 1" below the keel. Does this sound correct?:confused:
It seems to me that this would cause a huge drag and help pull the bow down.

[jdf]

like jr said it like's to fly the nose ....it still has the same hardware and setup on the pump when jr and sr had it ....we are putting a 496 with a 250 shot in it

[SD Beach]

Well 502 you will have a fun boat once you set it up correct. They are great boats, but need some work to get there.
I would go to the person that knows how to make them run (R&D)
Educated guess can be ok but some time dangerous. He has made them run.
Don't put the shoe below the bottom of the boat (dangerous)
Keep us updated on the progress.....
A Scorpion is wider then a Daytona

[hotbo]

I went to the river today but couldn't gps the boat, too much traffic.:mad: The boat still shuts down smoothly after dropping the shoe. There's no telling if I hurt or gained performance until I can get some clean water and run the gps.
The leading edges of the ramps on my loader hang 1" below the keel. Does this sound correct?:confused:
It seems to me that this would cause a huge drag and help pull the bow down.
i have never heard of a loader being that far below keel,:idea: huge drag i would think also.imo you need to cut that back some cut back alittle at a time and retest to see if it helps.imo the loader being that far below keel its blocking the shoe some and not letting that front of the boat pick up some.but then again im just a amature and these are only my opinons but i do wish you luck and hope something i said helps.:D

[JR131]

cut the ramps back so they start just past the second bolt hole on the pad
this should get you above the bottom
jr