disconnected gauges from previous OB

[made in china]

On my 1986 Larson, the gauges are from when the boat originally had a 1986 Mercury 150 OB. The prev owner removed the 150 and installed the current 1990 Mercury 115. The 150 must have been a nicer package because it seems to have had some gauges that the 115 does not support.

Currently my dash has gauges for trim, temp, tach, speed and fuel level. Except the fuel gauge, they all appear to be original equipment Quicksilver gauges.

Only the tach and fuel level work.

The trim gauge doesn't work because the 115 I have doesn't have the option for a trim sender, as far as I can tell (it's a single ram trim). So, this gauge may need to be replaced with something else.

The Temp gauge is also inop. As far as I can tell, my motor does not currently have a temp sender on it. Is it possible to install a Mercury OEM temp sender somewhere on this motor? I have been unable to track down if it is just a simple sender that is installed where a plug may be now.

Speedometer is not working because the tubing keeps getting cut by the transom mount. Does anyone know the proper way to route the tubing down to the pitot pickup to prevent it from being cut every time the motor is raised? Is it routed externally or internally? I can't find a way to route it that it won't get cut! Also, do I need to use stiff plastic tubing to keep the MPH indication reliable?

I can see I'll probably end up replacing the trim gauge with a voltmeter.

I'd like to keep the water temp gauge, does anyone know what my options are?

Regarding the trim sender, am I correct that it's not an option for my motor setup?

Thanks for the help!

 

[Chris1956]

Re: disconnected gauges from previous OB

Trim gauge is useless on an outboard powered boat. Trim it by feel. Replace the water temp gauge with a water pressure gauge. It is more useful as it will tell you when your motor is about to overheat. That motor should have an overheat alarm anyway.

 

[achris]

Re: disconnected gauges from previous OB

...The Temp gauge is also inop. As far as I can tell, my motor does not currently have a temp sender on it. Is it possible to install a Mercury OEM temp sender somewhere on this motor? I have been unable to track down if it is just a simple sender that is installed where a plug may be now.

Temperature pickup is usually just contact with the cylinder head. As you engine has a fully water jacketed head, you can't use a temperature gauge. As I said in an earlier thread, and Chris1956 has said here, put in a water pressure gauge. Much more value.

Speedometer is not working because the tubing keeps getting cut by the transom mount. Does anyone know the proper way to route the tubing down to the pitot pickup to prevent it from being cut every time the motor is raised? Is it routed externally or internally? I can't find a way to route it that it won't get cut! Also, do I need to use stiff plastic tubing to keep the MPH indication reliable?

I usually run the tubing into the engine cover with the electrical harness, then down through the bottom cowl where the trim motor wires go, and on down to the fitting on top of the gear housing, never seen one cut that way. Just use the plastic tube that comes with the gauge.

I can see I'll probably end up replacing the trim gauge with a voltmeter.

I'd like to keep the water temp gauge, does anyone know what my options are?

There aren't any. Put in a water pressure gauge.

Regarding the trim sender, am I correct that it's not an option for my motor setup?

You are correct....

C.........

 

[Silvertip]

Re: disconnected gauges from previous OB

Some mis-information here. First - a water pressure gauge will not tell you when the engine is about to overheat. it does tell you whether or not the water pump is working. A perfectly functioning water pump is no guarantee an engine will not overheat. Malfunctioning poppet (bypass) valves and thermostats can cause an overheat. Temperature senders are available that can be adapted to nearly any outboard. In the case of your 115, look in the upper right corner at the top of the water cover for a plug. If there is one, a temp sender can be inserted in that port. There is also a contact style kit that installs under a water cover bolt. Instructions come with the gauge and sender. That port can also be used for a water pressure guage. Here is a picture of a 75 Merc that shows the port I'm referring to.

And here is how you can install a water pressure gauge. No sender is required.

 

[achris]

Re: disconnected gauges from previous OB

S.... Temperature senders are available that can be adapted to nearly any outboard. ...

You got a part number for that sucker?... I've never seen one on a 3/4 cylinder before... Is it a Merc accessory?

C.......

 

[Silvertip]

Re: disconnected gauges from previous OB

It is the very same temp sender (threaded style) that you can order from Teleflex/Faria. It has the normal 33 - 240 resistance range and any U.S. standard temp gauge can be used with it. Don't have the numbers in front of me at the moment. This same sender can be mounted on what's called a "Z" bracket. The tip of the sender contacts the cylinder head and the sender screws into the bracket which is attached via a water cover (or cylinder head) bolt.