I have a key and a button (under the starboard lazrette as well) to start my Yanmar QM. To start I must turn the key (like a car) then push a button to engage the starter. Does anyone else have this set-up as well?

On to the meat of the question. I am noticing a significant voltage drop when engaging the button. It was getting to the point where I could no longer reliably start the engine. On the advice of an experienced technician, I moderated this voltage drop by replacing the in-line fuse holder on the ignition panel and replacing the connector on the solenoid.

This now keeps my post voltage-drop voltage above the 10 volts needed to get the starter moving but I am wondering if this is typical. Anyone else experiencing this voltage drop on start-up? I am wondering if the push button switch is the culprit as the voltage drop seems to happen when I engage this switch. Though I guess it could be the switch or anything downstream from it.

Your battery might be shot. How old? Do you keep it on the charger all the time? It might be cooked.

I second that. Do you place the battery switch on "All" and notice a difference? Also check your return path cable from the engine block to the negative terminal on the battery. A poor connection here will also display a similar problem. You can use jumper cables to test the connection.

Best check on the battery is to get a hydrometer and measure specific gravity of each cell. If maintenance free type, consider taking the battery out and load testing at an auto service center. A weak cell will display the symptoms you are seeing.

The push button switch powers the starting solenoid that engages the drive motor and closes main contacts between the battery and starter motor windings. If the push button switch was shot, the solenoid would chatter or not engage at all. The heavy current to the starter does not flow through the push button. That is not your problem.

The batteries are brand new and were replaced only a couple of weeks ago. Yes putting the battery switch on "both" did help sometimes before the batteries were replaced. The technician made me aware that a bunch of the connections were compromised and I went about correcting the easy ones.

I have an intelligent charger that drops down to a maintenance charge once it finishes the charging cycle so I do leave them charging most of the time. Maybe I should try charging them on alternate weeks in the summer?

I'll check the negative terminals next (easy fix) and the main connections to the switch.

I can easily jump start the engine by shorting out the solenoid with a screwdriver (from the low current post not the heavy current post) and the voltage drop happens only when I push the button. Correct me if I'm wrong but to me this means the problem is somewhere between the button and the solenoid no? Maybe I need to check and replace the button-to-wire connections, run new wire from the button and/or test the button.

All this tinkering makes me wish I took shop class in high school. My supplementary fine arts and language classes are not helping me much here :-)

hmmm, maybe the Solenoid itself is buggered, but you said that changing the connection did fix the problem. Where are you measuring the voltage drop? At the battery terminals?

If i were you, I wouldn't put my batteries on the charger at all in the summer, or only once and a while if you aren't sailing regularly. Especially if they are new. If you are getting out on the boat, the half hour or hour you might run the engine will charge the batteries sufficiently to maintain.

Additionally, you should always start your engine with the batteries on "both" if you need to charge the house battery too. I don't believe our stock battery selectors are the anti-surge type so it is really hard on the alternator to move the switch when running.

I have since discovered that replacing my ignition switch has not resolved my starting issues, and the voltage drop you mention could be a possible reason why as I can often start from the dock the first time but it will not start a subsequent time a few hours later once on the water (unless manually jumped of course)

Did replacing both of the inline fuse holders resolve the issue for ? Did you simply replace with the same size fuses ?

I may have that problem as well.....

I am thinking the solenoid might be my problem…but after reading all of the information in this thread I now have a few other things to check first…..negative lead from the engine block to battery….the batteries themselves (mine are not new and always on an intelligent charger) inline fuses not to mention check all connections as well. Apparently the last owners put a new starter in at least and the ignition is now replaced so at least two things I can cross off the list. Thanks for all of the suggestions….

I am seeing the voltage drop on the voltmeter at the instrument panel at the back of the cockpit. My solenoid looks really shiny so I figured it is probably pretty new... but maybe it's a dud?

My engine starts reliably right now so I'm wondering if the voltage drop is "normal". Still I think I'll hit up my aircraft mechanic friend to check the button and the downstream wiring. There were definitely several factors adding to it to reduce the reliability of the whole system. Removing some of them to keep the voltage hitting the solenoid above 10 volts seems to be the answer. However, I'm just wondering if I should see any voltage drop at all.

I'm used to keeping my batteries on the charger because my old ones were pretty bad. I will try keeping the charger off for a couple of weeks to see how it goes. In general, I am using the engine only a couple of minutes at a time to motor in and out on Wednesday nights. Of course I just used it a bunch this last week cruising in the Gulf Islands.

Lakesailor... what you are describing sounds very similar to what I was experiencing. Check all the connections in the ignition system right down to the connection at the solenoid and see where that gets you.

The inline fuses are common problems - not the fuses but the contacts in the fuse socket. Three years back the one on Rhapsody had a real high resistance connection and burnt the socket. The marine environment is not kind to these critters. I cut the wire and used a butt splice with heat shrink for the replacement fuse socket. I believe Vee Jay had a similar problem and replaced the cartridge fuses with a blade type fuse socket.