So I was just thinking last time I was in boat that my speedometer was not working, just thought it had something stuck in it. But as I got to thinking again, could this be due to changing the lower end to an IMCO shorty? I know it used to be connected to the standard lower somehow but do not know now....anyone have any ideas?

On your standard Merc drive, there is a slot cut in front of the lower housing above the bullet that picks up water for the speedo. If you trim the drive all the way up and look on top of the lower section, there is a hole with 2 small slots that accepts a yellow barbed fitting that directs the water up through the transom assembly and into the boat. I'm not sure if your IMCO lower has the water pickup in the front. If it doesn't, you will have to go with either a GPS speedo or a pitot tube setup. If it does have the pickup, most likely the barbed fitting was not reinstalled into the lower housing. I'm not real familiar with the IMCO shorties but my guess is they do not have the water pickup.

The IMCO does have some holes in the front but I am sure it only for the low water pick up for cooling. Does the speedo work off this same water pick-up?

I would think not. Only for cooling.

I have an IMCO shorty lower and it only has the water pickup and no speedo connection. I am using a GPS and my poor old Gaffrig speedo just sits there looking good on the dash!

I also added an extension box, I doubt the old tube would be big enough to go thru that too.

Anyone have any experience with MercMonitor?