88 special burning rectifiers

[labrat86]

I have an 89 evinrude 88 spl that keeps burning rectifiers. It charges fine with a new rectifier, but if run at over 2500 rpm for any period of time it begins to overheat the rectifier and it begins to go up to as much as 17-18v and will eventually melt the rectifier. I have run a new tach sending wire outside the harness to eliminate a possible short. This is an unregulated 10 amp charging system with only a rectifier.

 

[petryshyn]

Re: 88 special burning rectifiers

Does this stator have three leads? Is it possible that they have been intermixed? Or maybe more common, the rectifier leads intermixed? Is it also possible that your using a three wire rectifier in a four wire application?

 

[labrat86]

Re: 88 special burning rectifiers

This stator has two leads. The rectifier that I replaced had only three leads. According to my service manual, these are correct. When I installed the new rectifiers they contained a special note that the yellow leads were the same. I have also tried three different batteries, three different tachs (one new), and one new stator. All with the same results.

 

[petryshyn]

Re: 88 special burning rectifiers

Are you getting your voltage readings from the battery using a handheld voltmeter? Or are you measuring the voltage at the rectifier red lead to engine ground?

 

[labrat86]

Re: 88 special burning rectifiers

The voltage was measured at the battery with VOM. If the battery is a little weak, it won't go over voltage. If a battery is fully charged, it will immediately go over voltage. The rectifier still gets hot either way.

 

[petryshyn]

Re: 88 special burning rectifiers

Is it possible that this is a wrong flywheel?I'm not familiar with your engine, but is it possible that the rectifier is designed to be in contact with block and is mounted incorrectly(flipped around, reducing heat transfer to the engine?) Does this model rectifier require a di-electric grease when mounting?<br /> Its easy to reduce the voltage to the battery,(whole other story) but I highly suspect its other issues. If the battery is getting tired(sulphated, causing high internal resistance) it will allow a voltage rise, especially if its an unregulated charging system.(this could damage your accessories) I would check the battery carefully. Just cause its starts the engine, doesn't mean its OK. <br />-flywheel?<br />-mounting of rectifier?<br />-battery's condition?<br /><br />If you're a hobbyist, we could design a reg. for $15.00<br />

 

[labrat86]

Re: 88 special burning rectifiers

The rectifier does not require the dielectric compound. The flywheel is a possibility that I had not thought of before. I had thought of changing over to the rectifier/regulator unit that came out on some of the 88 specials, but I understand it is water cooled and I am not sure that my block has a place to mount it. The regulator might just solve my problems though.

 

[petryshyn]

Re: 88 special burning rectifiers

One more idea....does your charge coil have an adjustable air gap? If so, increase the air gap to reduce output to an acceptable value.<br /> Do you know how to measure current? If we measure the current output from the rectifier red lead at 2500 rpm or higher, we can determine if the coil is actually putting out too much for the rectifier unit.<br />- adjustable air gap?<br />- battery OK?<br />- correct 'rated' rectifier?<br />- correct 'rated' alt. stator?<br />- proper flywheel?<br />- ammeter reading@2500rpm (add a headlight accross batt. when testing current. This will compensate for a tired battery and prevent bogus readings)<br />

 

[clanton]

Re: 88 special burning rectifiers

What is pn of new stator. If you look behind the flywheel under lifting bracket, you should see a plate/cover with 6 bolts, remove this cover and you can install a water cooled regulator.