Anyone using a IMCO shortened lower units.

[Richard Rees]

I have a 22 classic 454 mag efi. and i am thing about a 2" SHORTEY, would like any pros or cons about using one? thanks richard

[RedDog]

I have only heard positives about this. Do a search on this board and you'll find a lot of info.

wish I had one...

[roadtrip se]

I've had one for two seasons and really like it.

Lots of pros and cons.

RD is right, do a search here, read up, and then if you would like to chat about my experiences, PM me your numbers.

Always happy to help a guy out from Texas!

Todd from the tundra!

[gcarter]

Catch 22 (Jim Collins) installed one and it was good for three MPH on a cool day, on a warm day, no improvement.
But when he got the Procharger.......he picked up about 18 MPH!!
I believe the shorty is a big part of that increase, i.e. the boat was better able to utilize the extra HP.

[roadtrip se]

Let's do some math here...

The shortie is good for 3-5 mph, Fred Inman will tell you that at IMCO.

A stock 454mag turns 385hp. Procharged, it is probably in the 600+ish range or an increase of 215hp. Common swag for each 1 mph increase, you need 15hp give or take. A 215hp increase divides out to an 14+mph increase.

So an 18mph increase is reality when you add the two together, but help me understand the physics of the shorty taking advantage of the horsepower?

They are really separate upgrades and a 454mag will see an increase without a massive engine change.

I was running a 502mag at 415 hp. I installed the 500hp at "470hp", which is more like 500hp as under-rated by Mercury racing. A 85Hp gain or 5+mph, plus the 3-5mph from the shortie, equals 8-10mph. I ran 70-72 with the 502, I run a little over 80 on a good day today.

Here is the kicker...

After running neck and neck with Dr. Dan's "stock" 500 cobra drive combo at 1000 islands, I question the real world benefit of a shortie drive if all you are looking for is top end increases.
Our boats run pretty close to even... so there goes that theory... Dan may not be stock, but he isn't turning 75 more horsepower than I am to make up for the Cobra drive.

The speed increase, the ability to turn bigger props, and the bling, bling factor are cool. But there are also the additional expenses of steering, slower time to plane, and handling changes that some people may or may not like.

Never know until you try it!

Todd

[gcarter]

I've always felt that when your running less than 10% (+/-) slip, the intangables become monumental.
I've been following Jim and his boat for about a year. On my first ride, he was doing 71-72 GPS with four on board in light chop with Bravo I, double ram hydraulic steering (I don't remember what brand), and a 23P prop (again I don't remember what particulars).
After installing the shorty, on a particularly cool day in August(I think) he increased 3MPH. On any given warmer day, there was no measurable increase in speed i.e. you needed some additional power to appreciate any increase in speed over a stock Bravo. This seems to indicate there is a power "threshold" in those conditions where the reduced parasite drag made a difference. This, of course, is about as un-scientific as you can get.
When the Procharger was installed, he immediately went to 89 MPH GPS with a prop change (27" I think), and of course, again, this was on a cool day.
I'm just philosophising here, but it would seem the lower parasite drag of the shorty would be a bigger part of the equation at 90 MPH than 70 MPH.
Then again, I may have no idea of what I'm talking about.

[Rootsy]

89 with a 27P???? what the heck does he have for a gear ratio or just how many rpm is that motor turning????

i spin a 27, 5100 - 5200 rpm with a 1.47:1... 79 - 81ish... with the alpha SS

JR

[gcarter]

Max RPM's are 5500. :smash:

[Richard Rees]

Thanks for all the helpful info. thanks again.

[catch 22]

Heres what's going on...when the motor was stock 454mag mpi with a bravo 1 1.5 gear ratio the boat ran 68-69mph with a 23p mirage plus. After changing the exhaust to stainless marine and a few weeks later changing the lower to the imco 2 inch shortie I Didn't have a whole lot of testing between mods, so I really don't know what gave me the extra 3mph gain. I was at Mt. Dora last March and took George (G-Carter) for a ride with my wife and dad and the boat ran 71-72mph all day. Hydro q4 23p. After that weekend the boat never ran that fast again 70mph was max. After tearing it down we saw that it had a bad fuel regulator. Now with the Pro-Charger M3 and a 504 intercooler the boat ran 89mph gps right out of the box with a 27 mirage plus at 5500rpm. I had a problem after that first time out that the boat did not want to run when it built boost. Found out that it had a bad distributor cap and I had the fuel tank flushed and filtered and the injectors cleaned. I took the boat out again with the same 27p mirage plus and it was all over the limiter. Tried a 27p hydro q4 and it was also on the limiter hard @ 78mph. Tried a 29p mirage plus and went 88mph @ 5600-5700 touching the limiter. Then I tried a 28p Bravo 1 and went 85mph @ 5600-5700rpm. Going to try a 30p Bravo 1 this weekend to try and get the rpm's down. I don't know why the boat ran so good with the 27 mirage plus and after the little tune up it's turning these others to high. :confused:

[catch 22]

MORE INPUT......NEED MORE INPUT. :wavey:

[gcarter]

So Jim and Jena Collins (Catch 22) came up from Palm Beach County to test some props on Lake Harris.
I dropped by the Leesburg Marina to observe while taking a break from working on the Minx.
First up was a labbed 30P Bravo, the results were 89 MPH @ 5600 RPMs.....not the direction they wanted to go.
Next was a new 32P Bravo....86 MPH @ 5100 RPM. This was better on engine speed. I think the final concensus was more testing needs to be done and maybe a different brand of prop needs to be tried.
I suppose the photos will be frustrating to those of you digging out of a snow bank! :splat:
Sorry......

:wavey:

P.S. The two folks in the second pic is Jim on the left and his dad on the right. Other than their height they look just alike.

[catch 22]

Ok Scott, I get it. :biggrin.: On the way home from my folks I called Throttle Up and spoke to Matt, He suggested that I try a 4 and a 5 blade HYDRO . I have a 5 blade 30p lined up for this Saturday and I am going to have Matt send me a 4 blade. Will keep you posted as to what happens next. P.S. George you should have went for a ride it was nice out there. :biggrin.: :biggrin.: Had a great time at R.J. Gators. :wavey:

[DonCig]

Today was the day to start the AOTH Rocky Mountain Skunkworks projects. I received my -2" Satin Imco Shorty and had time today to mount it on the Bravo 1 outdrive. Rough measurements have the centerline of the propshaft at 4" to 6" below the bottom of the keel. I need to back the boat off the trailer a little bit to get a perfect measurement.
I have a list of 6 things to get done before AOTH.
1. Imco -2" Shorty (Done)
2. Livorsi GPS Speedo (In Process)
3. GLM Exhaust Manifolds (Pending)
4. San Juan Fresh Water Cooling System (Pending)
5. Bennet Trim Tab Indicators (In Process)
6. XM Satelite Radio (Pending)

One down and five to go, 50 days and counting.

DonCig

[ITTLFLI]

Today was the day to start the AOTH Rocky Mountain Skunkworks projects. I received my -2" Satin Imco Shorty and had time today to mount it on the Bravo 1 outdrive. Rough measurements have the centerline of the propshaft at 4" to 6" below the bottom of the keel. I need to back the boat off the trailer a little bit to get a perfect measurement.
I have a list of 6 things to get done before AOTH.
1. Imco -2" Shorty (Done)
2. Livorsi GPS Speedo (In Process)
3. GLM Exhaust Manifolds (Pending)
4. San Juan Fresh Water Cooling System (Pending)
5. Bennet Trim Tab Indicators (In Process)
6. XM Satelite Radio (Pending)

One down and five to go, 50 days and counting.

DonCig

Looks good Don!!

[Hotspare]

Don ....

Keep this up & David's gona want his boat back ..............LOL.....

Really looks awsome ,,,,,,

You'll have to show us that nice rooster tail you bought with the shorty too ...................

See you at AOTH ..........

[roadtrip se]

Looking good Don! I want a ride at the AOTH....

Todd

[Pismo]

You may want to make item #7 full external hydraulic steering, especially with that Imco shortie.

[DonCig]

Ok Pismo, you have me thinking and now I need to ask some questiuons.

Hydraulic Steering:
1. I understand the safety concept, if a steering cable fails the sterndrive can flop to the side quickly throwing the boat in a hard turn and probably throwing the occupants out of the boat, so;
Why isn't a single ram external hydraulic ram sufficient? On racing motorcycles we just install a single steering dampner to control these kind of events, why not do the same on boats?
What does a double ram offer that a single ram does not on a single sterndive application?
I would find it easier to climb in my boat after waterskiing with just a single ram.
Why does the full system need to be hydraulic versus just the rear sterndrive portion?
Is it a simple project to install a single rear hydraulic system versus a full helm single or double instalation?
On my Classic 18 there is very little room to mount a hydraulic ram with the Bennet trim tab clyinders right in the sweet spot, yours or anybodys comments would be appreciated.


Sincerely,

DonCig

[blackhawk]

IMO a single ram does the trick. A dual ram system just adds more support to the gimbal. I would not use a tie in system. Full hydraulic or nothing. Yes, a tie in sytem may keep you from "spinning out" but in a steering failure(ie power steering belt breaks) you will have very little control. I put a full hydraulic dual ram system on my blackhawk and it made a night and day difference in the handling of the boat. My $.02

[Pismo]

Yes, the reason for Hydraulic steering is mainly to improve the handling of the boat at high speed. Added protection from gimbal/drive failure is secondary. The full hydraulic system does this best, if you do an add-on system you still have all the slop from the cable and the mechanical helm and all those linkages which just get looser and looser with time. You have an additional reason due to your Imco shortie, that large nose cone puts the lower unit tip in front of the steering pivot point of the drive causing additional instability. A full hydraulic system will improve your stability very much, an add-on will help but not as much. I have the same space problem on my 22 and am still figuring how to deal with it. A single ram is good up to 70ish mph. With a single ram you also do not need to be as concerned with mounting exactly on the centerline.

[blackhawk]

I agree Pismo. Also I don't believe that a tie-in system is any safer than the original cable sytem at all. Except for keeping pressure off the gimbal reducing the risk of gimbal failure. Also, you can mount a dual ram sytem above the centerline. Technically it's not as supportive but it's still plenty of support.

[Pismo]

To mount off the centerline you need a bypass valve in the helm or somewhere because you will be compressing both the steering rams when you trim up, counter to the normal operation of the steering rams, both in rather than one out and one in. Puts lots of added load on the seals as well. Even with the valve no more than an inch or so off center.

[blackhawk]

To mount off the centerline you need a bypass valve in the helm or somewhere because you will be compressing both the steering rams when you trim up, counter to the normal operation of the steering rams, both in rather than one out and one in. Puts lots of added load on the seals as well. Even with the valve no more than an inch or so off center.

My system must have had a relief valve somewhere then. I questioned WPM about my system and the "triangular" problem when trimming up and they stated were selling me a system that was designed to be mounted above centerline. All I know is it worked great!

[BigGrizzly]

Jim I don't know why the 27 did what it did but I had the same results with the Bravo both stock and Labbed all were not good.I did the Hydro and it was better. As everon here knows i run the Precision line of props. Years ago people on the net swore by the Marage plus, now it is the Hydro. yes my boat is different because I have a TRS drive which is suppose to be slower than a Bravo. Well the fact os prop efiency is just that regardless of what id on. Now the Hydro these guys talk about I tested years ago at Eufala and Poodle was there. I still like my TXP and Lightning better. Point is try them all and don't go labbed, because it is just fixing something that was wrong when you got it. I am converting guys here all the time. when you have a 108 MPH cat with a Hydro then you put an equivlent Precision propeller on it and it drops 500 Rpms and picks up 7MPH. so you go up an inch on the Hydro and Lose 2 MPH off the origional 108. that pretty much says it!! I say Just test all
and get off the brand idenification band wagon