Suzuki DT85 No start and no tilt/trim

[mudcatwilly]

I have a 1990 Suzuki DT85. I fired it up in the driveway last evening to fog the carbs and it started up as it usually does and the tilt/trim was working fine. This morning, I launched at the boat ramp and here's what happened:

Lowered trim into water

Turned key, engine cranked a couple of times, but did not fire all the way (normal for my engine)

Turned key again...nothing. No cranking, no clicks..dead silence. Trim/tilt was dead too. (Battery was fully charged and I switched batteries and got the same result).

Pulled boat out of the water to check wire connections. Everything was connected at the engine and battery.

Jiggled wires just before the controls and all of sudden, I got tilt/trim and I got the motor to crank.

Figured I was good, put it back in the water, tried it again. Again, dead silence when turning the key and tilt/trim was not working. I checked connections again, jiggled wires again...nothing.

I know the battery is good. I don't understand how it was fine yesterday and today, there seems to be no electricity getting to the motor or tilt trim. I would appreciate some thoughts on this.

 

[JB]

Re: Suzuki DT85 No start and no tilt/trim

You have a poor (low resistance) connection in the high current circuit, willy.

Being tight is not enough, the connections must be immaculately clean.

Disconnect them all, including the battery. Clean and reattach. The most likely culprit is where the battery ground cable connects to the engine block.

Good luck.

 

[mudcatwilly]

Re: Suzuki DT85 No start and no tilt/trim

Thanks JB. Do you think that there might be a poor connection within the controls? Mine has the ignition/push key choke on the controls. I will disconnect and reconnect all of the wiring anyway, but I wonder about what the connection is like within the control unit. Why is it that with boats, the connections have to be immaculately clean? Just curious.

 

[JB]

Re: Suzuki DT85 No start and no tilt/trim

The starter motor draws several hundred amps when engaged, Willy. With a +12v source the total resistance in the circuit has to be on the order of milliohms. . .a few thousandths of one ohm. . . and the starter has to provide almost all of the resistance.

Ohm's Law, I=E/R, where I is current in the circuit, E is the applied voltage and R is the total resistance. To get 300 amps with 12V applied, for example, total resistance must be .040 ohms, 40 milliohms, and it must be mostly in the starter motor, not in the wires, connections or solenoid.

In actual practice the starter motor drops 9-10volts, the circuit the other 2-3volts. That means that the rest of the circuit, to drop 2-3 volts, must be less than 10 milliohms. That is far too little to measure with a typical ohmmeter.

This is all in the high current circuit. The currents required by the controls are tiny compared to those two motors and are unlikely to be affected except by a really loose connection. It is the big wires (cables) that carry the high current.

This is true to an even greater extent in automobiles and trucks, but they operate in an entirely different environment.

 

[mudcatwilly]

Re: Suzuki DT85 No start and no tilt/trim

"The most likely culprit is where the battery ground cable connects to the engine block."


Is there supposed to be a cable coming from the battery and attaching to the engine block? Mine does not have that. There are only two cables coming off the battery, one off the positive and one off the negative.

 

[JB]

Re: Suzuki DT85 No start and no tilt/trim

Trace those cables, willy. They end up at the starter solenoid (+ cable) and the engine block (- cable).

 

[mudcatwilly]

Re: Suzuki DT85 No start and no tilt/trim

For what it's worth, the solenoid has some rust on it and looks like the original.

1. Is there a way that I can troubleshoot to see if the solenoid is the problem?

2. Can a bad solenoid cause my tilt/trim not to work?

 

[mudcatwilly]

Re: Suzuki DT85 No start and no tilt/trim

I disconnected the pos(+) cable from the battery. Using a jumper cable, I clipped one end to the pos battery terminal and when I touched the other end to the terminal on the starter, the motor cranked. The key was not in the ignition at this time.

I really need to get my trim up so I can move the boat into my garage. It's stuck in the street right now because the tilt/trim is dead and it's stuck in the down position. Is there a way that I can temporarily power the tilt/trim to raise it, at least until I can fix this electrical problem?

 

[JB]

Re: Suzuki DT85 No start and no tilt/trim

Hmmmmm. If jumping the + to the starter made it crank the problem is in the + cabling. A bad solenoid would not affect the tilt circuitry. Check out the + connection at the battery, then try jumping the + battery connection to the INPUT side of the solenoid. Then try the tilt.

Good luck.

 

[mudcatwilly]

Re: Suzuki DT85 No start and no tilt/trim

Did what you said and connected (+) battery terminal to input side of solenoid. Motor cranked when turning the key and the tilt/trim worked with the key in the "on" position as it normally does. So does that mean that I have a bad cable between the battery and the solenoid?

 

[JB]

Re: Suzuki DT85 No start and no tilt/trim

Yup. I think you nailed it, willy.

Waytogo!

 

[mudcatwilly]

Re: Suzuki DT85 No start and no tilt/trim

I'll change out both the pos and neg cables and post the results. I think it's going to work. Thank you so much for helping me. It's guys like you that make this forum the end-all in boat repair. A stranger helping another stranger without asking anything in return. There are good people left out there. Thanks again.