"New to me" 2005 Mercury 90HP question

BryanKipp

Cadet
Joined
Jul 17, 2015
Messages
11
I just recently purchased a "new to me" 2004 pontoon boat. It has a 2005 90HP Mercury outboard, model number 1F90412DD, serial number 1B008689. Since I am new to outboards (previously have had I/O) and am attempting to get everything functioning as it should, I have a couple newbie questions. Where I get stuck is the speedometer. I believe, from my research, that the pickup tube for speed is in the lower unit on the motor. I currently have a small piece of rubber tubing sticking out of the front of the motor approximately 3" but it's not connected to anything from there. It comes out of the front just under the lower steering connection. Is this the tube for the speedometer?
I also found what appears to be an insulating sleeve that is tied together with the wiring harness that has nothing in it. I'm wondering if that might be for the trim gauge since the sender is .not installed.(Bolts are there, but the sender appears to have been broken off)
Is there a diagram anywhere that shows the connections on the motor and gauge ends? I had one for my I/O but can only find ignition diagrams for the outboard.

Any assistance would be greatly appreciated! I can provide pictures of the two tubes mentioned if needed.
Thanks!
 

ThomW

Chief Petty Officer
Joined
Aug 8, 2016
Messages
615
Pictures would definitely help. You are correct that the Speedo for the out board is a little pin hole on the lower unit, with a small rubber hose that comes up through lower and into motor, then connects to a hose running up to the dash. It senses air pressure from the water rushing past the lower and sends that to the gauge. They are not super reliable, and a lot of times when someone works on the lower unit, the hose gets disconnected and never re-connected. Is there another piece of similar hose coming back from the dash area anywhere? If so, just take a double ended male adapter and connect the two. You can look under console and see if there is a tube coming from speedometer gauge and follow that back to see where it ends.

As for the other part, not sure what was in it.
 
Top