12" Setup Please Help!!!!! F1 Guys Or Drag Racers

[ALLISON7710]

INSTALLED A 12" OLDER STYLE CHAMP MID WITH WORM GEAR ADJ UP AND DOWN. NEED THE WING PLATES THAT WILL GIVE ME ENOUGH HEIGHT TO MEET EVEN WITH THE CABLES. THANKS FOR ANY HELP IN ADVANCE. ERIC.

[us1]

I sent you an email.

[ALLISON7710]

IT DID NOT COME THROUGH

[Raceman]

You'll probably have to make em unless Allison makes a set. The problem with the steering arms being offset above the pivot point of the tilt tube axis is that when trimming up the cables become slack. When I stuck the T4 on the 2001 I had a big problem with it and never really solved it satisfatorily. My old 16 Allison with the T3 suffered from the same problem, but with the Speedmaster and virtually no steering torque it wasn't a problem.

[ALLISON7710]

I WILL CALL BILL AT ALLISON TOMORROW. I MISSED THEM TODAY DUE TO THE TIME ZONE JUST THOUGHT SOMEONE MAY HAVE ONE OF THESE ANIMALS LAYING AROUND. WE ALREADY MACHINED BUSHINGS FOR MY ALLISON WING PLATES BUT ONLY TWO HOLES LINE UP BECAUSE THEY ARE OFF MY 15" MID. IT SHOULD WORK FINE BUT I DON'T LIKE THE IDEA OF IT.LOL THANKS ERIC.

[Raceman]

Eric, in a perfect world the steering bars would be easy to make. There are two pivot points to deal with, the tilt tube and the swivel pin. If the bars were designed to put the holes for the pulleys to hook up dead on plane with both of these points, there'd be no slack/tense points. Problem is boat clearance problems generally won't allow this and up down swivel brackets complicate it too, although only to a small extent with their short travel.

When I bought the Red & Yellow STV the cables would get real tight when making sharp turns to the point of binding. The bars, although made by a well known hardware builder were just plain wrong. It took changing the length to get them close to where the swivel pin was in a straight line between the two tips before it worked smoothly.

[ALLISON7710]

THANKS FOR YOUR HELP. I THINK I MAY HAVE FOUND A SET THAT WAS MADE FOR THAT MID AND WE WILL MODIFY THEM ACORDING TO MY STEERING. THANKS ERIC.

[Jeff_G]

Allison why the 12" center section? On a V bottom it creates too much back pressure and the hole shot is terrible. We are in the process of taking a 12" off and rebuilding the transom for a 15" on a Allison 15.

[ALLISON7710]

RUN IN PRO FUEL AT ODBA AND HOPE THAT THIS WILL MOVE THE CG FOWARD AND HELP THE HOLE SHOT NOT TO METION WHEN I AM NOT RUNNIN ODBA IT SHOULD WEIGH ABOUT 1175 WITH ME IN THE BOAT. LITE IS MITE AND LEAN IS MEAN. THANKS ERIC.

[steve]

I have a set of wings for you and the dimensions to make the angle you need to keep the cables from binding. On the 12" with the factory Merc wings , they get looser when you trim down rather then up like the 15" Allison wings do. You need the pivot point to be fairly close to where the steering tube ( trim pivot point) pivots to keep the tension approx the same at all trim angles. I like the sail boat pulleys better too. Call me, 815-626-6738--Steve

[Jeff_G]

Allison it will move the CG back not forward. You may have trouble clearing out the mid section so bad hot shot. Let us know.

[steve]

First off , all else being equal --setback etc. , a 12" vs a 15" will move the CG FORWARD not back. Picture--Removing weight from one end of a see saw . To balance the see saw you now move the center AWAY from the reduced weight not towards it. The 12" is about 40lbs lighter which means the boat pivot point will move forward and the rear of the boat will float higher ( very slightly) in the water unless you move ballast rearward. CG moves forward unless you add setback.

Next on the housing itself>>> there are several styles of 12" mids. The smaller 120 style WILL be more restrictive then the 2.4 style and it does add back pressure ( if stock) compared to the 15". But the 2.4 and 2.5 style really don't hurt the holeshot on a ProFuel or ProGas boat and the shorter mid combined with the boat launching better really improves the holeshot in that way as well as handling and top end because there is less weight on the transom and the boat runs flatter at topend. Running a 2.0 120 style downhousing is what Jaco's used to do and I have one of his setups. It still runs great and if the housing is relieved a bit and modded and runs the right tuner , it can run as well as any 15" SS . On the style that Eric has ( 2.4) , he needs to cut the housing above the bolt holes on the side and weld in a pc of "L" aluminum 1/4 " to make room for the longer S3000 tuner or G -force makes a good one too. It will be a marked IMPROVEMENT over the SS 15". Steve

[Raceman]

First of all, I don't think a G Force tuner is fit to take out of the box, let alone put on an engine. I've certainly never seen one help any engine that started off with a Merc high perf tuner, and have seen several break off. Just my opinion. As far as the CG comments go, the champ housings do have more offset than the standard V6 unit, I'm not sure if it's any more than a SS15 from Merc or not. I've got em all, but the SS's aren't within easy reach to go measure for comparison. In any case, I doubt that there's enough CG difference to make any real difference one way or the other. Certainly moving a battery around would offset any small difference between the two. The problem with the champ housings as Jeff Grigg correctly pointed out is that on a small V bottom like an Allison, the boat is so low in the water when off plane that virtually the hole tuner is jammed below the water line and regardless of the configuration of the outlet this can be a problem with hole shot, especially from real low speeds like the ODBA races start. This is not a result of anything but the shorter housing having the base of the powerhead approximately 3 inches closer to the waterline. When I first put a 2 liter motor with a champ housing on the 15 Allison it was tricky to get on top. The same housing with a T2X powerhead bolted on became almost impossible and we used to pull it off with a rope till the boat planed off. These of course were aggravated by running speedmasters with the props not slipping getting up as a over hub on a conventional gearcase would. The 2.4 powerhead on the same set up would jump right up without problems, but still under ODBA race conditions, I don't know how it would've done right off the start.

[steve]

I do agree about the tuner being swamped but the weight advantage pays off at the topend. Depends on how you relieve the downhousing I guess. I always like the launch with the 12". If you have the turned down snout , you need to cut it flush so it doesn't bucket water too.

The setback is about the same with the ALLISON 10" jackplate made for the Champ and the ALLISON 6" jackplate made for the SS . The steering tube is in a different spot and the distance from the tilt tube to the downhousing is a bunch shorter on the champ. The actual setbacks end up about the same. Really the advantage is the weight savings and where its sitting at . Any weight you can get off the rear of the transom on an Allison will make it run better. Thats been my experience. I agree also that Gene's early tuners cracked . But I think the swept back one he makes for F1 works pretty good. I personally run the S3000 and the "S" curved rect. one with some mods. I know Eric has the latter also.

[Rodney Nance]

The next time you go to a ODBA race watch the Pro Fuel class when they come into the starting lights. They may start out off plane and the tuner under water but when they get to the lights they are getting the tuner out of the water before the light comes on. Paul Freeman has almost had the big one a couple of times trying to get them to come in slow but those guy's aint buying what he's selling.

[Jeff_G]

Not knowing which mid section he has. The weight difference from most 15" to the champ is not that much. The champ mid is set back more that a stock mid. If it is the SS you can throw all this out the window! It is this setback that causes the CG to move back. The principal behind a fulcrum. If the setback for both mids are the same or the weight differential is more than the same setback then the CG could move forward but the difference would be almost impossible to measure. Kind of like scooting up one inch in your seat. The principals of a fulcrum are usually more pronounced than a slight weight difference.
How the boat runs is more a matter of weight distribution than just weight alone.

The only way to tell is to keep all the weight and balance just as they are and only do a mid swap. Then you are comparing apples to apples. There are so many other variables involved, setback, height, prop selection, tuner, etc.