help with 1984 Evinrude 35 hp electric start

[GeorgeN]

This motor has been fine since we purchased it two years ago. We use it in fresh and salt water. It has just started running the start battery down and also showing obvious electrolysis on the motor shaft housing and lower unit. Could an alternator be causing this?

Please advise what I should check and if there are any wiring diagrams and test readings I can use the check this out.

Thanks, George Noctha Santee, CA

 

[bktheking]

Re: help with 1984 Evinrude 35 hp electric start

The two issue probably aren't related. Does the motor have sacrificial anodes installed on the gearcase? If not, the salt water is eating away at the aluminum instead of the anodes.

Battery down- charge it up and put a voltmeter on it, that system should charge up around 14V. If not suspect either rectifier is blown or the stator is shot. Joe Reeves posted a rectifier test , check it first as the stator could be fine, heck it could be a bad battery too.

 

[bktheking]

Re: help with 1984 Evinrude 35 hp electric start

Use the DIODE check function on a multimeter:

Joe Reeves test:

Remove the rectifier wires from the terminal block. Using a ohm meter, connect the black lead of the ohm meter to the rectifier base (ground), then one by one, connect the red lead of the ohm meter to the yellow, yellow/gray,
then the red wire (some rectifiers may also have a fourth yellow/blue wire. If so connect to that also). Now, reverse the ohm meter leads and check those same wires again. You should get a reading in one direction, and none at all in the other direction.

Now, connect the black lead of the ohm meter to the red wire. One by one, connect the red lead of the ohm meter to the yellow, yellow/gray, and if present, the yellow/blue wire. Then reverse the leads, checking the wires again.
Once more, you should get a reading in one direction and none in the other.

Note that the reading obtained from the red rectifier wire will be lower then what is obtained from the other wires.

Any deviation from the "Reading", "No Reading" as above indicates a faulty rectifier. Note that a rectifier will not tolerate reverse polarity.
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[GeorgeN]

Re: help with 1984 Evinrude 35 hp electric start

In regard to the motor having sacrificial anodes..............apparently the former owner removed them when they installed a plastic planing fin on the lower end. We've owned the boat for two years now and did not see any signs of electrolysis that whole time until just recently. That's why I was wondering if the motor had started to leak current somewhere due to faulty rectifier or something. Should it have taken this long for electrolysis to show up in the absense of the sacrificials? We are definitely going to get some zincs on the engine asap. Where can we get some, if you can please advise.

In regard to the battery it is brand new, so I doubt if it is the battery. I will check for 14 volts across the battery while the engine is running. If not I will do the rectifier checks you provided to me. I'll keep you posted, Thanks George Nochta

 

[GeorgeN]

Re: help with 1984 Evinrude 35 hp electric start

I checked voltage across battery with motor running. It is 12 volts whether the motor is running or not. Looks like the rectifier is not putting out. I will be checking the resistance measurements you provided to determine if the rectifier is good or not. If it checks good, I guess we are going to have to check out the stator.

In reference to the sudden appearance of electrolysis on the outboard motor, I also found the corrosion on the aluminum hull in all the scratches an nicks. I checked my ground wire buse for the boat and it is reading a resistance of 5 megohms or so to the boat hull with everything disconnected from the battery.............should be isolated. I think the sudden electrolysis appearance may be due to a ground wire under the floor being damaged possibly causing a stray current condition. We have our wires running under the boat floor where they may be exposed to water in the bilge.............a no no. Please let me know if I'm going in the right direction to getting this problem solved.

Did my outboard ( 1984 35 hp Evinrude ) come with factory installed zinc anode and if so where was it located on the motor?

Thanks, George Santee, CA