Solenoid wiring, not OEM

[SenatorJoker]

I bought a new solenoid for my 90 hp Mercury outboard.
It is not original. It is a four connection solenoid.
It looks almost identical to the original except on the
center two connections it has letters. One side has an "S"
(Starter, I think) and the other side has an "I" (Ignition?).
It also has a different patterned plastic piece in the center
so I cannot use that so I cannot use that as a reference.
The original had one hot connection and one ground connection.
Which goes to hot and which goes to ground...."S' or "I"????

 

[sam am I]

Normally, if you want/need to run the typical I/O, automotive type (indicative of both the "I" and "s" terminals) on a OB, you'd just bolt the metal flange housing to the motor block (this is how its grounded), leave "I" disconnected and wire the rest like the old one........ See below




You've pictured on the left, is what appears to be this type however, with rubber mounts? This would, by default, electrically isolate the base if bolted. This is a bit odd.......... are you sure that is an "I"? The rubber mounts make me think, it an OB type....See below

Your OB wiring with your old "correct" solenoid was wired more or less as follows.........




Although yours isn't labeled, note that these types don't have/use the "I" terminal but, instead use the same terminal for solenoid's ground, #1/2. Also, by default, the metal housing on the OB types are typically floating/electrically isolated from any of the solenoids internal connections. e.g., there is no need to make sure you ground the metal flange to get it to work.

 

[SenatorJoker]

What I do not understand is every solenoid with my part number (89-817109A1) I found on the web has the "S" and "I" on it. It says it is for this motor. There is no instruction on the S & I.

 

[Silvertip]

The "I" terminal will never be used on a "magneto" based ignition system. That terminal is needed on an auto style engine with conventional ignition systems. When the key is turned to START, the "S" terminal is energized and it also sends 12 volts to the "I" to energize the auto ignition system during the starting process. Some solenoids have an "R" in that position. That is the ballast resistor bypass connection. Either way, you don't need it and it definitely does not get connected to ground.