Mercury 2.5 Late 90's versus 2000's

[Glastron1987]

For a used engine I like the Mercury 1993-1998 or so 2.5L V6's, but I notice after the late 90's into the 2000's there were some changes.

What I notice is that the cowling changed, and that the heads went to an o-ring seal.

Are these changes real improvements, or mostly just differences?

Are there other differences or improvements to these later model engines worth noting?

[Dave S]

The O ring heads came w/cdm ingt....you are hard pressed to find.... ome. 2.5 head gaskets....The early 2.5s had 7 peddel reeds Small bottom guided rods/ pistons.....Latter had 5 reeds top guided rods pistons.......that had plastic cages on rod bearings that droop and blast..... HeeHee......The latter blocks....1996 have the best FF w/ head gaskets.... easy to mill...but them bearings......early blocks were needing work.... the ports were in need of work ff blocks were better on the exhaust chest.....

[Merc 2.5]

Usually people will deck the block .040-.045 thou and run gasket and gasket heads , I hear the cdm ignition will have a better hole shot from stock , but I still like the switch box ignition , but I wouldnt call it a upgrade but some might

[Dave S]

Yes toooo 2.5..... but finding good oem head gaskets might be an issue.....easy to mill the heads .....but the O ring heads are ok.... just what you can live with.

[Glastron1987]

Usually people will deck the block .040-.045 thou and run gasket and gasket heads , I hear the cdm ignition will have a better hole shot from stock , but I still like the switch box ignition , but I wouldnt call it a upgrade but some might

Are we saying there are no more switch boxes with the CDM ignition?

[Noah Burns]

Are we saying there are no more switch boxes with the CDM ignition?

yes, like a 280 has no switches, but an ECU instead.

[Merc 2.5]

Are we saying there are no more switch boxes with the CDM ignition?

Correct

[Glastron1987]

yes, like a 280 has no switches, but an ECU instead.

Even on the carbureted engines, no switch boxes but an ECU?

[tlwjkw]

not ecu's as normally thought of.. called "control module" or "ecm".. carb and efi… they are 'bout tha same size as a oiler module.

[Glastron1987]

So any performance or reliability gains with the ECM system compared to having the switch boxes?

[Merc 2.5]

I hear hole shot was little better but that's n stock form. , I haven't ever owned or messed with cdm tho, does timing adjust like a switch box mota? Idk like I said never owned or messed with em. But u wouldnt have to worry bout switch box messin up

[Motv18]

The cdm is also just 6 switch box modules. The last longer with less load.

Switch box runs one capacitor and one scr per three coils vs. cdm running a scr and capacitor per coil.

The rest takes a book a lot to put in a post description.

[Merc 2.5]

The cdm is also just 6 switch box modules. The last longer with less load.

Switch box runs one capacitor and one scr per three coils vs. cdm running a scr and capacitor per coil.

The rest takes a book a lot to put in a post description.

Is the timing adjusted like switch box motor?

[tlwjkw]

big difference ina "switch box" motor anda cdm motor.. you can tune and/or set up a switch box motor to turn whatever tha motor will stand/ built ta go... a cdm is limited by tha ecm (merc electronic product and can't be changed and won't run without it) module and will not run with tha switch box motor..... only exception is tha 280..

look at a 2000 and above 150/200 V6 and compare to 1999 and below and you will see all tha differences in tha ignition parts... 2

[tlwjkw]

Is the timing adjusted like switch box motor?

yep, but tha module controls it thru all tha ranges.. also limits it and rpm...…….

[Merc 2.5]

big difference ina "switch box" motor anda cdm motor.. you can tune and/or set up a switch box motor to turn whatever tha motor will stand/ built ta go... a cdm is limited by tha ecm (merc electronic product and can't be changed and won't run without it) module and will not run with tha switch box motor..... only exception is tha 280..

look at a 2000 and above 150/200 V6 and compare to 1999 and below and you will see all tha differences in tha ignition parts... 2

I thought it was sumthin like this and also thought switch h box can run better tune better , but wasnt sure so didnt wanna say it. But I always heard the xr6 cdm motor if was swapped to switch box ran quite bit better

[tlwjkw]

its jus fact that you an do a lot more with a switch box motor.... in tha 'ole days anyway..:leaving:

[Glastron1987]

big difference ina "switch box" motor anda cdm motor.. you can tune and/or set up a switch box motor to turn whatever tha motor will stand/ built ta go... a cdm is limited by tha ecm (merc electronic product and can't be changed and won't run without it) module and will not run with tha switch box motor..... only exception is tha 280..

look at a 2000 and above 150/200 V6 and compare to 1999 and below and you will see all tha differences in tha ignition parts... 2

From the diagram I see the "CDM Module Assembly" (#14 below). It confused me a little because I thought someone compared it to looking like an oil control module, which looks like switch boxes to me, and these CDM modules look more like a coil to me.

So it sounds like this CDM system should be a step up in reliability, but a step down in being able to modify your engine to increase rpms. I wonder what the rpm limit would be using this? I'm happy with staying under 6500.
458281

[tlwjkw]

From the diagram I see the "CDM Module Assembly" (#14 below). It confused me a little because I thought someone compared it to looking like an oil control module, which looks like switch boxes to me, and these CDM modules look more like a coil to me.


compared tha "control" module ta lookin' kinda like tha oiler module.
.
a little fatter.


So it sounds like this CDM system should be a step up in reliability, but a step down in being able to modify your engine to increase rpms. I wonder what the rpm limit would be using this? I'm happy with staying under 6500.

ya really close with this description.. rpm and all....
458281

….................. :thumbsup:

[Glastron1987]

Just noticed one more difference with CDM... the spark plugs have a gap. I've always loved not having to fool with gaps on the older ones, and never had a failure either.

[FORBESAUTO]

On the cdm, the coils are called cdm units. They receive the voltages from the stator and contain the capacitors. There is also a module mounted on top of motor that gets the signal from the trigger, process timing needs, rev limiter and such and sends signal to cdms when to fire. System is reliable, doesn’t allow full timing advance until above 5k rpm which softens take off/ accel. Rev limiter should be around 5800 rpm. The switchbox system is all manual and can adjust it to what you want it to do, which is why it’s preferred in most performance instances. If someone could successfully program the module on the cdm, it would be great because you could have even more control, but I know if no one doing it. Tried getting the limiter removed on one and after three failed attempts I gave up on cdms

[Glastron1987]

On the cdm, the coils are called cdm units. They receive the voltages from the stator and contain the capacitors. There is also a module mounted on top of motor that gets the signal from the trigger, process timing needs, rev limiter and such and sends signal to cdms when to fire. System is reliable, doesn’t allow full timing advance until above 5k rpm which softens take off/ accel. Rev limiter should be around 5800 rpm. The switchbox system is all manual and can adjust it to what you want it to do, which is why it’s preferred in most performance instances. If someone could successfully program the module on the cdm, it would be great because you could have even more control, but I know if no one doing it. Tried getting the limiter removed on one and after three failed attempts I gave up on cdms

Oh very interesting. Thanks.

[Aaronhl]

Is the idle and wide open timing set the same way as the switchbox engines?

[OnPad]

See post 15.

[Aaronhl]

Thank U overlooked that maybe I was on a different thread

[OnPad]

I think just the first years of 2000's/cdm have the same timing arm. The later versions I don't know much about. Thinkin they switched to Motorola electrics, and alternator..? Might be more like a 3 litre setup..?