How do I test a rectifier on a 1988 Mercury 35hp outboard?

Question: It is a small black box approx 1 1/2" square with 3 terminals, the motor does not charge and runs great until battery runs down. I was told by boat mechanic that rectifier was probably the problem but I don't want to buy something I don't need. Thanks

Answer: Make sure the battery is in good condition first, check all wire connections for corrosion. To test the rectifier you will need a VOA meter (Volt Ohm Amp) set VOA on Rx1000 scale. Disconnect rectifier leads (two green leads and one red from the wiring harness connectors and one black lead from engine ground) RECTIFIER TEST are as follows: 1. Place black test lead to green 1 red test lead to green 2 reading should be infinity. Now put the red test lead to red reading should be infinity. now put the red test lead to black you should get continuty. 2. Place black test lead to green 2 red test lead to green 1 should get infinity. place red test lead to red lead should get infinity. Now red test lead the black lead should get continuty. 3. Place black test lead to the red lead place red test lead to green1 should get continuity now go to green2 should get continuty now test the black lead should get continuity. 4. Place black test lead to black lead and the red test lead to green1 should get infinity now place red test lead to green2 should get infinity now test the red lead should get infinity. If any of the VOA meter reading are not obtained replace the rectiefer. NOTE: If your test results turn out exactly reversed, the recifier is good and need not be replaced. Reversed results can occur due to to VOA meter's internal battery polarity. That's it easy yer.

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