Evinrude 9.9 and fried instruments

[Dave Killen]

I have a 26 foot Thunderbird sailboat which has a 9.9 Evinrude electric start motor with a built in generator. It charges the 12 amp 12 volt Deep Cycle marine battery. The line from the battery has a 30 amp/32 volt fuse. Down line from this fuse is the electric panel switch board through which 12 volt current is sent to various electronic accessories. Each accessory has it’s own switch and is protected by an appropriate fuse. My Horizon DS45 depth sounder is protected by 1 amp fuse.<br /><br />The cir***stances of its damage are as follows:<br /><br />Last week we were starting the motor. The battery was unable to turn it over enough to start it. We pull started it and began our trip from the slip down the water way to the bay where we intended to motor about 3 miles to the Tacoma Yacht club where a race was to take place that morning.<br /><br />About four minutes down the water way the bell on the depth sounder began to ring continuously. Smoke began to emerge from the back of the meter. I shut off its panel switch. When we took it apart we discovered what we later learned to be a diode casing, which had popped off its base and whose insulation was producing the smoke. The depth sounder’s 1 amp fuse had not melted.<br /><br />We continued, as the race course which we expected to run would not involve any shallow waters.<br /><br />As we approached the race course it was apparent that there might be a change in the course so I turned on the VHF, an Uniden MC 625, to check with the race committee. While the LED came on I did not get volume on any channel, including the weather channels. Within a minute I started to get static from the VHF, but it was not the normal sounding static, rather it was very high pitched and more like a whining noise. Less than fifteen seconds later smoke began to emerge from the VHF. I turned it off, and turned off its panel power switch as well. I checked its 6 amp in line power fuse and the fuse was not melted.<br /><br />I opened the VHF’s case and, as in the depth sounder, found what I later learned to be a diode case rolling around on the circuit board, and the accompanying burned insulation.<br /><br />Not knowing the source of these problems I decided to return to my slip while the motor still was functioning.<br /><br />When we got there we discovered that the main fuse from the battery to the electric power panel was open and it had melted under what appeared to be a rather large current load, from the condition of the fuse. None of the other fuses anywhere in the system were blown.<br /><br />The motor’s rectifier is okay. The battery is okay. The motor's stator checks out ok. All the wiring appears clean and there does not appear to be any corosion. The whole system is grounded to the motor. It is not grounded to the keel.<br /><br />Does anyone have any ideas what might have fried the depth sounder and the VHF?

 

[RPBogart]

Re: Evinrude 9.9 and fried instruments

Hi Dave,<br />I think I might have the reason for the problem you described. I had a similar situation last year.<br />Consider the engine running with no battery connected. (This is possible because the ignition system is a magneto and does not require battery power.) As the engine RPM increaces, the output voltage of the alternator will increase, perhaps to several times the normal charging voltage of 14 or 15 volts. Now consider your problem being caused by the battery becoming electrically disconnected from the alternator and still connected to the boat's electrical load, such as the VHF and the sounder. These units might have been supplied with 20 to 50 volts. The fuse did not blow because there was no over current, but the diodes are voltage sensitive and will blow if their maximum voltage rating is exceeded.<br />I would be very careful with the engine connections to the battery. Look for any signs of wire connection looseness or terminal corrosion. That's where I found my problem and the problem has been eliminated for me.<br />One last idea. There is a product that senses over voltage and acts to limit it. Can't remember the name, but I have seen it advertised for boaters with battery switches when turned off while the engine is running will blow the alternator diodes. This might be cheap insurance.<br />Hope this has helped.<br />Good luck.<br /><br />Richard

 

[moorpark]

Re: Evinrude 9.9 and fried instruments

I too have seen this condition occur, only in automotive applications. When the system's battery is either too flat to even take a charge or has been acccidentally disconnected, it's absence causes the charging source (the alternator) which normally is quasi-regulated by the load presented by the battery, to over voltage. The overvolatge oftentimes punches voltage sensitive devices, like diodes in tow way radios, and even instrument panel and headlamps. Always be certain the system's battery is electrically connected and it is a real battery - not one which just looks physically like a battery but whose electrical condition appears to be like it wasn't there, especially to the charging circuit. One of the things I've learned that eats up a battery very quickly would be one of the consumer/marine microprocessor equipped entertainment radios, usually installed as an after market accessory. It draws current whether it is turned on or not, largely to maintain it's channel or station memory. If the battery isn't periodically recharged, which is often the case in marine environments, the battery will go so flat that it won't readily take a recharge for quite some time after a charge current is applied to it, if ever. Better to totally remove any load from your marine batteries if they are going to be left unused for more than a weekend and reprogram the stations when you next use the boat.<br /><br /><br /><br />------------------