50 HP Evinrude Lark, 1972, polarity reversed

[craigvalk]

My friend accidentally reversed his battery connections on a 72 Evinrude Lark, 50 HP twin.<br />I don't have the model/serial for it.<br />However, I believe he has damaged it and wonder if anyone can advise on these symptoms:<br />1. When he shuts it off, the engine now jumps into forward gear. I am sure this is due to a fried blocking diode on the electric shift.. and am also sure this is located in the control box. Can anyone confirm this? And, if someone knows if the diode is still available from OMC that would be great too. I believe there also may be a "shift diode" on this, and am wondering if this is the same thing as the blocking diode or whether it is a separate unit.<br /><br />2. I also suspect he's shot the rectifier for it, I don't believe the alternator is charging, but have not completed metering it out. I don't have the book for this motor, but am familiar with the basic process as I am running a 71 Johnson 60 myself so have done some of these tests. Where is the rectifier located on this motor? Wire colors, and such would be helpful to me. <br /><br />thanks for any advice!!<br /><br />Craig

 

[Drowned Rat]

Re: 50 HP Evinrude Lark, 1972, polarity reversed

Hi Craig. This is a hydro-electric drive model right? If so, then it should jump into forward when shutting the motor off. The L/U requires hydraulic pressure to shift the unit into neutral and reverse. When the motor is not running, you have no hydraulic pressure and the L/U defaults to the forward position. It's a safety feature incase your hydraulic pump fails, you can still get home. The shifter switch should not have been damaged by reversing the wires to your battery. Does the motor still run normally? Still shifts normally when running? It sounds to me like is fine. From what I've heard, these shift switches are no longer available. If it breaks, you have to wire it to an external switch. Hope this helps.

 

[craigvalk]

Re: 50 HP Evinrude Lark, 1972, polarity reversed

Hi DR thanks for that. The boat still runs, yes, but since it is not mine I can't say it never did that "jumping" into gear before.. however, the owner seemed to think it was strange. It is indeed the hydro electric drive, with the push button shift switch. I am more concerned about the charging system, and hope some one can chip in some advice on that!!

 

[DJ]

Re: 50 HP Evinrude Lark, 1972, polarity reversed

Craig,<br /><br />Most likely you did pop your rectifier. They are very sensative to that. The rectifier is not a difficult or expensive repair.

 

[ledgefinder]

Re: 50 HP Evinrude Lark, 1972, polarity reversed

You are correct that hydroelectric shift LUs are not supposed to instantly jump into forward as soon as the ignition key is switched off, and the the blocking diode(s) prevent this. The diodes are on the motor, and are in in two brown rounded objects very aptly nick-named "monkey balls". They are somewhat hidden on the 50, if memory serves, and are under the powerpack towards the back of the motor. I suspect that used diodes from any of the hydroelectric shift motors would work.<br /><br />The rectifier is a round metal can.

 

[Drowned Rat]

Re: 50 HP Evinrude Lark, 1972, polarity reversed

ledgefinder. The hydro-electric L/U requires oil pressure to push the gear into neutral and reverse. When there is no oil pressure, the unit is spring loaded to push it into the forward gear. So, when the motor is off with no oil pressure, you get the forward gear. Supplying power to the solenoids does nothing with the motor off. This is how the manual describes it anyway. I am no expert.

 

[craigvalk]

Re: 50 HP Evinrude Lark, 1972, polarity reversed

Guys.. thanks for the advice all. I found the rectfier for it right here on I boats!<br />Ledgefinder thanks for the location of the diodes, will be back at the lake tomorrow and will locate those and go from there. I think the jumping into gear is more of a nuisance at this point and not critical... will replace that rectifier and go from there.