1972 140 horse mercury outboard

[tony1117]

I recently just bought my first boat and needed some help/suggestions from some people so i decided to post on here so i can hopefully get some help. i don't know a ton about these big motors im use to 9.9 ha...but the owner i bought my boat off of said the motor will run very well but starting the motor is very tough. he said he used starter fluid on it which i know was not a good thing. i was posting this to see if anyone can tell me the best way to clean up the motor or maybe fix the motor so its turn key again..any suggestions will be very appreciated thanks!!

 

[Barnacle_Bill]

Re: 1972 140 horse mercury outboard

First thing to do is get a good manual and start testing. Have you done a compression check? Has the motor sat for any length of time?

 

[monk-monk]

Re: 1972 140 horse mercury outboard

Well you've come to the right place !! First i would get a manual for that motor...read it and learn ! One of the first things i would do is check the internal wiring harness...these old merc motors are notorious for having dry and brittle insulation on the wires...if the wiring harness has cracks in the insulation the voltage can jump from one wire to another resulting in failure of the ignition components. Then you should do a compression check, you need to make sure all is well internally before you go any further. Next would be the fuel system...making sure it is working properly. You will need to learn the annual maintenance for these motors...Check your entire wiring harness, do a compression check, then go from there...if things look good, GET A MANUAL...it is a must !!

 

[tony1117]

Re: 1972 140 horse mercury outboard

First thing to do is get a good manual and start testing. Have you done a compression check? Has the motor sat for any length of time?

ya the motor has been sitting for a few years what exactly is a compression check ive heard that brought up a few times. thanks for help

 

[monk-monk]

Re: 1972 140 horse mercury outboard

The first thing is to examine your wiring harness from the Helm control all the way to the termination points at the engine...you don't want any cracks in the wiring insulation...with that all said...now you can do a compression check...get a "middle of the road" priced compression gauge at a local auto parts store...learn how to use it...the compression check tells it all...if the compression isn't within + or - 10% of all other cylinders, then you are only asking for trouble attempting to put the engine in service...wiring harness so you can crank the motor without "shorting" something out...compression test to see what you have to work with...

 

[waynelk]

Re: 1972 140 horse mercury outboard

I agree on a compression test for a good starting point. The old inline 6 mercury can be a bear to cold start. Pump the squeeze ball till firm, fast idle lever forward, choke on, turn key to start. If starter kicks out, no choke just hit key. Those motors only choke 2 of the 3 carbs and they usually don't close very tight. Never use starting fluid as it removes any lubrication from the engine. Better to use premix in a squeeze bottle. Hard to "flood" these motors. Carbs need to be clean, float level/needle seats good, engine best if all the way down. I made my own "fuel enrichment" with a motorcycle electric fuel pump, to a 1/4 tubing, reduced with a cap tube. When I hit the button for 3 sec. the pump shoots premix into the bottom carb. Starts right up cold. When warm you should be able to tap the key and it should start right up.

 

[CVX20SPRINT]

Re: 1972 140 horse mercury outboard

I spent quite a bit of time this summer getting my 73 150 Merc running good and it does,but I'll tell you there will be some kind of enrichner or primer on it before it hits the water next year.Just this week I read on one of the boat forums that OMC(early 80's) came out with a primer kit and then Merc offered one at some point too.I guess someone figured out that the choke shutters don't do sh*t.I'd truly love to get a look at one.I was seriously thinkin of using a manual hand primer(plunger type pump) like those they used to use on snowmobiles although a small elec. pump would work really well.I have to go to the back to pump the ball so I was just going to mount it in the lower engine cover.Run 1 small line into each carb permanently,pump the ball hard,2-3 pumps of primer,bit of idle lever and it should fire right up instantly.If it starts and stalls then stock choke should do the trick at that point.If not give it another shot of primer.Almost impossible to flood these old L6's.

If I don't find something better I'll have to look closely at the carbs to find a good spot to drill and install the primer lines.

 

[waynelk]

Re: 1972 140 horse mercury outboard

I fed only into the bottom carb with no choke plate. Made a fitting to go from 1/4 inch to cap tube.(Small copper tube) Bent copper tube to go through plastic carb guard on side where throttle butterfly opens. Fast idle opens butterfly, shoot a little premix in, use choke on other 2 if you want.(I didn't. Had fuel pump hooked to choke button.) Fired right up every time.