I am restoring my 1975 Fiberform Bowrider with a 155 Mercury Outboard. The speedometer is an old Aqua Meter that was chromeplated, and you guessed it, heavily corroded. The speed goes to 55. Can anyone suggest a good replacement, preferably stainless steel, that would be compatible? It only had a plastic tube attached to the back. Don't have any idea where the tube ends up. Any info would be appreciated.
So if you have a 155 hp merc that's a 1975 it maybe a rare variety of the 1500 Merc. You should find out what you really have there.
The speedo is nothing more than an air pressure gauge. That's what the tube is, the tube goes from your speedo to an attachment on the back of the boat. It is a plastic piece that has a forward facing hole underwater and on the other end of the plastic piece is a barb that the hose pushes onto. As the boat moves forward the water pushes into the hole compressing the air in the tube, the faster the more pressure. So the increasing "pressure" is measured in MPH. Sounds weird but it works rather well. There are "in dash" or flush mount and "on dash" or flange mount style speedos. The in dash needs an approxiamte 3 5/8 inch hole, the "on dash" mount with three small screws in the outer flange, no big hole needed but, they need a small hole behind the speedo for the tube to pass through. Go on ebay and look up vintage boat speedometers you will see the different styles, some may be the same and in better condition than you have. Also look up boat pitot tubes, this is what is mounted on the back of the boat.