CONTINUOUSWAVE

I am having starting problems with my 1985 Evinrude 40hp. I had early season engine troubles which turned out to be the timer base. Have been out a few times since the repair and engine seems to start up fine initially, but after shutting it off for a few minutes or an hour I have had problems starting. When it's a colder start after an hour or so I prime, choke and lift starting lever. This last time I shut engine off for 5 minutes and then it wouldn't start. Only electronics I had running was color chart plotter which shouldn't drain battery in a letter of minutes.

When I check the battery with a multimeter with engine off it comes in at 12.6 volts. Is that a good number for an interstate deep cycle group 29 or should it be higher?

My plotter diagnostic screen says its registering 11.4 volts but multimeter said 12.6. I got this battery in August of the 2012 season.

I am not sure if it's the battery or if the battery isn't charging properly.

When I am on a plane and I check the diagnostic screen on my plotter the voltage ranges anywhere from about 11.4 to 14. I am assuming when it's as high as 14 it is charging.

Someone also mentioned it could be corrosion inside battery cables if they are old and too much resistance. In my research it sounds like this engine needs to really be cranking fast for it to fire properly.

Any tips on diagnosing this concern would be appreciated. I was thinking about just getting a new battery, but 12.6 volts didn't seem to be low to me.

Thanks!

I find that these motors cool down rapidly. When the motor stops all the cooling water drains out. After a really long drift I sometimes need to prime and lift the throttle just as you did. So that is normal. A four year old battery "should" be in good condition but a hydrometer test would be in order. If the battery is sound with no weak cells, then what I would check is the battery cables, starter solenoid, starter, and neutral safety switch. When you say it wouldn't start, what exactly do you mean? It wouldn't turn over? Or it spun but wouldn't fire up?

Please define "wouldn't start." Why do you think the cause is electrical in nature?

What is a plotter "diagnostic screen"?

Since your engine is c.1985, it can't have NMEA-2000. If you read some voltage on a chart plotter, you are probably reading the operating voltage supplied to the chart plotter. This voltage is not the battery voltage. It is some internal voltage in the chart plotter.

Battery state of charge is proportional to terminal voltage. For a chart of how state of charge and terminal voltage are related, see my article in REFERENCE on BATTERY CHARGE at

http://continuouswave.com/whaler/refere ... ttery.html

Battery terminal voltage as a function of state of charge varies with temperature. For around 70-degrees-F, 12.60-Volts corresponds to about 22.5-percent-discharged. What is the accuracy of your DC Voltmeter?

Do you have a mechanical-optical tachometer to measure the cranking speed of rotation? A little 40-HP two-stroke ought to crank-over like a sewing machine--really fast.

Measure the voltage at the cranking motor during cranking and report your findings.

Based on about 50-years of working with battery operated electrical devices, I have a general rule:

If there is a problem with a device that is operated by a battery, the first component to check is the battery.

Engine cranking speed is usually directly proportional to the voltage at the cranking motor. Voltage at the cranking motor is proportional to the voltage at the battery terminals, less any voltage drops in the wiring. For a very detailed summary of all possible electrical connections involved in engine cranking, see my article on this topic in REFERENCE at

ELECTRIC STARTING CIRCUITS
http://continuouswave.com/whaler/refere ... Start.html

To become familiar with the electric starting circuit, read carefully the article linked above. It also offers advice on diagnostic techniques to use in locating causes of problems in electric starting circuits.

Thank you for the replies. The electrical article was very informative.

By wouldn't start I mean that the [flywheel] spins but the engine would not fire.

I will try some battery tests and also measure voltage at cranking motor when cranking. Curious about testing current through battery cables as well. I vaguely recall cutting cables back a few years ago and putting on new leads and noticed some corrosion in the battery cables.

Yesterday I measured voltage at battery when cranking and it did not appear to drop below 12.5 volts which is what it measured initially.

Shut engine off several times while out on the water yesterday for some drift fishing and while docked for extended time for lunch. [The engine] seemed to start up fine. It could be a stronger start, but it wasn't anything like I experienced the last two weekends. Not sure how this condition could have improved by itself.

I will do some tests and report back. Thanks again for the tips!

If the motor spins then your battery and cables are probably fine. If the spark is strong, then that leaves fuel. Pull the spark plugs and hold them against the motor while cranking. Check for a strong healthy blue spark that will jump a good gap. Don't get bit! If OK, then start looking at the fuel system. Does this motor have a choke butterfly or the primer system? I prefer a choke as it is either on or off, no surprises. But the primer can fail in many ways.

If the spark is good, try spraying SeaFoam directly into the carbs. Does the motor start, or cough like it is about to start?
If it starts and continues to run, the problem may be the primer solenoid. If you have electric start, then try to start the motor by turning the manual valve on the primer solenoid to the manual start position. If the motor starts and continues to run when you turn the valve to the manual position, rebuild or replace the primer solenoid.
The alternative is that it does not start with the SeaFoam spray, and that it does not start with the primer solenoid valve in the manual position, the problem may be a lack of fuel to the carburetors, and you may need to rebuild them. If you do that, be sure thoroughly to clean every orifice.

Use an in-line spark tester to verify spark on each cylinder.

To measure voltage drop in a cable use a voltmeter. Connect the voltmeter (+) lead to the end of the cable closest to the battery positive terminal; connect the voltmeter (-) lead to the other end of the cable. While cranking the engine the voltmeter will show the voltage drop in the cable between the two points where the meter leads are connected.