IMCO Shorty and Extension Box Help
 

We are making some improvement to our boat and the next step is getting the IMCO shorty and extension box. I just want to make sure I do this correct the first time with the money we are about to spend.

This is going on a 26 Outlaw with a X-dimension of about 15.25". I want to get the most out of the outdrive without sacrificing handling or turning.

I am set on the 2" shorty and was told the IMCO neutral gives a 1" raise. But then I was told I can get a 3" extension box from IMCO as well. I went to their set and could not find one listed. Do they make one? What are some things I should consider and look out for? I don't want to make any mistakes.

Thanks for the help!
Rick

I do not have one but I have done a lot of research on it. I also raised my x dim last year by raising the engine and drive 3".
If you get the standard imco ext box it will actually lower your drive depth by almost 1" because of the angle of your transom.
You could get a 3" raised box and it will raise your propshaft depth by a little over 2". However your engine will have to be raised 3" and your exhaust will have to be adjusted.
The shorties come in -1 or -2 for a standard drive. Most guys with deep drive Baja's have good luck with these.
I am going by memory on this but my it seems my x was 14 1/4" and I raised it to 17 1/4". That equates to a propshaft depth of 8" to 5". With the drive being set back 12" you should be able to run 3" to 4" deep.
Your oudrive should be about 7" deep right now. I have measured a few 25 outlaws and some of the later models were raised to 6.5" at the factory.

If you get a 3" raise Imco box, you also have to raise the engine 3".
I would just try the -2 shorty first without the box.

You most likely do not want your propshaft depth any higher than about 4.5-5". All that will happen is you will get more propslip and less bowlift.

Search Wildcard's posts. Shorty by itself doesn't do much of anything. Extension box works great with good horsepower. WIldcard did the 3" extension box and standard lower. It worked great. He tried a 2" shorty for a total of 5" and it was too much. So, extension box is key. 2"-3" seems to be the magic number.

I would do the neutral box and your 2" shorty to avoid the headache of raising the motor.

What power do you have. If it's stock 496 or 496ho I don't know if you will see anything. Wild card put a 525efi in when he did the box. and then later switched to a 600sci. 500+hp and the gains become very noticeable.

Hey Griff, you always give good advice but I have a 24' Baja with a drive 5" deep. I use a Mirage 25p prop with a lab finnish and double cup. I only have 9.8% slip at 74 MPH. I would think you could go a little higher with the 12" setback. Especially if you used a 4 blade prop.

Guys... thank you for the great replies! :coolcowboy:

I was not aware that the engine also needed to be raised as well... that is not going to be an option.

We are going to have well over 500HP when the engine is all done. So the Neutral Box and 2" Shorty will be the way we go.

Griff, a prop shaft depth of 4.5"-5" is a good target? I want to understand why is this? Because, I have some people telling me I want the shaft level with the keel. This would seem very extreme to me. I want to get the most out the boat but I do not want to sacrifice the basic handling abilities.

Thanks again everyone for taking the time to help! :drink:



jeffswav, do you boat on the Kaskaskia River? If so, we'll have to meet up one day for a run.

Yea, you have a 26 Outlaw. Does it have red a black graphics? We go there quite a bit, its only 30min from my house. We go to Kinkaid a couple times and take a big trip to Norfork once a year. I think we are going to try Rend lake this year also.

If you aim for the p/s level w/bottom.

1. You'll never get it on plane ( unless you use a 6 blade prop)

2. If you somehow were able to get it on plane, you
wouldnt have any trim leverage ( which you need
on a regular V hull)

I tried a set of 2" shorties on my boat ( which the drive
height is 3" below the bottom of the boat) and could
not get it on plane (and that was with 5 blades, and boxes)

You could do a Stellings box and raise the drive up without moving the engine. You can set it at 0, +1 or +2, you would have a drive shaft with u-joints instead of the shaft with coupler. I think that is what Griff uses.

That was us, the red and black 26 was our old one.

We certainly boat on the same bodies of water. We love Norfork and enjoy a trip or two to Kinkaid.

JaayTeee, thanks for the good information!

I am going to go with the neutral and 2" shorty like I had originally planned on doing.

Thats really only going to raise you up 1". You could go much higher than that, that will be real expensive and not a lot of speed gain, maybe 2 MPH. Just doing the shortie without the box will get you 2-3 MPH. With what you have I would take a closer look at the stellings and keep your current lower. Unless you want to raise your engine up 3" and do the raised imco box.

:picard1:

So much information and misinformation (not saying your is misinformation :drink:) since I started this project. I am starting to get very nervous now that I'm into this project.... the last thing I want to do is spend thousands for minimal gains if any at all. :picard1:

I have a call into Stellings and I will see what they say.

The one thing I want to do for sure is get the E-box on now before the engine goes back in.

The more research you do the better. I know how to go fast, you know that, if my budget were bigger we would really be in trouble. :eek:

I was refering to 4.5-5" without the ext box. He could go up about another inch with with a neutral box.
The longer the boat, the harder it will be to carry the bow. When you compare LOA, a 26 Outlaw is about 4' longer than your 236. With a swim platform, he is about 27.5'
As an example. my 28 Pantera was set at about 3.75" and it wasn't deep enough. Propslip was over 22%. I had to go down another inch. The 1" decreased slip to about 17%, improved the ride, cruise speed and increased top end by 1-2mph. This was all with a Bravo 1 4 blade.

Yes, I have Stelling Boxes and they are adjustable, but mine were set as high as they could go from the factory.
You do have to be careful with the amount of angle when you raise the Stellings boxes. Too much angle will stress the U joints. My engines are moved forward with a driveshaft, so my angle is greatly reduced.

25' outlaw and 26 outlaw are nearly identical. WildCard09's numbers (25' outlaw) are on OSO. WC09's best was 3" raised, but it was the box (combined with good horsepower) that made the big difference. Neutral box and 2" shorty will be great for you. I think you'll gain 2-3 minimum. could be as much as 4-5. FYI- 2" shorty by itself doesn't do much of anything on a 26 outlaw but look cool as hell. - I've tried it myself.

Your plan is a good one. Roll with it and keep us posted.

I had the same plan, but burned out trying props etc. and lost motivation after the shorty by itself -dealing with water pressure issues setting my guardian off. So decided to leave mine as is for now. I've got a 600sci so have pretty good speed to begin with. If I ever start messing with it again, I will go straight to the box.

Griff, I agree, without a box 4.5 to 5" should be your target. But if he adds the box he should go up higher, more like 3".

I've never heard of any ext. box lowering the "X" Sorry to jump in so late in the game. Even the neutral (so called) boxes are made on the slant, compensating for transom angle. I've never seen a straight box that would push the "X" down. I have Stellings boxes and in the neutral position theres a slight raise and adjustable up to 3" raise. I chose Stellings because it uses a shaft and "U" joints to connect to the engine and raising the engines wasn't required. Since I also pushed the engines forward 2' I used drive line bellhousings and trans replacers so I was able to retain the Bravo rubber couplers and save some shock to my drives.

The reason guys say extension boxes lower the x is because, in theory they do. As the water leaves the bottom of the boat it rises up. When you move the propeller away from the boat it meets the water at a higher level than it would if it were closer to the boat. Savy?
My 29 is at 4.25" and is about all the higher I would want to go on MY boat. Each boat is different and therefore will react differently to a box.
IMCO may still have a +3 box or 2 laying around, but last I checked they were not producing them anymore. Call & ask.
As far as actually choosing the best option, chose the option with the most versatility. A Stellings box with a -2" lower would give you the most to chose from with adjustments. Up/down on the box + the ability to space the -2" lower down. ALWAYS buy the shortest lower you can. Spacers are cheaper than cases.
I wouldn't want to fo what Wildcard did to his boat. I think that is too much & it took away from the overall performance of the boat. I know it was/is fast, but there is a very distinct line between fast & quick. I'd rather have quick. You'll keep the handling of the boat & you'll be less hard on the drive because it won't be getting aired out as often when it's deeper in the water.

If this were my project, I'd do a neutral IMCO box with a -3" drive from IMCO. The -3" IMCO is a complete drive, although people have altered their Bravos cavitation plate to accept the -3" lower. You can still space it down if needed.
I run the -3" IMCO SC Extreme. It is a decent drive with XR internals.
Check the classifieds, they are in there quite often.
Whatever you do, just remember you don't want the X up too high. I think I'd shoot for the 4.25-5" range like others have suggested.
You certainly don't want to loose too much leverage by going too short.

Thanks for the additional information.

I was told with the -3 lower I couldn't run a big prop (which is an entirely different can of worms). I am waiting to see what the final HP will be once everything is put back together before I start thinking about props. What prop sizes will be limited on the -3?

Beats me on prop sizes. I ran P5X's and Maximus wheels and never had a clearance issue.

So what is the limiting factor with the -3?

You can only run the -3 shortie on a Imco drive.

You can run it on a regular Bravo upper, but you have to cut the cavitation plate.

OH!! Gotcha! I remember reading that in another thread now.

Thanks

TW720HVY, this will answer your questions on actual height with a box.

Rumors of the X being lowered 1" was based on using a straight box or a transom angle other than 13 degrees. not from the water rising as it leaves the transom.

Here is why:
Bravo transom assemblies are based on a 13 degree transom angle (middle of what is required). But all boats are different and vary. Mercruiser installation requirements say the transom angle must be between 10 and 16 degrees. When the Bravo transom assembly is mounted to a 13 degree transom angle, the bell housing where the drive mounts, will be straight or at 0 degrees. The best way to picture it being at 0 degrees is to imagine this: Instead of the shaft coming out of the drive having u-joints, imagine it being straight with no u-joints. Assuming it was straight with the drive bolted to the bell housing, the prop shaft will be parallel with both the engine crankshaft centerline and the bottom of the boat.

So if you put a straight box 12" long on a 13 degree transom angle, the transom assembly will be exactly 1" lower than if it was bolted to the transom without a box. Both stellings and the Imco boxes are at a 13 degree angle. This is why the Imco neutral box can use a straight drive shaft. If the box were at an angle other than 13 degrees, the straight shaft would not plug into the engine coupler. It is also the reason the Imco 3" raised box requires you to raise the engine. If you did not raise the engine, the shaft would try to plug into the coupler 3 inches higher.

The Stellings in the nuetral position and the Imco Neutral box mounted to a 13 degree transom will place the X at the exact same height that it was without the box. Except that it is 12" back.

As mentioned earlier...sometimes the X with a neutral box may be a little higher or lower. If the transom angle is greater than 13 degrees, it will lower the X. With an angle less than 13 degrees it will raise the X.

To imagine what I mean by the box being at a 13 degree angle and to get an idea of how the X can change with different transom angles...draw a line on a piece of paper a few inches long on a 13 degree angle, draw the same line offset a few inches and connect them with 2 paralle lines. It should look like this:

. ____
/____/

I built my own boxes similiar to the Stelling (uses a drive shaft) about 7 years ago. So I spent a bit of time playing with this in CAD prior to building my boxes.

I would say the box with the -2 would be about as radical as I would go. You get to high and its hard to hook up out of the hole. The higher you go handling and truning will definitely suffer. You are going with a hyd. steering system right?

Todd... thank you for the fantastic information. What you said makes perfect sense. I will try and find out what my transom angle is.

I already have the Latham Marine full hydraulic system. I need to check with them to see if there are any limitations with IMCO wing plate. Also, I will have to figure out how long the lines will need to be.

My X-dimension is 15.5".... does anyone the exact distance from the center of the drive shaft to the center line of the prop shaft of the Bravo 1 X-Drive?

Are you sure its not 15.25? I think that would put you at 7" deep. The late model 25's were 6.5" deep, that would be strange if they went deeper on the 26. There is a guy that hangs out in the Baja section, xt inivator he worked at the Baja factory. Send him a pm and see what he thinks they were set at.

This is a Baja by Fountain and the X-dim is right off the performance report. The earlier Baja by Fountain boats had higher X-dim but for some reason on ours they went back to or close to the Baja by Brunswick X-dim.

I will post the transom question in the Baja section, hopefully someone there knows the answer.

Thanks again for all the help!

Take a look at this post. http://www.offshoreonly.com/forums/b...25-outlaw.html It looks like he had the best rusults at 3.5" depth.
Here is a post I started a while back http://www.offshoreonly.com/forums/d...ive-depth.html

Jeff... thanks for the links!! :drink:

With the box, he should go about 1" higher, or maybe 1.5".

I would go with the -3 lower like Jason said and have a 1/2 inch spacer ready.

Rick, it was great talking with you the other day. Now we can keep track on facebook also.
If it were me, I would drop the engine in and run it this season. There is a lot of rigging to change over and it's almost April. Get some numbers after doing the engine upgrades and think about the box and drive next winter. I have some ideas we can talk about when tied up at the river. If you get 575 HP out of the engine you should be in the low 70's without any drive adjustments. Besides it you do everything this year your boat might be faster than mine. That will really screw things up for me. :lolhit:

Sorry, I never noticed the question before...the distance is
21-13/16.

Todd... thanks for the great information! No need to apologize. :drink:

my baja24 ol loved the 2'' shortie and wildcards 25ol did the 3'' raised box plus settled with 1'' shortie is what his ended up being. so at 3 1/2'' to 4'' on the 25ol. the 26 should be fine with that same set up. my friends 31 sutphen single has a propshaft height of 3 3/8'' with no box he is running 90 plus. my new 28 has a 3 1/2'' height so we will see this summer how it runs plus I have a konrad ace set up.

last pm I had with him he put a 1'' spacer in the 2'' shortie= total of 4'' he was at 87 or 89 with the 600 merc. he went from 74 to 81 with the 525 I did a 2'' shortie and added a bigger carb and with the same prop I picked up 8mph and never got to try a bigger prop plus my boat and wildcards flew more level across the rough water.going with a n box= the same as 1'' lower. every 12'' back = 1'' down.

save your money just get the 2'' shortie, like I just posted 12'' back = the same as 1'' lower.