1968 Mark Twain V Sonic Trim Problem
This post is not necessarily about need for advice on a fix but to tell you one of the fixes we did to get our "new" boat on the water.
This past winter, we purchased a 1968 MT V Sonic 20'. And, of course, we get it on the water in the spring only to find that the I/O trim isn't working. The trim will work part of the way and then totally stop. After investigating, we come to find that the previous owner (one back from the guy who sold it to us) had more or less torn out the wiring of the boat and put it all back together with bubblegum and paperclips. For example, we all know a red wire is the hot wire, right? Not on this boat, baby! Noooo, red was used for hot AND ground, making it an absolute joy to figure out what when it comes to electric. And that's what led to the trim motor burning out (we think). Or it could have been that the boat is 50 years old, and things just burn out at some point. Then there were extraneous purple wires that went to nowhere, because they had been ripped out of the jacket on the original pump.
Anyway, we were fortunate to find a local boat dealer who had shelves of parts that had been salvaged over the years. The good news was that the fix was only about $100. I can say "only" because we know it's not hard to dump thousands in to a boat fix. The problem was figuring out how it all went to the solenoid, because the guy two owners prior thought it wise to remove solenoids. (I know, I know - I trust you're sensing a theme here...)
What to do? Well, the first step was finding some kind of wiring diagram. I went to images.google.com and typed in "mercruiser trim pump single solenoid".
Ah, there they were in all their glory! Many drawings featuring single solenoid schemes that we could use to decipher the mystery of the purple wire! The answer was that the purple wire didn't apply to our boat. The purple wire would have been used on a 3-button trim control. We didn't have that due to the age of our boat. We have a momentary switch that returns to the neutral position after being pushed up or pressed down.
I guess the moral of the story is that there IS an answer out there for what ails your boat. You just have to be creative in how you look for the answer. Simply typing in "Mark Twain" and the model number is going to get you a lot of historical photos of riverboats and maybe some old magazine ads. Start breaking down the specifics of what your problem is. For example, our problem was the trim control for a Mercruiser I/O. By using the name as a keyword, I was able to see a LOT more results.
I hope this helps you in your search for answers for what ails your boat!