Engine Starts without operator input

[zenoahphobic]

I woke up once hearing my Bronco trying to start. I got up thinking someone is trying to steal it, but it was doing it by itself. It appeared my Bronco had a secret night life I didn't know about

It turned out to be water shorting out somewhere setting off the starter relay (can't remember exactly), but was told this is not an uncommon occurrence.

[cpostis]

If it were me, I would not trust the 12 year old relay (if never replaced)! Especially if the relay was closed for a long duration, as in your case. The relay is designed for intermittent use.

You can buy a genuine Yamaha part for about $80, or an aftermarket for about $20. Your choice. I prefer Genuine Yamaha.

Like Townsends, I'd have to know what the guts looked like inside the old relay. If you do replace, could you take apart and send us a pic of the guts? Call me curious! I believe there is a return spring that may have weakened. I'm sure the contacts are pitted to say the least. Never had a starter relay problem with my 15 year old SX150, however reading this thread, I'm going to change mine, disassemble the old, and see what it looks like. I'll send pics as well.

Here's some links on the relay.

ELECTRICAL 2 - Yamaha Outboards - Yamaha Outboard Marine Parts - Yamaha 61A-81941-00-00 - STARTER RELAY ASSY

Starter Solenoid Yamaha 61A 81941 00 00 6E5 81941 11 00 | eBay

[cpostis]

One more thing.

If you are concerned that the problem may have been, and still is an intermittent problem with getting power to your coil on your starter relay when not supposed to, you may wish to try this:

1. Install an agc fuse holder between the bullet connector to the starter relay (brown wire). you can crimp male/female bullet connectors on to the fuse holder leads to do this.
2. install a agc 300 ma glass fuse in the holder (do not vary from the 300 ma fuse rating, as other fuses may not blow)
3. when you trailer your boat, leave the battery connected and switched on

Of course this is not while running your boat, with the switch off, not on or in start position. What will happen is that if you get power (even for an instant) to the starter relay coil the 300 ma fuse will blow (the starter will never engage). Of course you will have to ohm the fuse out to see if it blew or not and remove the fuse/reconnect the starter coil lead before you can start the motor.

This will show you the intermittent problem is still present and further diagnoses is needed. You can shake/disturb wiring throughout the circuit to try to see if you have a short somewhere between. If you do, the fuse will blow as well.

[pstephens46]

Good thought that the engine never actually ran. Very slight wisp of exhaust out the prop could well have been vaporized fuel/oil. There was no smell. I will replace the water pump/housing. Compression for this engine is around 115-120 psi and when last tested was just about where it is now. The fact that the starter solenoid's coil was showing a slight voltage across it with the ignition switch on but not engaged tends me toward a bad switch. Starter motor appears to work well. Might have dodged a bullet. I do shut the batteries off when home but leaving the batteries on and the ignition switch on after I fueled up was probably a mistake.

Any updates here?