Your narrative and description of the wiring is not sufficiently complete to allow an answer to your question to be formulated.
In general, description of wiring circuit is a narrative form is difficult, often misleading, and often incomplete. Further, use of non-standard terminology for circuit components complicates the narrative form of description.
There are several problems in your narrative.
First, I do not believe that the actual information in a schematic diagram conforms to your description that a wire is to be connected to "OPTI FUEL SPICE.” I suspect you have misspelled something.
Second, that a wire is connected to "a bar" has no meaning. You must indicate what the "bar" is connected to.
I will offer what advice I can.
In a Boston Whaler boat the electrical wiring will tend to follow a set coding of wire insulation colors. In the case of a wire whose insulation is PINK, the usual coding indicates a wire with PINK insulatoin is to be attached to a fuel tank level sender. There is a comprehensive list of wire color codes in the REFERENCE section article on that topic. See
Marine Wiring Color Codeshttps://continuouswave.com/whaler/refer ... rCode.htmlThe typical FUEL TANK LEVEL SENDER will be a variable resistor. A resistor has no particular polarity in a DC circuit.
TYPICAL REMOTE ELECTRICAL TANK LEVEL GAUGE OR METER
The general arrangement for a remote gauge that indicates the fuel tank level by electrical circuits is as follows:
A source of 12-Volts (typically provided by the engine ignition key switch when the key is in the RUN or START position) will be connected to an electrical current meter, an Ammeter or more likely a MilliAmmeter. The rear face of the meter will have the terminal marked in a clear manner to indicate this is where the battery voltage is to be applied, such as a label that says I or perhaps ING for the ignition key switch which will be providing the 12-Volt power when the key is in the RUN or START position. In this way, the remote fuel tank level gauge is only operating when the engine is operating or the ignition key switch is turn to RUN from OFF without starting the engine. This conductor often has VIOLET insulation. Or a terminal might be marked B for battery. This may depend on the brand or manufacturer of the remote fuel tank level meter gauge.
Another terminal on the rear of the meter will be marked with an S (for sender). This terminal is connected to the resistive sender on the fuel tank that is to be monitored. This conductor may have PINK insulation when used with a Boston Whaler boat.
In order to complete the circuit from the fuel sender back to the gauge, a second conductor must be connected to the resistive fuel tank sender, and run back to the meter, and this may also be on a second conductor with PINK insulation. This is the negative-return conductor, and it will usually connect to a terminal marked G (for ground) on the rear face of the meter. This "G" terminal will also have a connection to the battery negative bus at the helm panel, usually made by a conductor with black insulation at the helm panel.
IMPORTANT
The reason a second conductor to return the current back to the remote meter gauge is to ISOLATE this current and to keep if from traveling on the fuel tank BONDING circuit. (See below.)
Another terminal on the rear face of the meter will typically be marked with a L (for lamp). This is the illumination circuit for the meter so it can be read in the dark. This circuit is controlled by a separate switch, often marked PANEL LIGHTS or something similar. In some instances this circuit may be from the NAVIGATION LIGHTING circuit, on the basis that if it is dark you will have illuminated the boat's navigation lamps. The gauge illumination circuit is typically run on wires with BLUE (or in some cases LT BLUE) insulation.
If the fuel tank is a made from metal, there will be a BONDING conductor that is connected to the the fuel tank. This connection is generally made to a metal tab that is welded to the fuel tank. The purpose of the BONDING conductor is to connect all the metal elements of the fuel system, especially the metal fuel inlet or filler fitting and the fuel tank. This is very important, as the flow of gasoline from the inlet fitting to the fuel tank is on a rubber hose. Due to the
triboelectric effect, the flowing of fuel can accumulate an electrical charge. The BONDING conductor should NEVER be carrying any DC current involved in any other circuit. The bonding conductor is usually a 10-AWG wire with GREEN insulation, although in some instances the insulation color might be YELLOW. The current created by the fuel tank level sender circuit SHOULD NOT be running on the bonding conductor. It should run back to the remote meter gauge.
In some instances, the resistive fuel tank level sender may NOT have an isolated return connection. The return circuit has already been completed by connecting to the the metal fuel tank. This is not the best approach as it results in some current flowing on the bonding conductors of the fuel tank. If your particular fuel tank level sender has only one terminal, then the other half of the circuit is going to be on the metal tank itself and its bonding wire. To predict what sort of resistive fuel tank level sender is in your boat is impossible for me.
Well, I have tried to use a narrative to describe the circuit, which is not a good manner. I will draw the circuit in an ASCII-TEXT diagram below:
[IGNITION KEY SWITCH TERMINAL "ACC"]-----violet wire------[FUEL GAUGE TERMINAL "I"]
[FUEL GAUGE TERMINAL "S"]-----pink wire------[FUEL SENDER CONNECTION AT FUEL TANK]
[SECOND FUEL SENDER CONNECTION AT FUEL TANK] ------second pink wire-----[FUEL GAUGE TERMINAL "G"]
[BATTERY NEGATIVE BUS at HELM] --------black wire-------[FUEL GAUGE TERMINAL "G"]