Trim-Tilt Operation Blows Fuse When Ignition Switch is OFF

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Author Topic:   Trim-Tilt Operation Blows Fuse When Ignition Switch is OFF

nats posted 07-22-2010 08:11 PM ET (US)
I have [a 2006] Mercury 90-HP FOURSTROKE on [a Boston Whaler] 170 [probably a MONTAUK]. If I use the tilt switch on the motor, the main 20-ampere fuse on the engine pops. If I do the same with the key ON, it does not pop. Any ideas?
jimh posted 07-22-2010 08:33 PM ET (US)
The fuse blows when the current drawn through it exceeds its rating. If the fuse blows in one situation and not in another, the current being drawn through the fuse must be different in those two situations.
number9 posted 07-22-2010 11:56 PM ET (US)
With the key on are you using switch on outboard motor cowl or switch at helm?
jimh posted 07-24-2010 10:58 AM ET (US)
Typically the current drawn by the electrical motor in the trim-tilt system is not supplied via the main 20-ampere fuse, but instead the current comes directly from the primary battery connection. When the motor runs the normal current will be about 20-amperes, and the stall current could be as high as 80-amperes.
Typically the current drawn by the relays that control the motor in the trim-tilt system is supplied by two sources: from the remote throttle handle or from local switches on the cowling. When operated from the remote throttle handle, the relay current comes via the main 20-ampere fuse. When operated by the cowling switches, the current also typically comes via the 20-ampere fuse.
The position of the ignition key switch typically has no effect on how the current in the trim-tilt system flows.
Here we have report in which the position of the ignition switch affects the flow of current in the trim-tilt system. This is very unusual. In order to blow the 20-ampere main fuse, we must have too much current flow when the ignition switch is in the OFF position and the trim-tilt relay circuit is energized. The most likely cause of this problem is a fault in the wiring at the ignition switch. Inspect the ignition key switch wiring carefully for signs of any unintended connections or unusual wiring, particularly with the A terminal and the M terminals.
jimh posted 07-24-2010 11:18 AM ET (US)
Also inspect the remote throttle handle and the trim switch wiring there. The movement of the throttle handle may have caused an abrasion of the insulation on the trim circuits.
Is the ignition key switch integral with the remote throttle and shift assembly? Or is it on a separate panel?
nats posted 07-26-2010 09:07 PM ET (US)
It is seperate I will check out the connections. I did add a stereo, I am wondering if I could have done something wrong there, to cause this problem.
jimh posted 07-27-2010 01:28 PM ET (US)
If the onset of the problem with the trim switch operation causing the main engine 20-ampere fuse to blow began after you made modification to the boat wiring to add a new electrical circuit, you should carefully check the modifications you made. Unless some component of the trim and tilt system or the engine ignition key switch system spontaneously and coincidently failed at that same time, your additions or changes to the boat wiring could be causing this problem.
nats posted 07-27-2010 06:10 PM ET (US)
Today I went back to square one. I undid every wire from my stereo, just as it was , tried the tilt and pop the fuse burnt out still. I think it is time for the pros to take a look at this problem. I thank everyone for their ideas and input.
number9 posted 07-27-2010 10:51 PM ET (US)
Again simple question. There are two switches to trim/tilt the motor. The one one the cowling doesn't require the ignition to be on. What switch and when does the fuse blow?
nats posted 07-28-2010 07:19 PM ET (US)
If the key is on the start position, both tilt controls work. But as soon as I turn the key to the off position. The fuse pops, without working any of the controls.
jimh posted 07-28-2010 08:01 PM ET (US)
This is startling news. Why did you think there was some linkage to the trim and tilt system?

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Author	Topic: Trim-Tilt Operation Blows Fuse When Ignition Switch is OFF
nats	posted 07-22-2010 08:11 PM ET (US) I have [a 2006] Mercury 90-HP FOURSTROKE on [a Boston Whaler] 170 [probably a MONTAUK]. If I use the tilt switch on the motor, the main 20-ampere fuse on the engine pops. If I do the same with the key ON, it does not pop. Any ideas?
jimh	posted 07-22-2010 08:33 PM ET (US) The fuse blows when the current drawn through it exceeds its rating. If the fuse blows in one situation and not in another, the current being drawn through the fuse must be different in those two situations.
number9	posted 07-22-2010 11:56 PM ET (US) With the key on are you using switch on outboard motor cowl or switch at helm?
jimh	posted 07-24-2010 10:58 AM ET (US) Typically the current drawn by the electrical motor in the trim-tilt system is not supplied via the main 20-ampere fuse, but instead the current comes directly from the primary battery connection. When the motor runs the normal current will be about 20-amperes, and the stall current could be as high as 80-amperes. Typically the current drawn by the relays that control the motor in the trim-tilt system is supplied by two sources: from the remote throttle handle or from local switches on the cowling. When operated from the remote throttle handle, the relay current comes via the main 20-ampere fuse. When operated by the cowling switches, the current also typically comes via the 20-ampere fuse. The position of the ignition key switch typically has no effect on how the current in the trim-tilt system flows. Here we have report in which the position of the ignition switch affects the flow of current in the trim-tilt system. This is very unusual. In order to blow the 20-ampere main fuse, we must have too much current flow when the ignition switch is in the OFF position and the trim-tilt relay circuit is energized. The most likely cause of this problem is a fault in the wiring at the ignition switch. Inspect the ignition key switch wiring carefully for signs of any unintended connections or unusual wiring, particularly with the A terminal and the M terminals.
jimh	posted 07-24-2010 11:18 AM ET (US) Also inspect the remote throttle handle and the trim switch wiring there. The movement of the throttle handle may have caused an abrasion of the insulation on the trim circuits. Is the ignition key switch integral with the remote throttle and shift assembly? Or is it on a separate panel?
nats	posted 07-26-2010 09:07 PM ET (US) It is seperate I will check out the connections. I did add a stereo, I am wondering if I could have done something wrong there, to cause this problem.
jimh	posted 07-27-2010 01:28 PM ET (US) If the onset of the problem with the trim switch operation causing the main engine 20-ampere fuse to blow began after you made modification to the boat wiring to add a new electrical circuit, you should carefully check the modifications you made. Unless some component of the trim and tilt system or the engine ignition key switch system spontaneously and coincidently failed at that same time, your additions or changes to the boat wiring could be causing this problem.
nats	posted 07-27-2010 06:10 PM ET (US) Today I went back to square one. I undid every wire from my stereo, just as it was , tried the tilt and pop the fuse burnt out still. I think it is time for the pros to take a look at this problem. I thank everyone for their ideas and input.
number9	posted 07-27-2010 10:51 PM ET (US) Again simple question. There are two switches to trim/tilt the motor. The one one the cowling doesn't require the ignition to be on. What switch and when does the fuse blow?
nats	posted 07-28-2010 07:19 PM ET (US) If the key is on the start position, both tilt controls work. But as soon as I turn the key to the off position. The fuse pops, without working any of the controls.
jimh	posted 07-28-2010 08:01 PM ET (US) This is startling news. Why did you think there was some linkage to the trim and tilt system?