A couple of years ago the electric start on our 1990 Mercury 25hp outboard stopped working. I’d thought about taking it in to a marina to get it repaired but that would be awkward, put the boat out of commission for an unknown amount of time and likely be costly. It still started well with the manual “pull the rope” method so nothing was done. This year it was the target of a DIY repair.
The predecessor to the Merc 25hp was a Merc 20 hp. One year my dad decided an electric start would be a good idea. Perhaps there was a day when it was a little reluctant to start and there were too many pulls on the cord. I suspect the 20hp model couldn’t be upgraded with electric start so the 25hp was purchased for the grant sum of $2,595.00
The button for the electric start had failed once before so it seemed the logical thing to check first. Sure enough the continuity meter said there was no connection when the button was pressed. A button was ordered, waited for, and eventually made it’s way to the lake and was installed. Nope, still no working electric start. 😕
The next likely culprit is the starter motor. Connecting it directly to the battery produced nothing so I‘m pretty sure it’s broken. I’d previously ruled out the battery itself by charging it up and also substituting in a known good and newer battery. I removed the starter motor and disassemble it to investigate.
The first problem with the starter is that the wire connected to one of the brushes has broken off. In the picture below the copper braid wire and loop hanging off on the right side should be connected to the terminal above.
I solder the wire onto the terminal but I’m not very confident that this repair will hold up to the the demands of the starter but it’s worth a shot.
Problem number 2 is that a piece of the magnet inside the housing has cracked and is just rattling around loose. It’s not too big so perhaps it will still work with a bit less magnetic force.
I reassemble and reinstall the starter motor and no luck, still no working electric start.
Ok, a replacement starter motor is located, thanks to Amazon, ordered, waited for and eventually it makes it’s way to the lake. I install the new starter, push the button and nope, still no working electric start. Power directly to the starter motor proved that the new starter is working.
This is getting a little frustrating. Good thing the Merc is still usable with manual starting.
This pretty much leaves only one component to be the “problem child”, the solenoid.
In the photo above the solenoid is the little black thing with the yellow and red wires connected to it. It’s function is to connect the lower current starter button to close a connection between the higher current yellow and red wires which sent 12V+ to the starter motor. Shorting out the solenoid across the yellow and red wires causes the starter motor to fire up. This test pretty much indicates that the solenoid is not doing it’s job.
So, a solenoid part is located, thanks to Amazon, ordered, waited for, and eventually makes it’s way to the lake and is installed. With great anticipation the button is pressed and … nothing! This is quite disappointing and annoying as I’m pretty sure there is nothing left that has not been checked or replaced with working parts.
What the photo doesn’t show clearly is that there are 4 wires connected to the solenoid and I’ve only connected 3. After connecting the last wire we finally have success!
At this point all the components involved in the electric start system, except the wires themselves, have been replaces. Replaced slowly, over the course of close to two months.
It’s nice to have the electric start working once again and I‘ve learned pretty much everything there is to know about an electric start on a 1990 Mercury 25hp outboard motor.