mercury 115 inline 6 cyl

[bassgator]

Howdy Folks.
I am the proud owner of (1) 1978 mercury 115 inline 6 cyl SN#4XXXXX parts engine AND (1) 1983 mercury 115 inline 6 cyl SN#14XXXX main/ primary engine that I'm trying to get running. As some posters on this wonderful and helpful forum, I am a new boat owner and would say that my mechanical skills are novice to moderate. Like most, I'm not rich and have decided to try and do this work in the hopes that I can save a few dollars (not going so well so far ;-D) AND HOPEFULLY, learn something about how these "tower of power's" work....so that I can be somewhat confident that I can repair or otherwise unscrew myself if I happen to break down on the water at some future point.

As most have suggested here, I have purchased AND READ the service manual for my motor(s). I have good compression within the 10% tolerances on all 6 cylinders (my dad - car mechanic tested with the gauge prior to purchase) - he actually got the engine to turn over, but it concks out and does not want to idle...he diagnosed as a fuel starvation problem. Upon his diagnosis I replaced the spark plugs (just in case), rebuilt the fuel pump per the service manual with a new kit includign replacing the fuel filter and all the fuel lines leading to it and after it to the carbs.
As a matter of procedure, I have identified that my engines have carburetor type "A" - side bowl & back drag from the manual. I have successfully rebuilt the float cap on carburetor #2 -sticky float needle and broken float spring (carb #1 and #3 seemed to open & close well)..carb #2 was just stuck open and kept visibly flooding with fuel - so I bought the needle kit and rebuilt it. Long story short (too late for that), now the engine does not turn over. I purchased a 1 gallon fuel contaner, new fuel - mixed properly with 2 stroke oil and new primer bulb. I'm hooked up to the muffs with the water on prior to cranking....I'm stumped...could this be electrical? I've read about these things coming with a "kill switch", however, since I am not the original owner and I don't have the user manual for the boat/ controls, I've got no idea where to even begin looking or even what I'm looking for. FYI - the 78 parts motor has a distributor cap...the 83 that I'm rebuilding has the coil(s) if that helps or sheds light on anything.

I'm truly lost and would really appreciate any helpful advise as to how to proceed and I thank you in advance for your attention and or any comments or suggestions...I apologize about the lengthy post.

Best Regards,
Carlos

 

[narvlebenoit]

Re: mercury 115 inline 6 cyl

The black wire with yellow stripe is the kill switch wire .

 

[bassgator]

Re: mercury 115 inline 6 cyl

Thanks Narv...I'll check to see if that is connected or disconnected. Does it sound to you like that's what is maybe going on?

 

[narvlebenoit]

Re: mercury 115 inline 6 cyl

could be lots of things like bad or dirty grounds.Make sure all grounds are clean and tight and a good strong battery to start.

 

[Chris1956]

Re: mercury 115 inline 6 cyl

BG, If the black/yellow wire is grounded there will be no spark.

I presume the motor cranks? There is a troubleshooting proceedure on the CDIElectronics website.

Since you worked on the carbs, did you clean the idle passages? Did you inspect the floats? Orig floats were foam and will disolve. Newer floats crack and leak. Did you set the idle mixture screw to 1-1/2 turns open? That should allow it to start, if you have spark of course.

 

[bassgator]

Re: mercury 115 inline 6 cyl

NV:

Ok...gonna get started on checking the grounds.

Chris:

The motor did crank - turn over when first started at purchase...no controls were connected we just started direct from battery and it didn't idle...it just cranked...my dad gave it some throttle...sounded strong, but wouldn't idle or anything like that...we just killed it from the battery. So...it does crank, just not now. When I turn the key at the controls, I hear the starter trying to crank it and that's it.

I believe that yes I did clean the 2nd carb throughly...I did remove carbs 1 & 3, removed float caps and sprayed/ spot cleaned with solvent...looked to me like carbs 1 & 3 had been serviced/ rebuilt recently, judging by the cindition of the gaskets & the relative ease of which the fasteners came out y'know. I did not replace the floats in these carbs, but did inspect them and didn't find anything wrong (to my untrained eyes)...they looked intact and the springs looked alright as well.

I didn't mess with any of the existing idle mixture settings...I'll get on that and post a follow up.

Thanks for the replies & help guys...at least I feel like I've got some direction and I appreciate that alot. Also I'm going to read up on the wiring in the service manual and see if maybe we didn't connect the controls up correctly....my harness has 5 wires...red, black, yellow with red, black with yellow & gray...basically we connected the red, black and yellow with red line up...did not connect -what I know now is the kill - (black with yellow) and the grey....maybe something's not getting power?

Best Regards,
Carlos

 

[bassgator]

Re: mercury 115 inline 6 cyl

Fascinating stuff guys...I've located the "blackbox" on the cowling support...3 wires - red, black & white...it's the unserviceable type...I'm going to read on in the manual and see how to determine if it is functioning or not....I probably won't be able to test it because I don't have the tools, but my father does.

BTW....Chris...re-read your post...I replaced carb #2 float with a new one, carbs #1 & 3 I left alone...all the floats are the hollow plastic type and I did not observe any signs of cracking or irregularity in the spring.

That's why I suspect something electronic because they do get gas and after I did my light cleanup and fuel pump rebuild...they aren't flooding. cranking motor is working, just no turnover....am I correct in assuming that if I have all 3 spark, fuel & compression, this thing should start right up...might run like crap, but should turn over?

Additionally, thanks for the CDI website tip....checked it out and that's what I was looking for when I found the blackbox.

Thanks again for all the help so far guys...I'm sorry I'm not much more of a mechanic...I'm poking around it pretty good though.

Would some pictures help you guys a bit more? If so, I'll take them...anything that might make this easier for y'all.

TY
Carlos

 

[mr 88]

Re: mercury 115 inline 6 cyl

I would change the impeller before I try to start it. Many times the wiring harness at the connection point on the side of the motor has to be cleaned and the male ends spread slightly to insure good contact.Check for voltage at starter and back track from there.If you put 12 volts to the starter motor and it turned over like you said then you can rule the starter itself out.Link N sync will have to be done,once you remove the carbs in most cases this is the next step.They like to be given a lot of fuel at start up,so once you pump the bulb hard,give it a few more small squeezes and choke her.

 

[Maxz695]

Re: mercury 115 inline 6 cyl

You should never remove the battery cables when the engine is running it could kill your switchboxes (Use the choke to kill it). Choke is the most important thing when turning the engine over as well a proper carb mixture adjustments starting at 1 1/4 turns out from a light seat. The bulb may have to be pumped several times in getting the engine to fire. Once you here it want to fire cloe the choke and increase the lever for throttle a bit then pump the bulb and turn it over. This process may have to be done several times to get it to start. After starting we can go from there good luck.

 

[CharlieB]

Re: mercury 115 inline 6 cyl

Spark must be able to jump a 7/16 inch gap in free air. Make sure you have a hot blue arc on each plug wire.

The stacked 6's LOVE fuel on a cold start, you have to stay ON the choke til it fires, then let go but be ready to puch the choke again if it falters and threatens to die.

You can always fill an squirt bottle with pre-mix fuel and give each carb throat a couple of shots to assist in starting.

Cranking speed is important. CLEAN, TIGHT cable connections at both ends, including the starter/solenoid cable.

Use your trusty jumper cables and jump directly from the battery to the starter, if it cranks faster than using the key, suspect the solenoid has poor contacts.

 

[bassgator]

Re: mercury 115 inline 6 cyl

Mr 88:

Thanks for the info....good to know. I checked the harness...mine connects at the cowel support...the 78 parts motor has the side connect as you described. My linkage to the carbs is the (3) part type - (if this is what you mean), I didn't disassemle the carbs completely...my linkage is exactly the same as it was when I bought the outboard...I did not remove any of these portions as I only removed the carb body itself from the block and then the float caps to inspect each carb.

Max:

Good to know as well about the battery...I did not know that and apparently, neither did the gentleman I purchased the used outboard from ;-D. I don't suspect that there was any damage done to the switchboxes...the connections & grounds look goos and the wiring matched exactly as the manual suggests...green, green/white and gree/red..with blacks as they show.

Now...you raise a really good point about the choke. From the manual diagram I see that the choke lead wire is yellow/black and it is my understanding that I should hear the choke solenoid? click when I attempt to start....I believe that my yellow/black wire is one of the wires that is NOT connected to controls...lol...I bet that I've been trying to start this thing with the enricher disconnected and that could explain my problem....I guess I should explain...the boat came with the 78 outboard and its corresponding harness & controls. The 83 motor that I'm working on is a replacement motor, but DID NOT come with the controls....soooooo....I'm using an 83 motor with 78 control....I bet I have it wired incorrectly from the controls....specifically, I'm betting my choke/enricher isn't connected. If that's the case, my new problem is that the wiring diagrams for the controls in the service manual are "spotty" and I'm not sure what wires from the harness to connect to the controls.....PLUS....my throttle lever had a hairline crack in it when I purchased the motor and has finally just broken off...I purchased a new on from ebay and it should be here by wednesday. My guess is that this part was damaged either by the previous owner during removal or by me during transport to my home...regardless...it's important and needed to be addressed...glad it broke now rather than on the water y'know.
I was thinking that if my theory about the electric choke not being connected is correct, I could just splice that yellow/black wire to the yellow/ red wire on my controls?

thoughts & suggestions welcome
Best Regards,
Carlos

 

[bassgator]

Re: mercury 115 inline 6 cyl

Charlie:

Thanks for the reply to my plea for help and useful information. That's what my dad did when he got it to start...he muffled carb 1 with a fuel soaked rag and then gave it some throttle while in neutral while the engine was connected to a battery on an engine stand. That's a pretty neat trick with the jumper cables...I wouldn't have thought of that. I suspect that the starter is ok...I suspect that the engine is actually in decent/ serviceable mechanical order...It feels like it's mostly there and is probably something stupid that I did like....not connecting it up correctly or something. The reason I think that is because the wiring looks good and I found evidence that the upper & lower carb had been serviced recently....the fuel lines are another issue...those have been replaced since, as well as the spark plugs and I rebuilt the fuel pump as a matter of procedure...figured it was best to rule out the basics before really getting into it.

Best Reagrds,
Carlos

 

[Maxz695]

Re: mercury 115 inline 6 cyl

There should be a manual choke nob at leat on my 70 HP it does Yes the black and yellow wire conneced t to the choke solenoind but be sure to push the plunger all the way up inside of the solinoid to be sure it,s free and close enough for the magneto connection to occur. Ater removing my carbs If I do not push the plunger up in the soeniod it will not click. There also should be some kind of choke linkage connected to the carbs that you can lift with your finger to choke the engine.

 

[buzzm19]

Re: mercury 115 inline 6 cyl

I did the opposite, newer throttle control to older merc. the black wire with yellow stripe goes to the orange wire, so your black wire with yellow stripe goes to your throttle control so that when you turn the key off it grounds out the system. Buz