Mercury 140hp. Serial number 3424016

[kbh121956]

I'm new to Mercury's. I picked up a 18' StarCraft with this Mercury on it. The control box is missing. Anyway to wire it up so that I can check compression and spark before finding a control box with ignition switch for it? What I have been able to find out is that the outboard is a 1972. Is that correct?

 

[Chris1956]

Sure, simply use jumper cables to connect a starting battery to ground on the engine cowling (see ground bolt), and the battery side of the starter solenoid. Now remove spark plugs, and jumper the starter solenoid.

Alternatively, touch the Positive battery jumper to the starter cable (low on starter) connection to spin the starter. There should be a black wire on the starter (near top). That is the ground. If you touch thta with the positive jumper cable, you will have a fire....

You will need an open end wrench to get the lowest spark plug.

 

[kbh121956]

Chris1956 thanks for your reply. Yes I know how to get her to spin for checking compression. I was wondering how to check for spark. I'm more of a Chrysler/Force person. If this Merc has good compression and spark, I was planning on buying controls for it and keeping it on the boat. I just didn't want to spend the bucks for controls just to find out that the electronics are bad or the compression wasn't up too specs.

 

[merc850]

Do not attempt to check for spark unless you follow this wiring diagram the + and - cables have to be connected to prevent destroying the switchbox and/or rectifier.

 

[jimmbo]

That serial # does check out as a 1972. Keep in mind that the 1972 1400(140hp) uses a different Block, Pistons, and possibly other parts than the 1978 - 81 140hp. Make sure to use the serial # when ordering parts.

 

[kbh121956]

Thanks merc850 and jimmbo. Very nice wiring diagram! Is this Merc to old too invest any money into it? I'll pull the compression first and go from there. Thanks again.

 

[merc850]

Check the lower unit for water and replace the waterpump impeller before running, the plugs should be good - even fouled ones will fire with that ignition system. I have a 1975 850 with Power Trim and it's great!
Parts are available if you look, Mercury has bearings, paint, seals etc.
This is the control box from that era:

 

[kbh121956]

merc850 can you tell me what ignition switch is for this model? I found the control box with the switch removed (missing). It was under the front seats. Also thank you for the help.

 

[merc850]

So you have the box and wiring harness? If I needed a switch I would check with my dealer first for that and a key - I don't know which one you need. The OEM was Indak and they're still in business.

 

[kbh121956]

Yes the box is there split in half with the ignition switch missing. The wiring harness is still in the boat along with the cables. The box looks just like yours. The choke button is also in the box. I would guess that the old fellow (like me) that owned the boat removed the switch as it must have gone bad. He passed away and his darn kids just let the boat sit. Last time it was registered was 2008

 

[kbh121956]

I also found two Mercury keys when I found the box under a bunch of ropes in the front bow seat.

 

[jimmbo]

If the engine hasn't been run since 2008, certain Precautions need to be taken

https://forums.iboats.com/forum/eng...231-awakening-a-sleeping-outboard-by-boatbuoy

 

[kbh121956]

Thanks Jimmbo. Three days ago I used fogging oil on all 6 cylinders. Today I pulled all spark plugs and did a compression check on 5 of them. That bottom number 6 I have no clue on how to do a compression test on it. 1 through 5 all gave me a reading of 144 - 146 pounds. I did not have it set in WOT. There is no sign of the engine block ever being hot as the paint is good. The other day I checked the gear case oil. A small amount of water came out but the oil was still clean. I'll be replacing some seals and the impeller. The plug in where the main harness is, brittle wiring as is the wiring at the control box. Is it available? As stated earlier, I did not put power through the ignition system as the ignition switch is gone. I cranked the engine over my only powering the starter motor. I don't know a lot about Mercury's, I've owned and still do Chrysler and Force outboards. Doing the water pump and gear case will not be hard, very similar to a Mercruiser outdrive and I've owned many of those. Is the compression up to par? Again thanks to all those that have chimed in.

 

[jimmbo]

Number 6 can be a pain. A different Compression Gauge might work better at getting in, the other way is a pain and requires removal of the front and rear cowl supprts, to tilt the pan out of the way(I was replacing the waterjacket cover gasket in this pic, back in 87). The numbers you gave good. before starting it I would spray some gas-oil into the carbs while cranking it with the ignition off and the plugs out, just to ensure the crank, and rod bearings are wet.

 

[kbh121956]

Thank you Jimmbo. I didn't know that the lower pans came off or I would have done it. I assume that the mix is a 50:1 ratio? It will be awhile before I start her up as I will need to replace the engine wiring harness as the wires are in bad shape where they go into the female plug connector. Also I will be replacing the control box along with the main harness that plugs into the engine harness. I really want to keep this outboard on the boat. I can tell that the original owner had put a lot of love into it. After he passed away, his children used the boat as a catchall! It doesn't have a hydraulic tilt on the outboard, it has a electric "Power Tran". I've never seen one before but, It does work! I'll update once I have done the electrical and let the group know.

 

[jimmbo]

To take the lower pan off, the powerhead has to be removed. Power Tran?

 

[kbh121956]

PowrTran. Like this one but, a bigger unit. https://youtu.be/IUXNbL7NkCQ

 

[merc850]

If you have a gage with a rubber hose remove the gage and bend the hose a few times to loosen it up then push it into the plug hole, twist the hose while holding the end in the hole.

 

[Chris1956]

I put a brass elbow on my compression gauge, to check my Merc's compression. Luckily the stem unscrewed from the gauge.