40 Mariner Magnum - Install Tach?

[Carphuntin_god]

I'm looking at wiring up a tach to monitor the performance of my props.

I've seen the teleflex wiring instructions....but am looking for some kind of instructions/walkthrough/pictures of where I'm actually hooking things up to the motor. (I'm good enough with doing mechanical/electrical stuff...but just not super educated on the setup/parts/etc of the motor). I don't know if I'm tapping wires, or if somewhere on the motor I can just loosen three screws, attach wires and tighten up.

Any links/pointers/pdfs you know of out there?

 

[ricksrster]

Re: 40 Mariner Magnum - Install Tach?

At your remote control there may be a gray wire. This is your tach send wire. IF you dont have the gray wire you can connect a wire from the send post on the back of the tach to either yellow wire on the rectifier at the motor. The rectifier is a small, square box mounted on the engine block. It will have two yellow wires connected to it coming from under the fly wheel. Also there is a red wire that connects to the starter solenoid.The IGN. post on the tach gets connected to the purple wire on the remote control or to the key on post of the ignition switch. The light post on the back of the tach connects to your navigation lights. The Ground post on the tach connects to your ground bus behind your dash or to the neg post of your battery.
http://ww2.tflx.com/PDF/99320.pdf

 

[ricksrster]

Re: 40 Mariner Magnum - Install Tach?

Rectifier:

 

[Carphuntin_god]

Re: 40 Mariner Magnum - Install Tach?

Hmmm... not doing something right

Ok....got things wired up, and I thought working....

When I take off in the boat, things are fine, tach climbs as I'd expect. When i get to around 1/2 throttle ('bout the same point the boat is coming onto plane), and I keep increasing throttle, the tach starts heading back down.

I stopped the motor and tried different pole (3, 4 6) settings on the tach, but the tach still did the same thing.

I'm wired to the post on the rectifier that the grey wire is attached to. Ground is to negative on battery, ign is to positive on battery.

Any ideas what's up?

Do I maybe have to not wire off the battery (even though the instructions seem to say you can/should do that? Do I need to wire to engine somehow for power/ground?

Small red wire on rectifier post with grey wire is the wire I'm sending signal to tach with.

 

[Carphuntin_god]

Re: 40 Mariner Magnum - Install Tach?

Well, tried a different set up. tied into the lines in the starter box. Took power from the purple line (power when the engine is running) ground to black ground, and signal from the grey lead.

Got exactly the same result.

Maybe I'm being dumb here...but...this thing is almost acting more like it's showing "load" than rpm.

When I start turning the throttle, pushing the boat up on plane, the rpms come up. When the boat reaches plane, and I give it more gas, it starts to drop the rpms....If I drop throttle a bit and hit it again, rpms will come up, but then fall again, even though throttle isn't moving.

 

[Carphuntin_god]

Re: 40 Mariner Magnum - Install Tach?

Posting what teleflex told me so that there is note in the forum for others who run into this. I'll have to post my particular findings later after I confirm if this works.


"this is a common symptom when the engine?s rectifier is not operating properly. Attach the gray wire to the ?other? yellow post on the rectifier. If that does not fix it, add a 2000 ohm resistor across SEND and GND post on the back of the tachometer. If it still is not better, replace the rectifier."


I should ask the forum...what else might I notice from a bad rectifier?

Editing post... found a way to test rectifier in this post http://forums.iboats.com/showthread.php?p=1289131#post1289131

 

[j442w30]

Re: 40 Mariner Magnum - Install Tach?

Does it seem like your battery is being charged by the engine? A bad rectifier could cause the battery not to be charged. Are the terminals on the rectifier clean? On mine (I have a 93 Mercury 40 hp) the connections to the rectifier were corroded and one had actually melted some of the plastic on the rectifier. I went ahead and replaced the rectifier (I think it was about $30) and my tach seems to work perfectly. Also, do you have to control box with the separate wiring harness connection for the tachometer and other gauges? Mine had another short harness that stuck out of the box below the main engine harness. I bought the harness that plugs into that and it had power, sender and ground connections for the tachometer and other gauges. Made wiring my instrument panel a breeze.

 

[Carphuntin_god]

Re: 40 Mariner Magnum - Install Tach?

I think my battery charges fine. ( I don't use the boat a ton... but when I check the starter battery, it always seems good).

On my setup, I don't have the harness you're talking about. I think that's on the console models...not the tillers.

 

[Carphuntin_god]

Re: 40 Mariner Magnum - Install Tach?

Well, swapping grey wire on the yellow-wired terminal got it operational.

Now I show 5200-5800 rpm. I think that's a bit high for 5000-5500 WOT throttle I'm supposed to have with this engine. But the boat was unloaded, just me, trolling motor, 1 gas tank in it. 5200 was on plane into the wind, 5800 was on plane with wind at my back.

Have to try a loaded test soon.