Question about Speed Sensor 50 HP Merc outboard

[joezek]

I've got a 1982 4 cylinder, 50 hp outboard. It's got a built in speed sensor pickup port in the lower unit so I won't have to buy a sensor for the speedometer I'm installing. The problem is, I don't have a clue where on the engine the speedometer sense hose is supposed to connect.

I've got the original owner's manual, installation manual, and an aftermarket installation manual. The owner's manual shows exactly where the speed sensor port is located and I confirmed by looking at the lower unit that the port is installed. I just can't find where the other end of it is located so I can hook up my speedometer. The manuals show the pickup port but they don't show the connection port for the gauge.

The boat's been in the family since they bought it brand new in 1983, it's a Grumman 15 foot side console. It didn't have a single gauge in it from the factory. Since it was just given to me I've been doing minor upgrades like smart tabs, stereo, cup holders, and more importantly- gauges. At least now I know what the RPM's are, and if it's charging the battery.

 

[Chris1956]

Re: Question about Speed Sensor 50 HP Merc outboard

The hose is in the gearcase. They should be hanging out, but some folks tuck them into the gearcase if they are not using them.

 

[joezek]

Re: Question about Speed Sensor 50 HP Merc outboard

Thanks, I'll look for it after work today. I can't picture exactly where you're talking about. I've looked in the top of the outboard unit, below the engine, all around the engine. Looked for any unused hoses or capped off hose fittings. There is a plastic cover on the outside of the engine, below the main upper cowl cover. I don't think it's ever been taken of before, possibly I'll find the hose in there?

 

[Chris1956]

Re: Question about Speed Sensor 50 HP Merc outboard

Normally it is in the top of the gearcase. There is some room near the shift shaft, where the hose can be coiled up. You will likely need to drop the gearcase to get to it. If you drop the gearcase, you might rebuild the waterpump while you are at it.

You could install an external speedo pickup (Pitot) on the transom of the boat, instead.

 

[carholme]

Re: Question about Speed Sensor 50 HP Merc outboard

joezek;

Here is the parts listing for a 1982 50hp:

http://www.crowleymarine.com/mercury-outboard/275.cfm

Look under GEAR HOUSING (DRIVE SHAFT and see item 2 and the tube that is attached to it. That is the speedometer tube and that is what connects to the tube from your gauge.


Gerry

 

[joezek]

Re: Question about Speed Sensor 50 HP Merc outboard

Thanks guys, that'll help a lot. I just replaced the impeller a few months ago, but if I can't find it then I'll have no problem doing it again.