‘89 Merc 115 Trim Issue

[Zmerc]

I have an ‘89 Mercury 115 2 stroke 4cyl. Last night the motor flooded and I was trying to get it started before a storm came in. This morning I got the motor to start, turned it off and had no power to re-start. Replaced the inline fuse under the cowl and it started fine, but it would only trim down had no power to trim up. I noticed the left terminal on the rectifier was melted. I have a new rectifier on the way. To my knowledge all the rectifier does is convert AC current into DC. Could a bad rectifier cause power trim to only work one way or is there another solenoid that could be fried somewhere?

 

[richw46]

I have a 95 115 4 cylinder. The hot wire from the battery goes the starter solenoid then jumpers go to each of the trim solenoids. Each solenoid has a relay that closes when you press the trim and that provides power to one of the trim solenoids. Do you hear a click when you press the button to trim up? Does that relay have power? It should have it all the time, like the solenoid.

When you trim down, how does the motor sound? Normal or weak? Trim down is easier because of the weight of the engine. Going up requires (I would think) more power. How is your battery voltage? Can you monitor the voltage when you trim down/up?

The rectifier/voltage regulator gets AC power from the stator and converts it to 12 VDC. On my motor those are the 2 yellow wires that go to the voltage regulator then from there it goes to the battery to charge it as you run down the lake. Power for trim and starting comes from the battery and power from the voltage regulator, when the motor is running, recharges the battery. If the motor is not running your battery could be weak and not raise the engine. Take voltage readings at the solenoids for the heavy wires and the relay wires, when you are pressing the tilt switch

 

[Zmerc]

I have a 95 115 4 cylinder. The hot wire from the battery goes the starter solenoid then jumpers go to each of the trim solenoids. Each solenoid has a relay that closes when you press the trim and that provides power to one of the trim solenoids. Do you hear a click when you press the button to trim up? Does that relay have power? It should have it all the time, like the solenoid.

When you trim down, how does the motor sound? Normal or weak? Trim down is easier because of the weight of the engine. Going up requires (I would think) more power. How is your battery voltage? Can you monitor the voltage when you trim down/up?

The rectifier/voltage regulator gets AC power from the stator and converts it to 12 VDC. On my motor those are the 2 yellow wires that go to the voltage regulator then from there it goes to the battery to charge it as you run down the lake. Power for trim and starting comes from the battery and power from the voltage regulator, when the motor is running, recharges the battery. If the motor is not running your battery could be weak and not raise the engine. Take voltage readings at the solenoids for the heavy wires and the relay wires, when you are pressing the tilt switch

Thank you for the reply. I’m going to get a multimeter today to trace voltage. This morning it trimmed up fine for me to take the motor toter off. Once it popped the fuse it wouldn’t trim up even after replacing fuse. No click or anything it’s just dead. Trim down sounds completely normal. I believe the relay may have gotten toasted from whatever electrical issue caused the fuse to pop, I just assumed it would affect trim down as well. I will read voltage this afternoon and get back with some numbers.

 

[richw46]

Fuse blowing is definitely a problem. The relay may be bad, shorting or just drawing too much current. Mine are isolated from the engine, some kind of non-conducting gasket. I can wiggle it slightly. I've never taken them off. Yours may be worn and allowing a spark to arc to the engine block. You might disconnect the battery, remove the relay and check the condition of the wires, gaskets, etc. Look for anything unusual. Relays are pretty simple. You provide voltage to energize the relay coil and it pushes a pole to close a circuit of higher amperage wire. It's a momentary connection and as soon as you release the button the coil de-energizes and the rod retracts, opening the circuit.

When you take the voltage readings you need to check to see if it's getting ANY voltage and then see how much voltage you're getting when you energize the circuit. You have 2 relays so take readings on both and compare.

 

[Zmerc]

Fuse blowing is definitely a problem. The relay may be bad, shorting or just drawing too much current. Mine are isolated from the engine, some kind of non-conducting gasket. I can wiggle it slightly. I've never taken them off. Yours may be worn and allowing a spark to arc to the engine block. You might disconnect the battery, remove the relay and check the condition of the wires, gaskets, etc. Look for anything unusual. Relays are pretty simple. You provide voltage to energize the relay coil and it pushes a pole to close a circuit of higher amperage wire. It's a momentary connection and as soon as you release the button the coil de-energizes and the rod retracts, opening the circuit.

When you take the voltage readings you need to check to see if it's getting ANY voltage and then see how much voltage you're getting when you energize the circuit. You have 2 relays so take readings on both and compare.

I think the fuse blowing may be related to the bad rectifier. With the rectifier disconnected the fuse doesn’t blow. My trim has 2 solenoids instead of relays. I can jumper the terminals on the solenoid and the motor will trim up, so I would think it’s either the solenoid or the trim button itself. I have a bow trim and a console trim, neither work. My trailering trim has been disconnected since I got the boat. I’m going to swap the solenoids and see If the issue follows the solenoid

 

[richw46]

We may be talking about the same things using different terms. A solenoid and a relay are nearly the same thing. Relays use a solenoid to close a circuit that is high amperage so you don't have to run heavy wires very far. Think about your car horn. Small wires, maybe 16 gauge, in the steering wheel send power to the solenoid inside the relay when you press the horn button. These wires energize the coil by creating a magnetic field that pulls down a connector in the relay that connects 2 terminals of about 10 gauge wire, closing a circuit between the car battery and the horn.

The same is true for your trim (or starter) relay. You press a button (turn the key), it closes a circuit to the relay's solenoid to energize and pull down a connector, closing a circuit of much heavier wires. The trim switch (control switch in the picture) energizes the relays which use coils to close a circuit.

You can remove and test the relay by doing a continuity test between the heavier terminals when you power the lighter terminals. Do not put power on the heavier terminals because that could damage the voltmeter.

I would definitely disconnect the voltage regulator before you possibly damage the stator.