Control Panel Beeps But Engine Won't Start

[PhilDuhs]

Small drama last week as I had my boat relaunched after a month on the hard to do anti-fouling, etc and went to start the engine to motor out of the marina's travel-lift bay but engine wouldn't start.

My boat has a 2010 Yanmar 4JH4-HTE engine that's in pretty good condition along with the rest of the boat. I've never had any trouble with the engine before - including motoring into the travel-lift bay in January - but last week the following happened:
- 1 click on the start switch I got the normal "beep"
- pressed in further and nothing, no clicks from engine, no drop in voltage, etc

We checked the batteries and no issues there and marina guys were able to start the engine by "hot-wiring it" on the engine itself (I need to learn what they did) so no issue with starter motor either.

What's likely to be the cause? My thoughts:
- control panel itself (although switch works for initial press to get "beep")
- connector on back on panel (I guess I'd still get the "beep" from the panel)
- wiring to engine

Any suggestions or course of action appreciated, especially if someone else's had the same problem!

[JoeRobertJr]

Recommendations:
- Clean the connections on the back of the start button.
- Clean the connections on the starter motor solenoid.

The "hot-wiring" was likely connecting the start solenoid control directly to +12, which is what the button is supposed to do. Hopefully, you just have a dirty connection.

[JoeRobertJr]

Oh, and besides cleaning the connections, make sure they are tight.

[mvweebles]

You probably have a starter relay that looks like the attached - probably what your mechanic jumped across (the two larger lugs 180 degrees apart). Your ignition switch energizes across the two smaller lugs about 90 degrees apart which closes a relay and allows energy to flow to the start solenoid. It's cheap and easy to replace so you may want to start there.

Zhushan Max 300A Continuous Duty... https://www.amazon.com/dp/B09TQP2QRG...p_mob_ap_share

[Island Time O25]

As per long time ago advice of a diesel mechanic buddy, first thing to check are the negative wires somewhere along the line. Just simple tracing of the negative wires for the start system more often than not will lead to the cause.

He explained the science behind looking at the negative first. If the negative is loose the system will not energize at all. But if the negative is solidly attached but the positive is loose the system will work intermittently.

[OldGreyB]

See below attached basic starter schematic and tests.
Use your onboard multimeter set to Volts Dc.