Hard starting Merc 115

[Nickolas]

Hi folks,
I recently got an older boat with a 1980 Mercury 115 inline 6. It's been about 3-4 months I guess we have had it and it ran decent when we got it but ran out of steam at full throttle and nearly died. You back off the throttle and you could keep going. Besides that it wasn't too bad as long as you were part throttle. Anyway I recently took all three carbs off and they were so far out of adjustment I don't know how it ran. Two of the three carbs had the needle pretty much all the way in the seat with very little play as not to come out and let fuel in. The third carb not quite as bad but still out of whack. So I have a service manual and made the proper adjustments and that made a world of difference!!! Now I can go full throttle and she screams. Still it was a little rough and cut out at times so I went ahead and did the synchronize job to it and that made it much better.

Only issue now is when it is cold it is a real pain to start. No fuel enrichment valve on this motor just a 2 cover choke system and thats it. The only way I can seem to get it started is to spray a little Deep Creep into the cylinders and she fires right up. If not then it will jst sit there and crank forever not even trying to start. I took the carbs back off and double checked the float settings and it's good. I also rebuilt the fuel pump a month or so back so thats good. Doesn't make any sense to me why this engine is soooo hard to start when it's cold. I have an older Evinrude 85 with only a electric choke and it spins around for 15 seconds or so before it starts but it always starts. The Mercury wont start unless I spray Deep Creep into it. I thought about changing out the plugs to see if that helped any. I noticed the previous owner has 4 L76V and two L78V plugs in it for some strange reason. Motor has 150 psi on all 6 cylinders. So any thoughts on why this thing is so hard to start?

Nickolas

[pointer]

Check you fuel line - make sure all fittings are tight and that the fuel line itself is ethanol resistant.
Trim the engine down to level, pump ball until hard, a little high idle, hit the choke and it should fire up.
Without a little throttle it will be harder to start.
Not sure what the plugs need to be, or why two different plugs were in there.
If your fuel line and connections all pass, check the fuel chucks for leaks - I've had that with the old Mercury chucks.
Sine it'll fire with the deep creep it is starving for fuel and not flooding. Check your idle circuits in your carbs next.

pointer

[Nickolas]

Check you fuel line - make sure all fittings are tight and that the fuel line itself is ethanol resistant.
Trim the engine down to level, pump ball until hard, a little high idle, hit the choke and it should fire up.
Without a little throttle it will be harder to start.
Not sure what the plugs need to be, or why two different plugs were in there.
If your fuel line and connections all pass, check the fuel chucks for leaks - I've had that with the old Mercury chucks.
Sine it'll fire with the deep creep it is starving for fuel and not flooding. Check your idle circuits in your carbs next.

pointer

I think the fuel lines have been on there for quite awhile. I always give it half throttle when trying to start. What are you speaking of a fuel chuck? Yep it is definitely starving for fuel. Doesn't make any sense to me at the moment. Maybe I'll put new fuel lines on and give that a try with some fresh plugs of all the same number.

Nick

[Ira Tindale]

Just became a member on scream and fly but have years of experience on outboards. I used to run an old 1975 150 inline six. It ran great. We also had a time starting it but found if you completely trim the engine all the way down, pump the bulb till its tight then give it a hard squeeze till you overflow the carbs a little, bring the throttle up and turn it over. It should fire up. Another tip is to bring the low speed idle adjustment about a 1/16 of a turn further out from factory spec. Hope this helps. (It calls for NGK BUHW spark plugs)

[pyro]

There's a method to cold starting an inline six Merc--

Trim FULL DOWN. It must be tilted back to get the fuel where it needs to go.
Pump the ball till it's hard, then squeeze the SH** out of it once more to puke some pressurized fuel past the needles and seats. Don't be shy about it. (DO NOT use starting fluid! There's no oil in it) It should start right up.

[Robby321]

You do have a cold start lever on the box, don't you? Choke alone won't work.

Anyway, a LOT of the old Stacks are real cold blooded. My total crank up rebuild is the same. Its not hoses (but new darn sure wouldn't hurt either on yours, but it runs to WOT, so its getting gas.) or plugs. Still hard to fire with gas dripping out the carbs. And the thing is, ya can't see with the wrap on just when the carbs start pouring gas out, plus not the safest way to go..

Now theres a couple ways to solve it. One "Red Green" style way, one the better way. So for you to get to the carbs on starting, guess you are yanking the faceplate, and the wrap. PITA.

You can drill a small hole in the plate that holds the electrics, slightly higher than the bottom carb, run a short piece of gas resistant hose from the plate, down and just into the bottom carb screen, so its just into the carb front. Silicone it good to the plate, as ya don't want it to come loose and suck into the carb, but if tight, I forgot what size I used, probably hard plastic, 1/4".. but a very tight fit through the carb "birdcage", and the plate. Then only need to pull the face plate, and a squirt bottle of TCW/gas mix. Hell of an improvement.

Or, search ebay for a "Fuel Enrichner", know one made for Rudes. Then with some mounting, and tapping into the top carb, and the "balance tube", hooked up to the choke wire, that way we give pretty much instant fire. Click pic full size
..

[Nickolas]

You do have a cold start lever on the box, don't you? Choke alone won't work.

Anyway, a LOT of the old Stacks are real cold blooded. My total crank up rebuild is the same. Its not hoses (but new darn sure wouldn't hurt either on yours, but it runs to WOT, so its getting gas.) or plugs. Still hard to fire with gas dripping out the carbs. And the thing is, ya can't see with the wrap on just when the carbs start pouring gas out, plus not the safest way to go..

Now theres a couple ways to solve it. One "Red Green" style way, one the better way. So for you to get to the carbs on starting, guess you are yanking the faceplate, and the wrap. PITA.

You can drill a small hole in the plate that holds the electrics, slightly higher than the bottom carb, run a short piece of gas resistant hose from the plate, down and just into the bottom carb screen, so its just into the carb front. Silicone it good to the plate, as ya don't want it to come loose and suck into the carb, but if tight, I forgot what size I used, probably hard plastic, 1/4".. but a very tight fit through the carb "birdcage", and the plate. Then only need to pull the face plate, and a squirt bottle of TCW/gas mix. Hell of an improvement.

Or, search ebay for a "Fuel Enrichner", know one made for Rudes. Then with some mounting, and tapping into the top carb, and the "balance tube", hooked up to the choke wire, that way we give pretty much instant fire. Click pic full size
..

I have squeezed the crap out of the primer bulb until gas spewed over and out of the carbs dripping... no help at all. And No I do not have a cold start lever on a box? All I have is to push the key in and the two flappers cover up two of the three carbs and thats it. And No I never use starting fluid but I use Deep Creep instead. It makes for an excellent starting fluid without the worry of washing all of the lube off. Thing is it used to start fairly easy and just all of a sudden it got real difficult to start. It's running the best it ever has since I adjusted the floats and rebuilt the fuel pump but now it doesn't like to start. But after you start it then it's all good. Full throttle runs like a scalded dog so go figure...

[perfmarine1]

I have squeezed the crap out of the primer bulb until gas spewed over and out of the carbs dripping... no help at all. And No I do not have a cold start lever on a box? All I have is to push the key in and the two flappers cover up two of the three carbs and thats it. And No I never use starting fluid but I use Deep Creep instead. It makes for an excellent starting fluid without the worry of washing all of the lube off. Thing is it used to start fairly easy and just all of a sudden it got real difficult to start. It's running the best it ever has since I adjusted the floats and rebuilt the fuel pump but now it doesn't like to start. But after you start it then it's all good. Full throttle runs like a scalded dog so go figure...

There has to be a way to increase throttle in neutral,That is your cold start lever. It will be hard to start with all that fuel and no air. Post a pic of your controll box,we will try to help.Fogging fluid makes a good starting fluid.

[Nickolas]

There has to be a way to increase throttle in neutral,That is your cold start lever. It will be hard to start with all that fuel and no air. Post a pic of your controll box,we will try to help.Fogging fluid makes a good starting fluid.

It is the deluxe box offered by Mercury. You push in the square button for throttle only and move it forward. If you move it all the way forward your engine will flat out scream if and when it does start. I just scanned the pic from the service manual. Anyway I move it all the way forward and then bring it back about half way. So it has me scratching my head at the moment.

[kingsbiship]

I had a hard time also with my '86 inline... I found by pushing in on the key for 10 to 15 sec. before even
trying to start helped! Ign. must be on! Everything else mentioned also had to be done! You can't flood
a cold inline! They feed 2 cyls. with 1 small carb.

[Robby321]

It is the deluxe box offered by Mercury. You push in the square button for throttle only and move it forward. If you move it all the way forward your engine will flat out scream if and when it does start. I just scanned the pic from the service manual. Anyway I move it all the way forward and then bring it back about half way. So it has me scratching my head at the moment.

OK, thats a newer box, so now prob there. Simple push to keep out of gear. Also, the post saying holding in the choke in for many seconds, does zip, that motor. All it does is slam shut two choke butterflys, the top two carbs. And the comment, using Fog Oil?...my many boat motors stall!.. pretty damn fast.

Now, back to square one here. And a few things you all should know..spraying crap in the carbs..(fix the problem first, and explained in my last post)..well, I have a MASTER "Stack" "Frankenmerc Guru" here, close me, built my motor. He knows his stuff, at it decades, as me too. The reason for NEVER using starting fluid/ether..spray, is simple the combustion pressure created. Too damn easy to "get a broken Reed petal"....and then its a total tear down. On using fog oil, never..motor must be running first, and I use Stabil Fog spray,...hard to do all 3 carbs before engine quits. That said, using Deep Creep, well, all that is Naptha, Isopropyl Alcohol, 100%, NO WATER, like the "rubbing alcohol", and most 15% "light Pale oil". Read the MSDS sheet, same as most "magic in a can"..snake oil. BUT, I USE SEAFOAM, AND DEEP CREEP, ..as done right, (DP) a good soak until quits, fire next day after a sit, and sure does "uncook, cooked rings"..just when back in the water under load, you Will get a fouled plug, or 6! Carry spares.
Anyway, I would not use Deep Creep to start, as NOT meet for that. I need to experiment that though, but I also want to get a fire going in the front yard firepit, spray the D/C, try some WD 40, and like said, simple 2 stroke mix, and see combustion "flash points"..as what ya want is a SLOW burn, not a freaking "cherry bomb" going off. And thats a sure case for digging into the motor, to replace "reed petals". And if any here don't understand what said..fire away...(been in the boat all day...way too many beers, out of gas, next pizza and couch ..has my name all over it!

[Ron V]

Are you holding the choke on while cranking, until it starts? I'm not real familiar with the newer inlines but on the older ones a lot of guys make the simple mistake of jabbing the choke, letting go, and then turning the key. You have to hold the choke on while turning the motor over in order to get the choke effect. Sounds like you know what you're doing from the work you've done on it, so I'm not trying to come across as insulting, but thought I'd mention it since nobody else had.

[Nickolas]

Are you holding the choke on while cranking, until it starts? I'm not real familiar with the newer inlines but on the older ones a lot of guys make the simple mistake of jabbing the choke, letting go, and then turning the key. You have to hold the choke on while turning the motor over in order to get the choke effect. Sounds like you know what you're doing from the work you've done on it, so I'm not trying to come across as insulting, but thought I'd mention it since nobody else had.

Yes I hold the key in while cranking the engine. I dont jab it as you say but do hold it as I know how a choke works. Not insulted at all and I have worked on motors all my life. Mainly car motors but outboards over the last several years and it's about all I work on anymore. I usually go back to square one if I have an issue that I didn't have before. I ask myself what did I do before I have this problem or what I did to cause this problem? It never did this until I adjusted the floats and believe me they were REALLY screwed up and out of adjustment bad. The manual is very clear on the adjustments to these with the two levers. I still have my MAC carburetor adjustment tool from working on cars years ago and used that to make precise measurements on the levers for float adjustments so they are right on the money. And when it does run it flat out hauls.... That motor screams at 5800 - 6000 rpm and is smooth as can be..... just doiesn't want to start anymore.

I even took a carb back off and re-checked the float adjustment and it's right where it should be. So I wonder why now it is so hard to start. Before I made the adjustments the carbs always leaked fuel all over the place because of the adjustment out of whack. The float was as high as it could get pretty much so tons of fuel overflowing. Now with the floats in the right position we are having a hard time getting this sucker to fire. It is a fuel issue without a doubt. I use the Deep Creep as all of the stuff on the can says for many uses. Upper cylinder lube and a starting fluid for me. Just a squirt in a few cylinders and she fires right up and growls. So now why isn't any fuel there to start this beast?? Just for the heck of it I am going to replace the plugs and fuel lines and just look it over. After I synchronized it per service manual specs when she starts it runs soooo smooth but just getting it to start..... Anyway sooner or later I will find a solution. I was anxious to see what others had to say about this motor. I appreciate all replies and advice.


Nick

[kingsbiship]

I found by pushing in on the key for 10 to 15 sec. before even
trying to start helped!

Oh yeah... I forgot, I had an enrichener... no choke doors!

[milkdud]

I own restore and run around 9 of these old inline 6's. Every one of mine needs to be primed really hard. I mean really pump the primer bulb and have the cover off when doing this, so you can verify your running gas down the carbs when over priming it. If your not watching gas run down the barrels of your carbs its not gonna start worth a crap. Also you may want to back your idle adjustments out just a tad. My 1500 merc runs best 2 full turns out from stop. The normal 1.5 turns is too lean.

My totally rebuilt 1500 takes a ton of priming to start, then once warm will start just fine each time after with just a bump of the choke. YOU NEED A HIGH IDLE START LEVER. They are invaluable starting a cold 6 and letting them warm up for a few min.

If your sure you do not have the high idle lever then your out of luck. You can tho. Now this is not safe. But you can disable the safety switch to start in gear. I do this on my outboards so I start them in gear and its a lot nicer on the gears when using high pitch speed props. But you have to be safe cause the first time you start it with the lever all the fwd your going to have real issues at the dock.
Conrad

Conrad