Originally Posted by twistedtree
I agree itís a diode to clamp the reverse EMF from the coil when itís released. That limits the pulse going back to whatever is controlling the solenoid, possibly the ECU.
That said, some solenoids have the clamping diode built in. Try measuring the resistance across the diode in both directions. It should be high in one direction and low in the other. Then try the same across the coil terminals in the solenoid. Both directions will be low because of the coil windings, but one lower than the other. Iíd be interested to hear what you find.
TT, thanks for info. Using my multimeter red to red and black to black on the diode measures OL and in reverse 2.2 ohms (or .58v). Iím not on the boat so canít measure across the solenoid terminals. On the new relay the resistance is 27.7 ohms in both directions. With the diode measuring high in only one direction which terminal the red and black diode wires connect to matter but there is no + or - markings on the relay. Iím inclined to use the relay without the diode, if it craps out prematurely I have a spare at which time IĒlol know to add the diode.