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So now that the weather has turned colder, my 1986 Mercury 75hp has a difficult time starting....more than usual. In this last month I've gone to start it and a few times it has ground down the battery while doing so. I've then charged up the battery and the engine turns right over. It happened again today when I went to pull the boat out for the season. This morning it would not turn over and I killed the battery (although I had it running yesterday). I put the charger on it, came back after lunch to see a full charge. Removed the charger, put cables back on and she started on the first turn.

Ideas? Should I get a new battery for next season? This one has been with the boat for 4 seasons. It sometimes has a difficult time starting in the warm weather too, not like this though...may take a 2-3 tries to start, but does usually kick over.

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4 years is usually enough for a marine battery.

I would buy a new battery at the start of the new season next year.

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Clean and retighten your battery cable connections at the engine and the battery/switch.

You may also have a parasitic drain.

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Thanks Joe and Phil.

Still curious if the level of battery charge makes a difference in how quickly the engine turns over? I have always thought that the fuel/carb system was more integral in the turning over process. As long as the battery was "good" (and the starter) that's all it needed to do, produce enough power/spark to click it over. I'm no engine guy, just basic knowledge...obviously. ;)

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You should have done a low long full charge, which will really fully charge the battery. Marine batteries aren't like car batteries, nor are boat charging systems.

Regardless, that battery is at the end of it's useful life on a boat. It would be fine on a tractor or something you don't mind jump starting.

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Also take the battery out and store it inside if possible (out of freezing weather) You can always have your battery checked, but deep cycle (most marine batteries) need slow long charging at low amperage.
I always stored my marine batteries off the boats and used a trickle charger starting a couple of weeks before the season started again, this would give me a 5-8 year life.

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After fully charging the battery have it load tested by your local marina or automotive store.

Batteries lose capacity over time. As the battery ages an increasing fraction of lead becomes tied up in the lead sulphate form rendering less plate material (lead/lead oxide) available to react with the sulphuric acid. An old battery can "take a full charge" and the battery voltage will seem fine...until placed under load. Load testing tells the true story of the condition of the battery.

Also, if you have power available at your boat slip use a good battery maintainer: BatteryMINDer and Battery Tender are the best: http://www.batteryweb.com/batterymind...arison.cfm. BatteryMINDer also makes a solar version.

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Thanks all. I am planning on a new battery for next season. But still curious, when I do have a nice fresh new battery, will my motor be prone to starting easier?

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If the engine is turning over normally and the engine is hard to start a new battery isn't going to solve that. I'm not going up and read everything here but I got the impression your battery got weak fast after a quick charge, which is a sign of a battery on the way out. A slow full charge just buys you some extra time, so a new battery is the cure, but not for everything.

If you think your starting procedure leaves something to be desired explain what you do exactly.

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A fully charged battery will spin the motor sufficiently fast to draw in and compress the fuel-air mixture for ignition. If you have fuel and air entering the cylinder at the correct time and ratio, the spark plug firing at the correct point of compression, the engine will run.

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Are you making sure the fuel primer ball is hard before starting?

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What is your point?

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Going back to my earlier post, I found it interesting that the engine would not start and in that process of trying to turn over, the battery died. I trickle-charged the battery until the charger showed "full charge". Removed charger, re-attached all battery cables, turn key once, voila! Starts right away nice and smooth. Wondering why that is, is all.

Again, it's an old motor, during the warmer months it takes a minute to start but always does. When it got colder, it took longer to turn over. I always check the primer bulb and have used the same process for a few years, usually starts with out a major hitch.

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My point is to answer this question poster by the originator of this thread, "Thanks all. I am planning on a new battery for next season. But still curious, when I do have a nice fresh new battery, will my motor be prone to starting easier?". Maybe I should have said it more simply, so... A new fully charged battery will spin the engine at a speed sufficient for it to start, however, that is not all that is required. Sufficient fuel and air, in the correct ratio, must enter the cylinder at the appropriate time. The spark plug must fire at the right time. if the spark timing or the fuel air ratio is off or missing, a new fresh battery will not start the engine but it will spin it sufficiently.

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Have the battery load tested. If it tests good you know you have another problem and you saved yourself some money. If it tests bad replace it and see if your problem goes away. If it doesn't you know there is an additional problem. If so the next place I would look is fuel: Carbs dirty or need rebuild? Fuel pump working or need rebuild? After that I would look at spark.

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Along with the components of the motor being dialed in, over choking will flood the motor and create the need to keep spinning the motor. An interesting fact about batteries is that the charge within works through osmosis. When starting, you use the upper portion of the charge. When that charge loses the ability to spin the motor. The longer you wait before trying again, allows the charge to distribute throughout the battery (high density on bottom, low density on top) and you could get another chance to start. The old adage "...wait a while and the battery charges itself..." has some truth to it, kinda.

Garris