CMI Gen X/Hardin/SM????
09-05-2011, 07:55 PM
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CMI Gen X/Hardin/SM????
I know this topic has been beat to death...but a re-vote would be a huge favor. 
Our 42 2005 Ftn is currently @ RF Powerboats getting re-rigged. Just had new 540CI 1000HP Dart Block motors w 3.3L whipples built by Tyler Crockett. The current tailpipe setup is rigged for CMI's. As much as I hate to admit it...I was not fully aware of the 525 OE CMI issues. Last thing I want to do is smoke these new power plants due to the apparent issues on the OE CMI's.
So....lets hear it. Gen X CMI's, Hardin, SM, KE? Anyone's input/experience would be greatly appreciated.
Thank you.
Our 42 2005 Ftn is currently @ RF Powerboats getting re-rigged. Just had new 540CI 1000HP Dart Block motors w 3.3L whipples built by Tyler Crockett. The current tailpipe setup is rigged for CMI's. As much as I hate to admit it...I was not fully aware of the 525 OE CMI issues. Last thing I want to do is smoke these new power plants due to the apparent issues on the OE CMI's.
So....lets hear it. Gen X CMI's, Hardin, SM, KE? Anyone's input/experience would be greatly appreciated.
Thank you.
09-06-2011, 03:19 PM
#2
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Just checked out you pictures on the Fountain forum. Great looking boat.
As far as current set up on headers, you have two different style headers, the port motor has taller headers with straight collectors, the starboard motor uses the standard turn down bravo style headers. Currently CMI, only makes the Gen X in the turn down style. To run them on both motors, you would have to get the port motors tail pipes modified to fit. But I think that what ever you run, if they are not CMI's you will have to change the mating collars on the tail pipes to match the new exhaust.
Just went through this with our 38/700 boat. Used the Gen X's and changed the tail pipes on the port motor.
As far as current set up on headers, you have two different style headers, the port motor has taller headers with straight collectors, the starboard motor uses the standard turn down bravo style headers. Currently CMI, only makes the Gen X in the turn down style. To run them on both motors, you would have to get the port motors tail pipes modified to fit. But I think that what ever you run, if they are not CMI's you will have to change the mating collars on the tail pipes to match the new exhaust.
Just went through this with our 38/700 boat. Used the Gen X's and changed the tail pipes on the port motor.
09-06-2011, 06:00 PM
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Just checked out you pictures on the Fountain forum. Great looking boat.
As far as current set up on headers, you have two different style headers, the port motor has taller headers with straight collectors, the starboard motor uses the standard turn down bravo style headers. Currently CMI, only makes the Gen X in the turn down style. To run them on both motors, you would have to get the port motors tail pipes modified to fit. But I think that what ever you run, if they are not CMI's you will have to change the mating collars on the tail pipes to match the new exhaust.
Just went through this with our 38/700 boat. Used the Gen X's and changed the tail pipes on the port motor.
As far as current set up on headers, you have two different style headers, the port motor has taller headers with straight collectors, the starboard motor uses the standard turn down bravo style headers. Currently CMI, only makes the Gen X in the turn down style. To run them on both motors, you would have to get the port motors tail pipes modified to fit. But I think that what ever you run, if they are not CMI's you will have to change the mating collars on the tail pipes to match the new exhaust.
Just went through this with our 38/700 boat. Used the Gen X's and changed the tail pipes on the port motor.
09-08-2011, 12:10 PM
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just go with the SM GEN3 4.5 or 5'' and youll never have to worry about leaks again...the boat isnt going to see the difference of 10hp between apliations,,, put you will have peace of mind for all the money you have already spent
09-08-2011, 06:22 PM
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Leaning that way....but need to redo exhaust pipes if we go SM route. Theres another 5k...lol.
09-09-2011, 03:55 PM
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If you runing 540's and 1000 HP's the chances are you didn't have (or have) the std CMI headers. You might have the heavier dutty thicker system. Even the Gen X have some issues, not just the headers for the 525's There is more 525's out there then just about anything else, so it's more frequent.
CMI "big top" headers are ok. There is a lot you can do to eliminate header issues.
A) Make a connector rod (just like an outdrive tie bar) on the top of the headers, COnnect port to srbrd. This will reduce viboration and movevement left to right. No movement= no cracks. The hole set needs to move with the block. CMI's have an issue at the connection of the inner tube at the flange, weak area... so with the tie rod you stiffen the system up.
B) Make sure you use a heavy duty, wire filled rubber tail pipe to tip exhaust connection hose. Again, Stiffens the set up.
C) Drain the headers EVERY TIME AFTER USE.
And remember. Pretty much ALL headers will leak one time or another, one way or a nother. THe key is to keep the water out of the engine. WHile running, exhaust will push it out and while hot, most will eveporate. Once you stop, that's when water can get back into the engines. I learned some of the chit the hard way but since I done all this and more, I had no problems.
CMI "big top" headers are ok. There is a lot you can do to eliminate header issues.
A) Make a connector rod (just like an outdrive tie bar) on the top of the headers, COnnect port to srbrd. This will reduce viboration and movevement left to right. No movement= no cracks. The hole set needs to move with the block. CMI's have an issue at the connection of the inner tube at the flange, weak area... so with the tie rod you stiffen the system up.
B) Make sure you use a heavy duty, wire filled rubber tail pipe to tip exhaust connection hose. Again, Stiffens the set up.
C) Drain the headers EVERY TIME AFTER USE.
And remember. Pretty much ALL headers will leak one time or another, one way or a nother. THe key is to keep the water out of the engine. WHile running, exhaust will push it out and while hot, most will eveporate. Once you stop, that's when water can get back into the engines. I learned some of the chit the hard way but since I done all this and more, I had no problems.
Last edited by PARADOX; 09-09-2011 at 03:58 PM.
09-09-2011, 10:37 PM
#8
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Paradox is correct. I have one boat (an Avanti) running a set since 2000 using his methods.
Just a note, one can easily make full-time header drains; just run a hose from the rear of the distribution tube through a bulkhead fitting on your transom (on each header of course). The headers then drain every time you shut the engine down. The side benifit is this allows you to size your drains to bleed off excess water perssure, keep sizing up until you like the WOT pressures.
Just a note, one can easily make full-time header drains; just run a hose from the rear of the distribution tube through a bulkhead fitting on your transom (on each header of course). The headers then drain every time you shut the engine down. The side benifit is this allows you to size your drains to bleed off excess water perssure, keep sizing up until you like the WOT pressures.
09-10-2011, 02:09 PM
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If you runing 540's and 1000 HP's the chances are you didn't have (or have) the std CMI headers. You might have the heavier dutty thicker system. Even the Gen X have some issues, not just the headers for the 525's There is more 525's out there then just about anything else, so it's more frequent.
CMI "big top" headers are ok. There is a lot you can do to eliminate header issues.
A) Make a connector rod (just like an outdrive tie bar) on the top of the headers, COnnect port to srbrd. This will reduce viboration and movevement left to right. No movement= no cracks. The hole set needs to move with the block. CMI's have an issue at the connection of the inner tube at the flange, weak area... so with the tie rod you stiffen the system up.
B) Make sure you use a heavy duty, wire filled rubber tail pipe to tip exhaust connection hose. Again, Stiffens the set up.
C) Drain the headers EVERY TIME AFTER USE.
And remember. Pretty much ALL headers will leak one time or another, one way or a nother. THe key is to keep the water out of the engine. WHile running, exhaust will push it out and while hot, most will eveporate. Once you stop, that's when water can get back into the engines. I learned some of the chit the hard way but since I done all this and more, I had no problems.
CMI "big top" headers are ok. There is a lot you can do to eliminate header issues.
A) Make a connector rod (just like an outdrive tie bar) on the top of the headers, COnnect port to srbrd. This will reduce viboration and movevement left to right. No movement= no cracks. The hole set needs to move with the block. CMI's have an issue at the connection of the inner tube at the flange, weak area... so with the tie rod you stiffen the system up.
B) Make sure you use a heavy duty, wire filled rubber tail pipe to tip exhaust connection hose. Again, Stiffens the set up.
C) Drain the headers EVERY TIME AFTER USE.
And remember. Pretty much ALL headers will leak one time or another, one way or a nother. THe key is to keep the water out of the engine. WHile running, exhaust will push it out and while hot, most will eveporate. Once you stop, that's when water can get back into the engines. I learned some of the chit the hard way but since I done all this and more, I had no problems.
09-10-2011, 02:10 PM
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Paradox is correct. I have one boat (an Avanti) running a set since 2000 using his methods.
Just a note, one can easily make full-time header drains; just run a hose from the rear of the distribution tube through a bulkhead fitting on your transom (on each header of course). The headers then drain every time you shut the engine down. The side benifit is this allows you to size your drains to bleed off excess water perssure, keep sizing up until you like the WOT pressures.
Just a note, one can easily make full-time header drains; just run a hose from the rear of the distribution tube through a bulkhead fitting on your transom (on each header of course). The headers then drain every time you shut the engine down. The side benifit is this allows you to size your drains to bleed off excess water perssure, keep sizing up until you like the WOT pressures.
