Problems with 140 hp Mercury

[blckolds]

I just bought a 1981 thunderbird formula with a 140 hp mercury engine. I had problems when I took it out for the first time. It did not want to start without starting fluid since that is what the old owner was using to crank it over. Also when I was out on the lake it stopped while trolling and after I got it started and ran it at full throttle for 15 minutes it would not respond to the throttle and after a while it stopped and did not want to start back up even with the starting fluid. <br /><br />So my questions are can I get the engine to a point where it does not need starting fluid to start, where can I find the serial number for the engine? and would changing spark plugs help it crank over again. Thanks for the help in advance.

 

[skier]

Re: Problems with 140 hp Mercury

Welcome:<br /><br />I have the same engine (1979). You should never use starting fluid on outboard motors. Depending on what control you have do the following to start.<br /><br />1. pump the primer bulb until firm.<br /><br />2. either push the botton at the bottom of the throttle arm to disengage the gears and push forward to advance throttle / or / pull the throttle lever out and then forward to advance throtle.<br /><br />3. turn key one position and then push in and hold it in and then crank starter until it fires and then let go of the key and slowly bing back the throttle so that the RPM's ate around 1500.<br /><br />4. Kepp it there until it is warm (You will know when cause as it gets warmer the RPM's climb so when you have very little throttle left it is pretty well warm)<br /><br />Please let us know how you make out.<br /><br />Craig

 

[skier]

Re: Problems with 140 hp Mercury

Sorry. The seriel # is on the bracket that attaches to the boat. It is a little metal plate that is on the pivot tube/steering tube.<br /><br />Craig

 

[blckolds]

Re: Problems with 140 hp Mercury

Craig,<br /><br />I really appreciate all the help. I will try that out tonight right after I change the spark plugs, and I will write you how it turned out. I was also wondering if the engine we have is a good one? and how hard should I push it?<br />Thanks again!

 

[blckolds]

Re: Problems with 140 hp Mercury

While I found the right person to ask. I was using 50:1 mix for the oil and gas. Is that the right amount? and is there a certain oil brand that engine runs better on? Thanks

 

[Valv]

Re: Problems with 140 hp Mercury

I have same engine 1978, they are a little hard to start, but as Merc140 says, NEVER USE starting fluid, 2 strokes need oil in gas to lubricate components.<br />Be sure it is not tilted up, in fact set it all the way down. Be sure you squeeze bulb a lot, give it some throttle (but not in gear, use the cold start lever) press choke button and hold it while you crank. If you don't have success, you might want to check compression in each cylinder, if there is one or more way lower than others, you are in for a rebuild.<br />Also check for spark on all cylinders.<br /><br />Spark plugs shouldn't matter much, just clean them, since they are made to take a lot of deposits before they won't fire (because of design).

 

[skier]

Re: Problems with 140 hp Mercury

50:1 is what is required for this engine. I always put just a little bit more oil per tank (16 gal tank and I add enough oil for 1/2 gal). Use QuickSilver oil from Mercury.<br /><br />This is a great motor, the only problem that I know of with the 140 is if the water pump isn't cooling enough the exhaust ports will eat away. Other wise run the **** out of it. They like high RPM's (Above 3000). Mine is at 5800 RPM at WOT. You can tell what is the best cruise speed by listening to the engine. When it sounds like it isn't working real hard and actually gets quieter, then that is your cruise speed. Mine is 4000 - 4200 RPM's.<br /><br />Enjoy your boat/motor and keep it cool and well lubes and you will have it for a long time.<br /><br />Craig

 

[sho305]

Re: Problems with 140 hp Mercury

With my '75 150 and a '76 80hp Merc, I have to do just that. Get the bulb hard, and do it again if it does not start soon, then set the start throttle up and choke it until it starts. I found that if the motor is tilted up some it starts harder as the gas runs out of the carbs unstead of into the motor! In good tune they still start within say 20 seconds or less depending on how long they have sat still.

 

[skier]

Re: Problems with 140 hp Mercury

I have not noticed that my motor was taking any longer to start in a tilted position than in a fully down position. I can't trim my motor all the way down while it is sitting on the trailer cause the motor hits the ground. So everytime I start it on the trailer ot when launching it is never vertical maybe a 15-20 degree angle. Just don't take your hands off the choke or throttle advance (Cold Start Lever) until she fires.<br /><br />Craig

 

[Valv]

Re: Problems with 140 hp Mercury

I used to cuss at mine because it was killing when it was tilted up a lot (very shallow waters) then I rotated the Mercury switch (which is a stupid invention from Merc., a small plastic cylinder with mercury inside, if it's on a steep incline it will kill motor) a little more vertical and...voila' I can almost tilt motor all the way up without problem. Now I have perfectly adjusted so it will kill when water intake pulls out of water (to be safe).<br /><br />I agree, they are a heck of a good motor and they sound great at high rpm.

 

[skier]

Re: Problems with 140 hp Mercury

The reason behind the Mercury Kill Switch was if you hit a submerged object at speed and the engine was kicked up it would kill the engine so that when it came back down the prop wouldn't hit the water and propel the engine through the transom. With the engine dead it will go down nice and easy saving costly boat repairs.<br /><br />Craig

 

[blckolds]

Re: Problems with 140 hp Mercury

I did not have any chance to work on it yesterday but hopefully today it will be running. I had few more questions for you guys. Is it true that an engine that size should not be trolled for long periods of time? and also how fast should that boat travel at full throttle? I know I am asking a lot of questions but one other thing I had a problem with is the speedometer, All the electrical wiring is hooked up right but it refuses to work. Is there another mysterious part that I should look into? Thank you once again for all the input!!

 

[blckolds]

Re: Problems with 140 hp Mercury

Today I was out trying to get the boat to run. After putting in the new spark plugs, cleaning up and fixing the wires I tried starting it but it did not work. I followed the exact directions. It soundd like it wanted to start but no luck. It just cranks over. I checked the fuel lines and fuel is reaching the carburetors. Any feedback I could get on this I would really appreciate it. Thanks!!

 

[Gold Bear]

Re: Problems with 140 hp Mercury

GrandT,<br /><br />I believe you have lost the relationship between "idle ignition timing" and "carb butterfly adjustment".<br /><br />Hook up a timing light to the number one spark plug. With muffs on, spin the engine over and adjust the "idle adjustment" screw until the timing is at 2 to 4 degrees advanced. Tighten the pinch nut on the idle adjustment screw.<br /><br />Look down the throat of the top carb. It should have a tiny gap along the edge of the butterfly, next to the throat body. The distributor has a throttle lever bolted to it. When the distributor is advanced, this lever activates the carb throttle linkage. There are two tiny bolts that hold the distributor lever arm. With the distributor at it's idle position, set the carb butterflys slightly open. In order to access both tiny bolts, un-hook the control cable from the throttle, so you can swing the distributor around to a position that both bolts can be turned.<br /><br /> Adjust the throttle cable so the barrel slips back into it's pocket while the distrubutor is lightly jammed back against the idle stop screw.<br /><br />Once running make a slight adjustment to the idle adjustment screw to get about 800 to 1000 rpms on muffs. Once in the water, you may have to adjust the idle screw again so she doesn't stall when you drop it in gear.<br /><br />Refer to your service manual for more help / guidance.<br /><br />Good luck, Gold Bear

 

[blckolds]

Re: Problems with 140 hp Mercury

I had to rewire to whole boat to get the engine to run but it was worthed it runs perfectly. Barely touching the key turns it over. But lucky me after putting it on the water I came across another problem. <br /> When I first took it out it ran good but as time passed on it started running really bad. At full throttle it would not pass 2500 RPMs. When I ran it on idle for 5-10 minutes and then try speeding up again it does little better but the RPMs would hit 3500 and then rather than getting more power it boggs down and starts to losing power. What could be the cause of this problem? I thought maybe the cylinders are flodded and could be a carburetor adjustment issue but I have not adjusted a carburetor on a boat engine so I don't want to mess with it unless it is my last resort hehe. Thanks in advance once again!

 

[BigWake]

Re: Problems with 140 hp Mercury

I had to rewire to whole boat to get the engine to run but it was worthed it runs perfectly. Barely touching the key turns it over. But lucky me after putting it on the water I came across another problem. <br /> When I first took it out it ran good but as time passed on it started running really bad. At full throttle it would not pass 2500 RPMs. When I ran it on idle for 5-10 minutes and then try speeding up again it does little better but the RPMs would hit 3500 and then rather than getting more power it boggs down and starts to losing power. What could be the cause of this problem? I thought maybe the cylinders are flodded and could be a carburetor adjustment issue but I have not adjusted a carburetor on a boat engine so I don't want to mess with it unless it is my last resort hehe. Thanks in advance once again!

Was this ever figured out for you? OR not to beat a dead horse but i am having the same problem with mine...i have started a thred on it and have got alot of help but was wondering what it was for you?

here is the link to my Thred just incase you wanted to see what i am dealing with.. http://forums.iboats.com/showthread.php?t=269194