7.4 Horizon intermittant starting problem

Hey All!

Well it wouldn't be a boat if problems didn't pop up now and then... or daily... So over the holiday weekend I ran into an intermittant problem with starting my boat. its a 2001 340DA with 7.4 Horizon, v-drive. most of the time, its normal

- Key on, shifters in neutral, hit start button and away we go.

This weekend everyone once and a while it would either act like it started, hit the button, motor fires up, release button and motor just dies. Some other times I'd hit the button and it won't even turn over.

Figure it could be a couple of things just from some research.
- IAC valve (but that wouldnt' stop it from turning over)
- some relay going bad
- fuel pump ( figure this could be why it starts but immediately dies)
- water in the fuel filter

when it does start, it runs great. no need for extra throttle to keep it going, doesn't die after running a while and coming back to idle.

weird issue to me as I've never had this happen before. any other ideas or places to start?

Thanks!

I would start with a bad or dirty contacts on the Engine rocker start/run switch on dash.

Check the big wire harness plug up on top the motor. It has a hose clamp on it to keep it connected. I had a similar issue and it was the plug coming loose. I loosened the clamp and pushed them back together then retightened.

I had a similar problem on mine last weekend. Turned out to be vapor lock. Google Mercury service bullitin 99-7. Described what happened to me to a T.

Had a similar starting issue which turned out to be a failing starting slave solenoid problem.
Once started it would run perfectly.
Intermittent at the outset and then quit completely and motor refused to start.
Here is a link to possibly solve your issue.
Good luck
https://forums.iboats.com/forum/eng...-troubleshooting-your-engines-starting-system

This happened to me yesterday. Took the boat out to go Fluking. Made my first drift and attempted to start the motor. Well it had other ideas. It started and cut out immediately. I tried three more times and it would crank but no start. I pulled the plug on the IAC valve and plugged it back in. I tried again and it started. I got back to the dock and changed the IAC.
Hope this helps.

As Oceanpearl said- slave solenoid. Had same problem and was guessing so I changed the switch actuator and probably some other stuff because I like to dick around and waste money. But a good mechanic was on the boat to fix something else and knew what it was- i think from hearing/not hearing it (this was a couple years ago so I dont recall exactly). Completely addressed problem.