Kicker Wiring Question

[Buster_boy]

I have a Sylvan with a 40 horse Johnson. It came that way from the dealer in 2001, so of course it uses the controls and electrical on the helm. I bought a 2006 Mercury 9.9 Bigfoot as a kicker. It came with its own controls. I'll most likely mount those on the side, but how do I do the electrical? How do I get power to the helm for lights and to the Mercury controls at the same time?

 

[Silvertip]

You don't need a steering cable for the kicker. You simply use a kicker link and connect to the big motor and steer from the helm as normal. Throttle and shift cables follow the same path as the big motor. Use an electricians fish tape and push it from front to back or back to front. Attach the cables and pull then through. I don't understand the electrical (lights) issue as the boat should already be wired for nav lights and other stuff.

 

[Buster_boy]

I mean how will I hook up the electric choke/starter? That's currently wired to the Johnson and the pigtail is different for the Mercury.

 

[GA_Boater]

Doesn't the Merc control have a key switch and choke?

It sounds like you want to be able the start and choke the Merc with the Johnson control. It can't be done, you need to keep them completely separate. You will have the Merc harness and cables running to the Merc and leave the Johnson control as it is except for the steering link Silvertip mentioned.

For battery power to the Merc, either use a battery switch wired backwards by hooking up the commons to the battery and the 1-2 to either motor or use two separate batteries, choosing one to power the house side of the boat - I would use the Johnson battery because it's already wired for everything.

 

[Buster_boy]

Yes! That's what I needed to know from both of you. Thanks a ton!

 

[Buster_boy]

So wire the battery to the 1+2, the Johnson to the 1, the Mercury to the 2. I'll need the one key for the lights and stereo, the other key for the Mercury?

 

[Silvertip]

No. Boat electrics are separate from the engine electrics.

 

[ahicks]

For a simple install, I'm not sure why you would want to do anything special for the kicker. Wire it up like you would if it were a stand alone install. Just install the positive and negative leads to the same battery your 40hp is using. No other changes required. From that basic install there are a TON of options you could select from - depending on what you're looking for/need.

 

[Silvertip]

Using the same starting battery for the two engines presents a possible charging issue. The big engine may have a higher output system which could pop some diodes in the smaller engine. Just cautioning you. If the two charging systems are of equal or very close in output this shouldn't be a problem.

 

[Buster_boy]

Well the primary water I'll use this in has a 10 hp limit so I can just disconnect the 40 and use only the 9.9. There is another lake nearby that's unrestricted so I'll switch it back if/when I go there. Or to make it easier, is that where the battery switch comes into play?

Also, if I go stand alone kicker (which by the way makes sense to me now so thanks Ahicks), how do I get my lights and stereo?

I'll do my homework on the alternator output though. Thanks for that FYI Silvertip.

I'm a rookie at all this, can't you tell? lol

 

[ahicks]

Wired as I suggested, you aren't making any changes to the lights and stereo wiring when adding the kicker. They'll continue working as they always have.

Also, the only way those engines could backfeed each others alternators/charging systems (diodes) is if they were both running at the same time - and then I think the chances of damage pretty remote - as long as the battery remains in the circuit.

 

[Buster_boy]

Gotcha makes sense thanks a ton you've lifted some fog

 

[GA_Boater]

If some of the accessories are powered through the Johnson key switch, you could add a master switch to power those items directly from the Johnson battery. Otherwise you would need to turn the Johnson key on just for accessory power.

 

[ahicks]

Easily tested to know if that's an issue. Try turning them on with the key turned off. I'd be surprised if the lights were affected by the ign. switch. My radio wouldn't be wired through the switch, but I suppose that's a personal choice. It could be.

 

[Buster_boy]

Yeah, see I haven't tried anything yet. I bought it with no battery and I don't have one yet either so I have not done anything with it. I know the Merc runs good. I saw it run at the dealer but I have not seen the Johnson run since summer of 2014 but it ran good when I did. Once spring hits I'll have a lot to do. I still have to build a kicker mount, too.

 

[Silvertip]

Wired as I suggested, you aren't making any changes to the lights and stereo wiring when adding the kicker. They'll continue working as they always have.

Also, the only way those engines could backfeed each others alternators/charging systems (diodes) is if they were both running at the same time - and then I think the chances of damage pretty remote - as long as the battery remains in the circuit.

I disagree. One engine will present charging current to the other system. Under normal conditions the diodes in the non-running engine will block that current. However if the reverse current capacity of those diodes is exceeded they can pop. The charging system is not disconnected just because the key is turned off.

 

[sam am I]

At a PIV (peak inverse voltage) exceeding the diode rating -Vr(reverse breakdown max), the reverse current (-i) avalanches going through the roof and smoke the diode/s

So in other words, when the diodes reverse potential difference (Vr) is exceeded, the reverse current (-i) is ONLY then going to be an issue but ONLY when Vr is exceeded. There's no REVERSE current issues until the Vr exceeds the diodes spec.

So given that.......Normally with one engine and one battery, the output rectifier's diodes (the diodes in question when reversed btw for those not following along) normally see's it's max PIV when the engine's charge coil voltage is on it's negative cycle peak and at the highest RPM's when hooked to a fully charged battery of say 14-15VDC. Therefore say (just a ball park, easy spec'ees)

-400Vp......anode/cathode......14VDC

so then -400(Vpeak Coil) - (+15VDC) = -415Vp

Some folks whom claim to be engineers (just wait usually one claims so) knows this of course and these diodes are derated and spec'd out usually at least 150% above these given levels, probably spec'd at -600Vp I'd reckon and for this example.

BTW, The lower the voltage impressed on the output terminals (cathode) the better, from a PIV standpoint that is.........i.e. The PIV is even less (safer) the lower the battery gets.

With two charging systems that are now connected in parallel, the worse case PIV is the same. The worst case PIV the output diodes normally see occurs again when say engine #1 charge coil is on it's negative cycle peak and if engine #2 is running/charging and hooked to the same shared load/battery, it's of course around 14-15VDC again. (Or vice versa, #2 on negative peak and #1 at 14-15VDC). So again -400(Vpeak Coil) - (+15VDC)= -415V

Where the trouble happens usually comes (short of a normally failing rec/reg) is if engine #1 is at this -400Vp and the shared load/battery is somehow disconnected (battery switch mishaps, poor connections, etc) and the regulator of engine #2 is slow to respond to this/a sudden loss of load and spikes up to say +400Vp momentarily (tlr...."time response load regulation" would be critical here, higher quality electronics verses lower), So -400(Vpeak Coil #1) - (+ 400Vpeak Coil #2) = -800V = POOOF!!

OP, you'll be fine hooking up both motor to and sharing the same battery, running or not, fast or slow, engine #1 or #2, 300HP with 9.9HP kicker, makes no difference. The output diodes internal to the rectifier/regulators form a “diode ORing” (Google it) configuration and prevents the systems from fighting each other and "steer the charge currents" allowing sharing of the common loads/battery. Just use the common perko "make before break" battery switch (if you use a switch) and NEVER go into the "OFF" position when the motor/s are running.

BTW^2, Forward current is NOT an issue here either (for those wondering/pondering) as the stator's voltage will drop out(the mags saturate) long before the "if" (current forward max) of the properly spec'd diodes have an issue.


Of course, this is just an opinion and doesn't necessary reflect this station or it's affiliates ....

 

[ahicks]

Wow, that's a long way around to saying about what I said... Thanks for backing my opinion. -Al

 

[ondarvr]

If connecting them to the same battery was an issue, the several thousand boaters (including me) around here that have a kicker with a charging system would be experiencing problems, and we don't.

 

[GA_Boater]

All that is fine in theory, but if either motor has a faulty charging circuit, then what? Very possibly both motors will be making like mini 4th of Julys for a millisecond or 2.

It sure sounds like most are in agreement - Either use a second battery for the kicker or use a switch to electrically isolate the 2 motors.