View Full Version : Solenoid differences -the mysterious S & I terminals

06-27-2010, 12:36 PM
The boat is a ’76 w/ 351W, point style ignition. After a recent engine stoppage and tow in, I did some testing at home, the problem sure looked like the solenoid – voltage everywhere it should be but no clicking. Short on time, a local boat shop suggested and early 70’s Ford “CAR” solenoid . At the auto parts store they appeared identical
So put the new “CAR” solenoid on – problem was exactly the same, voltage everywhere but no clicking. A buddy and I spent a crazy amount of time trying to understand the “S” & “I” terminals on the backside. Did some searching on the forum here and found others have been befuddled w/ these little posts.
Fast forward, we put the “MARINE” solenoid back on and the boat fired right up. I suspect the problem was a poor ground but we never had hard evidence

Here’s my confusion and question
Bench testing the “CAR” and “MARINE” solenoids, off the boat – there is continuity between the “S” & “I” terminals on the “MARINE” solenoid, however there is no continuity between the same terminals on the “CAR” solenoid??
Are these solenoids truly different and why?

06-27-2010, 07:21 PM
Napagary, I just did the same thing with my boat. As you did put on a "Car" solenoid mine didnt turn over and NO click sound with mine. I went to a local boat shop put on the marine one fired right up. I have the same motor as you do a 351W. I know that the "S" side is for the starter side from the safty neutral on the tranny for the "I" side nothing goes to it lave it open. I wish I had other info for you than that but I am sure someone will say why and how a car one will not work.

06-27-2010, 07:44 PM
Thanks, sure frustrating isn't it? Maybe we'll get some movers and shakers to educate us?