Diagnosing my 92 Mercruiser 5.7 No Start Issue

[UtahBoating]

Good morning -

I would like to get some feedback on my situation. 2 weeks ago brought the boat out and de-winterized it. I kept the battery charged and inside all winter. It fired right up in my driveway. The next day we took it to the lake and drove it around for a few hours. It ran great with no issues.

Towards the end of the day we fired it up and started to head toward the marina and hit a series of large waves and the boat stalled out. (Not sure if this is even related but it is when my issue started). The boat would not start after just turned over and over. It was behaving like it was out of gas. (My gas gauge is broken and drops to empty after the first 1/4 tank is burned - this is on the list to repair this year). After floating for about an hour and trying intermittently to start the boat I could tell we were starting to wear the battery down. We flagged down a boat and they towed us into the marina.

On the way home I stopped and put 5 gallons of gas into the boat. We brought it home and hooked it to the hose and it started up after a couple of attempts. I figured it must have been out of gas.

Fast forward to yesterday - we took the boat up to the lake and stopped and filled it up. It took just under 20 gallons plus the 5 from last week and I figured I was close to 25 gallons. This bothered me because the tank is supposed to hold 30 gallons.

We backed the boat in the water and it would not start. It was cranking over but it sounded weak. Brought the boat home and hooked it to the battery charger. This morning I hooked up the hose and the boat fired right up. I ran it on the hose for about 30 minutes. Turned it off a couple of times and it started right back up.

Heading up to the lake to give it a water test.

So on to the question - will a weak battery cause the engine to not create enough spark to fire even though it is turning over. I have gone over all the connections and could not find any loose wires anywhere including the back of the key.

I am wondering if it really was as simple as running out of gas and I just worked the battery over too hard trying to re-start it or if there is an underlying issue.

Sorry for the long post - just looking for some feedback.

 

[UtahBoating]

Took the boat out today and it ran fine with no issues. Not sure if there is anything wrong or not. Still wondering on the battery.

 

[NHGuy]

Take a look at your volt meter when the boat is running. Key on before start should be 12.6 volts (or therabouts).
Then while the engine is running the volts should be 14.3. If they stay at 12. 6 or less your electrical system isn't charging. If that is the case, once the battery gets low enough the engine won't start even if it cranks.

 

[Crown895]

I would definitely start with the battery. Remember, a 12V battery is considered fully discharged after it reaches 12.6V, like NHGuy says above. A healthy battery should have a charge above that. Don't just charge the battery though. Run it by an auto parts store, and have them load test your battery. Its a hidden thing sometimes when you can charge your battery to its max voltage, but most people don't have access to a load tester, which can really tell you the health of the battery.
Also, it may not be a bad idea to have your carb checked out. Any leaks there or in a fuel hose can cause severe headaches on the water. One really easy thing that I see on some boats around here in north Louisiana, is to have a fuel pressure gauge installed on your fuel line somewhere in your engine bay. With a carb, it will be minimal pressure, unlike EFI, but you'll still know if you have a leak somewhere. Could be useful, and its really easy to do. I'm laughing a little at the fuel gauge thing though. I have an '08 Crownline, and I've had like 3 different fuel gauges in it. They never even last the whole summer. I don't know what that is all about. Just monitor your hours on the engine hour meter, and head for a fuel station every 5 hours of run time and save the $ you'll waste for the new gauge. That seems to work well for me. Good luck!

 

[Crown895]

Oh, and one more possibility, which is probably the most likely. If you had 5 or so gallons of fuel in your tank after last summer, chances are it was not quality gas by the time you de-winterized. Ethanol based fuels like to collect moisture, which may have been the case if you don't have access to ethanol free fuel where you are. Try and keep some Sta-bil on hand if you're not going to use the boat for a while.