1987 Evinrude XP150 charging system question.

yello

Recruit
Joined
Jul 15, 2017
Messages
5
Hello all, I have a quick question regarding my 1987 Evinrude 150. Model STLCUR. How does the charging system work on this motor? Does it start charging as soon as the motor starts running? Or does it start charging after the motor has been running for a few minutes / at higher RPMS? I ask this because today i was running my motor on muffs in driveway and checked starting battery. It only reads like 12.6 - 12.8. The battery has never died on me on the water but I was just wondering if something was up with my motor.
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
What does your starting battery normally read..... Engine OFF?..... Engine Running?

The charging system is in effect the instant the engine is running. Look closely under the flywheel at the stator. If the coils are exposed, you have a 35 ampere stator and as such, the charging system also incorporates a water cooled voltage regulator/rectifier assembly.

The stator has two large black coils to the rear portion of it. Are either of them dripping a sticky looking substance down on the powerhead area?

Has your tachometer been acting up lately? The tachometer operates off of the charging system.... any erratic change in its operation is usually due to a failing regulator/rectifier assembly
 

yello

Recruit
Joined
Jul 15, 2017
Messages
5
Hi thanks for the reply. Normally when my engine is off it reads like 12.4 - 12.5 volts. I can see the exposed coils in the stator so it must be the 35 amp. I dont notice anything sticky leaking from the large black coils. My Tach has never worked since I bought this boat maybe 7 years ago. I just thought it was a faulty tach. Would I have to run it at harder RPMS to get the charging system to charge more? Or does it start putting out 13-14volts rite at idle or do RPMS need to be a certain point?
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Hi thanks for the reply. Normally when my engine is off it reads like 12.4 - 12.5 volts. I can see the exposed coils in the stator so it must be the 35 amp. I dont notice anything sticky leaking from the large black coils. My Tach has never worked since I bought this boat maybe 7 years ago. I just thought it was a faulty tach. Would I have to run it at harder RPMS to get the charging system to charge more? Or does it start putting out 13-14volts rite at idle or do RPMS need to be a certain point?

Do the following test ASAP and let me know what you find. No tachometer for seven years huh?... Yeah, could be a bad tachometer OR a case that you've been extremely lucky.

********************
(Testing Tachometer With Water Cooled Regulator/Rectifier)
(J. Reeves)

A quick check is to simply plug in a another new tachometer as a piece of test equipment. If the new tach works properly and the old tach didn't, obviously the old tach is faulty.... but usually boaters don't carry around a spare tach (see below).

A faulty rectifier wouldn't damage the tachometer, the tachometer simply wouldn't work. This is due to the fact that the tachometer operates off of the charging system and the rectifier converts AC voltage to DC voltage, enabling the charging system. A faulty rectifier disables the charging system, and the tachometer simply doesn't register.

However.... those water cooled regulator/rectifiers that are used on the 35 ampere charging systems (and some others) bring into play a different type problem, and as you've probably found out, they are really a pain to troubleshoot via the proper procedure. There's an easier way.

The tachometer sending/receiving setup operates off of the gray wire at the tachometer. That same gray wire exists at the engine wiring harness which is connected to the engine electrical terminal strip. You'll see that there is a gray wire leading from the regulator/rectifier to that terminal strip, and that there is another gray wire attached to it. That other gray wire is the wire leading to the tachometer which is the one you're looking for.

NOTE: For the later models that DO NOT incorporate a wiring terminal strip, splicing into the "Yellow Wire" mentioned will be necessary.

Normally the Gray wire leading from the tachometer is attached at the terminal strip to another Gray wire which leads from the water cooled voltage regulator/rectifier...... remove the gray wire that leads to the tachometer. Now, find the two (2) yellow wires leading from the stator to that terminal strip. Hopefully one of them is either yellow/gray or is connected to a yellow/gray wire at the terminal strip. If so, connect the gray wire you removed previously to that yellow/gray terminal. Start the engine and check the tachometers operation, and if the tachometer operates as it should, then the regulator/rectifier is faulty and will require replacing. If the tachometer is still faulty, replace the tachometer.

If neither of the yellow wires from the stator is yellow/gray, and neither is attached to a yellow/gray wire, then attach that gray tachometer wire to either yellow stator wire, then the other yellow wire, checking the tachometer operation on both connections.

I've found this method to be a quick and efficient way of finding out which component is faulty.... the tachometer or the regulator/rectifier. It sounds drawn out but really only takes a very short time to run through. If the water cooled regulator/rectifier proves to be faulty, don't put off replacing it as they have been known to catch on fire with disastrous consequences.
 
Top