IMCO SCX Conversion to SCXT?

[DarkHorseRacing]

Hey everyone,

Thinking about my cone clutch IMCO SCX drive, it drives me nuts shifting it because the engine is borderline on the recommended rpm and sometimes doesn't totally drop rpms enough and the result is a good hard clunk when it shifts. I cant imagine that's any good on the cone clutch. I've been spoiled by our other boat that has a Velvet digital shift transmission and its like shifting a car its so smooth.

So, the question is, what would it take to add the IMCO extension box and transmission and turn this SCX into an SCXT? Would you simply take the cone clutch out of the SCX and replace with a regular shaft? Obviously have to buy the extension box and transmission and have that mounted to the boat. Does that take a different bolt pattern and require major transom work?

It seems the extension box really pulls the drive up, which could change the dynamics of how the boat handles and runs, so I'm sure there would be more cons than pros to this.

Anyone know what transmission IMCO uses in this setup? Like a BAM or Huber or Velvet? - ETA: Their website says BAM so thats the answer to that.

 

[RiverDave]

You know people have questions and generally someone will have the answer, but I think you are gonna have to call IMVO on that one.

 

[Bobby_329]

Hey everyone,

Thinking about my cone clutch IMCO SCX drive, it drives me nuts shifting it because the engine is borderline on the recommended rpm and sometimes doesn't totally drop rpms enough and the result is a good hard clunk when it shifts. I cant imagine that's any good on the cone clutch. I've been spoiled by our other boat that has a Velvet digital shift transmission and its like shifting a car its so smooth.

So, the question is, what would it take to add the IMCO extension box and transmission and turn this SCX into an SCXT? Would you simply take the cone clutch out of the SCX and replace with a regular shaft? Obviously have to buy the extension box and transmission and have that mounted to the boat. Does that take a different bolt pattern and require major transom work?

It seems the extension box really pulls the drive up, which could change the dynamics of how the boat handles and runs, so I'm sure there would be more cons than pros to this.

Anyone know what transmission IMCO uses in this setup? Like a BAM or Huber or Velvet? - ETA: Their website says BAM so thats the answer to that.

Did you ever find out anything on this? I am in the same situation. Already have the scx but would much rather have a trans than the cone clutch.

 

[chadzilla]

I have this set up in our Hallett 335. Imor 625's with Imco sct's which were the predecessor to the scx or scxt. You will need to purchase complete scxt upper gearcases. The internals are completely different except for the gears. You will also need IMCO transmission mounts, trans style bellhousings, trans drive plates and of course the stand off box and transmission. Steering, depending on what you have, will also have to be modified. Honestly you would be better off selling what you have as a complete setup and purchasing the complete kit from IMCO, drive and all. There shouldn't be any modifications needed to the transom of the boat as the box has a much larger opening and bolt pattern. Ours uses BAM 1350 transmissions. The box itself does not have any "rise" built into it unlike a Stellings. You will have to determine the correct "X" dimension.

 

[DarkHorseRacing]

Did you ever find out anything on this? I am in the same situation. Already have the scx but would much rather have a trans than the cone clutch.

Well per chadzilla’s post describing the process it was more trouble and money than it was worth.

I wound up just adjusting my throttle stop down slightly to force the engine to idle lower. It doesn’t idle as smooth now but the rpms are finally where the drive shifting is no longer a problem.

 

[Deano]

Have you considered a shift interupter switch to momentarily cut the ignition?

 

[pixrthis]

Have you considered a shift interupter switch to momentarily cut the ignition?

Or removing the neutral safety switch and put it in gear and then start the boat. It’s a pain in the ass but I’ve done it for years.

 

[Ren]

I really like how my bam 1350 shifts, smooth like a car. Hooked up to a Konrad ace drive. Its my 1st season with it so cant say much else but i like it so far.

 

[DarkHorseRacing]

So does anyone know what this thing is? I thought it was shift interrupter but I/Os aren’t my area.

 

[HST4ME]

Mercury Racing SSM #6 Dry Sump Drives & Gimbals Rebuilt FRESH

Mercury Racing SSM #6 Dry Sump Drives & Gimbals Rebuilt FRESH

www.chiefpowerboats.com

Someday you guys will get it

 

[ChrisV]

Mercury Racing SSM #6 Dry Sump Drives & Gimbals Rebuilt FRESH

Mercury Racing SSM #6 Dry Sump Drives & Gimbals Rebuilt FRESH

www.chiefpowerboats.com

Someday you guys will get it

We all can dream.

 

[DarkHorseRacing]

Mercury Racing SSM #6 Dry Sump Drives & Gimbals Rebuilt FRESH

Mercury Racing SSM #6 Dry Sump Drives & Gimbals Rebuilt FRESH

www.chiefpowerboats.com

Someday you guys will get it

We have a 30 Eliminator with a 6 drive in the family. Shifts like a dream. I was just trying to find out how close I can get while using the SCX I already have on my boat since I know IMCO offered the trans version.

Sounded like an easy swap until Chadzilla brought up the long list of stuff to change that would essentially be a complete re-rig.

 

[Boat 405]

I went down the same rabbit hole. Just set your idle lower and try to stall the motor momentarily. Shift. Then bump the throttle back up. Been doing it this way for years now. Sucks to play throttle jockey around the dock but it works. 150 hrs on my first scx prior to tearing it down and no significant problems. Put in a new clutch and lower sc gears. My deal is a naturally aspirated 582 with a carb. Makes 860 hp. 272 duration at .050 with a 112 lobe sep. exhaust is dry to the tip to prevent water ingestion. Doesnt like to idle under 1000 rpm.

 

[HST4ME]

So does anyone know what this thing is? I thought it was shift interrupter but I/Os aren’t my area.

Someone set it up to have an alpha shift interrupt. Whether the cable load is high enough to trip it is another thing

 

[Bobby_329]

I have no neutral safety switch and have been driving it like a flat bottom. Part of my issue is I'm running 1.25 and a 30p so that shift wants to kill the motor with the idol down lower. Im all good with starting in gear but around the dock and other boats that may or may not know what they are doing it becomes a pain. But sounds like the fix would cost more than its worth to just deal with it.

 

[chadzilla]

So does anyone know what this thing is? I thought it was shift interrupter but I/Os aren’t my area.

That is an Alpha shift plate that has a bravo arm on it. The thought was good, but I seriously doubt it actually works and here is why. The Alpha shift interrupt switch is activated when the operator shifts from in gear to neutral, not when going into gear. I doubt there is enough resistance or tension on the cable when going into gear on a bravo to activate the switch. Mercury started installing shift anticipation switches on bravo equipped boats in 2001 that actually work really well. They send a signal to the ecm which reduces rpm when shifting. Mercury racing had a really innovative system on their 900sc engines back in the day. They had a dashpot attached to the throttle linkage on the rear carb that was activated by the ignition module. The module was triggered by the shift switch on the transmission. When the driver shifted into gear, the dashpot would open the throttle ever so slightly to prevent stalling when going into gear. It worked very well. For the life of me, I still dont understand why engine builders would ever replace that system with an MSD or Daytona system which were both inferior but they did. Maybe they just didnt understand it.

 

[DarkHorseRacing]

That is an Alpha shift plate that has a bravo arm on it. The thought was good, but I seriously doubt it actually works and here is why. The Alpha shift interrupt switch is activated when the operator shifts from in gear to neutral, not when going into gear. I doubt there is enough resistance or tension on the cable when going into gear on a bravo to activate the switch. Mercury started installing shift anticipation switches on bravo equipped boats in 2001 that actually work really well. They send a signal to the ecm which reduces rpm when shifting. Mercury racing had a really innovative system on their 900sc engines back in the day. They had a dashpot attached to the throttle linkage on the rear carb that was activated by the ignition module. The module was triggered by the shift switch on the transmission. When the driver shifted into gear, the dashpot would open the throttle ever so slightly to prevent stalling when going into gear. It worked very well. For the life of me, I still dont understand why engine builders would ever replace that system with an MSD or Daytona system which were both inferior but they did. Maybe they just didnt understand it.

Well I notice there is an electrical connection going to that plate. What would happen if I disconnected it?

 

[DarkHorseRacing]

Someone set it up to have an alpha shift interrupt. Whether the cable load is high enough to trip it is another thing

When you say cable load, you mean how easy or hard it is to shift into or out of gear? It’s easier to shift into gear, pulling it out of gear is a little more tension.

One of the reasons why I asked about converting to the SCXT was this setup stalls constantly shifting into or out of gear. I originally thought it was the shift plate thing, or maybe the ecu wasn’t getting the signal, or I needed to replace the shift control. It doesn’t stall at all left in neutral.

Turns out, adjusting the throttle stop to introduce the IAC seemed to be the solution. It was previously not involved in startup and idle as the idle was high enough it wasn’t using it. It’s gone from stalling constantly when shifting to rarely doing it.

 

[Boat 405]

I have no neutral safety switch and have been driving it like a flat bottom. Part of my issue is I'm running 1.25 and a 30p so that shift wants to kill the motor with the idol down lower. Im all good with starting in gear but around the dock and other boats that may or may not know what they are doing it becomes a pain. But sounds like the fix would cost more than its worth to just deal with it.

Dang. 1.25 gear and 30p. You bump it into gear and the boat moves about a boat length... Its' a pain I understand

 

[chadzilla]

Well I notice there is an electrical connection going to that plate. What would happen if I disconnected it?

Well i am not entirely sure. There were 2 different styles of switch. One was normally open and shorted the ignition to ground when activated and the other was a normally closed that interrupted positive voltage when activated. It sounds as if you remedied the problem though by adjusting the throttle blades so the IAC is actually controlling the idle. That is the correct way of doing it. Traditionally, I always want to see the IAC at 30-50% when idling out of gear and the throttle completely closed. That way it has the ability to open up and keep the engine idling when shifting. You might also want to check your TPS voltage now that you have adjusted the throttle blade. It should be between .45v and .75v. That is a generality and some engines end up more or less.

 

[HALLETT BOY]

I have an SCX 1.5 w a 30P Maximus , when you drop into gear it does clunk a little and starts moving right away . I have changed fluid twice , and no metal or burn smell at all . That being said , I would go with a transmission next time .

 

[DarkHorseRacing]

I have an SCX 1.5 w a 30P Maximus , when you drop into gear it does clunk a little and starts moving right away . I have changed fluid twice , and no metal or burn smell at all . That being said , I would go with a transmission next time .

So would I. And I’d also go with the dual down shaft lower.

 

[chadzilla]

I have an SCX 1.5 w a 30P Maximus , when you drop into gear it does clunk a little and starts moving right away . I have changed fluid twice , and no metal or burn smell at all . That being said , I would go with a transmission next time .

Here is some secret squirrel info on the SCX. You will never see metal on the plug or in the oil until it grenades. There is a plate screwed to the floor of the upper gear housing from the bottom side that has a very strong magnet welded to it. All of the metal in the oil will eventually stick to it. The only way to inspect/clean the magnet is to separate the cases and flip the upper upside down so you can access the plate. It is held with I think 6 allen head screws. Unbolt it and you will see the magnet.

 

[Howardflat]

I'm not an expert in any of this but maybe money better spent might be with adding fuel injection and electronic ignition to get your idle and shifting under control. Doing the transmission route is going to add a ton of weight right on the transom, mess with the drive height and rob some power. Just a thought.

 

[HST4ME]

Here is some secret squirrel info on the SCX. You will never see metal on the plug or in the oil until it grenades. There is a plate screwed to the floor of the upper gear housing from the bottom side that has a very strong magnet welded to it. All of the metal in the oil will eventually stick to it. The only way to inspect/clean the magnet is to separate the cases and flip the upper upside down so you can access the plate. It is held with I think 6 allen head screws. Unbolt it and you will see the magnet.

^^^^ this.

They are just a big bravo, with all the bravo problems and the cost just slides up the scale. I have one more set to do and I will never accept them in the shop again.

Fucking cracks me up when "virgin drives" show up and that magnet looks like a christmas tree. If you want to play, buy the right shit in the first place.

 

[DarkHorseRacing]

I'm not an expert in any of this but maybe money better spent might be with adding fuel injection and electronic ignition to get your idle and shifting under control. Doing the transmission route is going to add a ton of weight right on the transom, mess with the drive height and rob some power. Just a thought.

If you’re referring to me I have a TCM 825 EFI already. Boat has no real issues at Havasu, all my problems start when I bring the boat up to Arrowhead. I didn’t think I’d need to change anything to run an EFI boat at elevation but I clearly had to mess with the throttle and IAC.

It’s still not perfect but it’s way better than it was. If I knew I was going to wind up with this boat on Arrowhead I would have chosen the Merc 600SCi instead.

 

[Bobby_329]

I'm not an expert in any of this but maybe money better spent might be with adding fuel injection and electronic ignition to get your idle and shifting under control. Doing the transmission route is going to add a ton of weight right on the transom, mess with the drive height and rob some power. Just a thought.

Probably where I will end up but mine is a gentry twin turbo setup and I have no idea what I'm doing with efi it will have to go to GT.