1985 Merc 115 in line 6

[rrumba]

Re: 1985 Merc 115 in line 6

Ok, so i am used to working on car engines that have several timing marks to line up when setting up the timing so that no1 is on a compression stroke to find TDC. This does not seem to have any and i cannot find any in the manual other than to set no1 at TDC. Does it make a difference when or where i am checking no 1 for tDC or just as long as it is at TDC on any stroke at any time?

:Confused:

 

[quicktach]

Re: 1985 Merc 115 in line 6

Sounds like not only are you starving for fuel but you're not advancing fast enough. With all you've done, it is possible you're not doing something accurately. I suggest a real careful link & sync and go through the sequential opening of the idle screws, 1/8 at a time. Is all inter carb linkage OK ? Any wear ?

 

[rrumba]

Re: 1985 Merc 115 in line 6

So today, i checked the carb floats again and corrected them per the post above. Then checked all for good spark again, which was good. Then i sanded down all plug wires then went into the coil packs as well as ensure a good contact was being made. Cleaned off all spark plugs as well.

Used a dial gauge to set no 1 cylinder to TDC and then retarded the piston to .464". Then set the pointer to the 464 mark on the flywheel. Once that was complete, while having someone turning it over and other plugs removed set in the idle position, adjusted the timing to 4*, then put into max throttle and set the timing to 21*

After that adjusted the carbs as noted in the post by Clams Canino. Only able to get the idle to about 800-900 rpms or it would die if any lower. There is no wear in the carb linkages that i can see and i replaced the springs on them when i rebuilt them.

The link and snyc performed tonight was another careful and slow one done. I was able to get it to shift into gear at idle when on the muffs but not sure if that means anything as there is no load on the prop either.

Couple of things.
1. I found a sticker that said "timing mark 6* ATDC", if i tried to set it at 6* ATDC I the pointer would have to move about an inch and there is no possible way for that to happen. Does this really matter since at one time it was actually running?
2. Where the two timing set screws are at between the two halves there feels like a spring that is in there and that it feels very weak. Not sure if there is a spring and how much tension should be on it. Almost seems like it is not being pulled back or have enough tension on it. Does this make any sense?

Tomorrow will be a trip to the water to see how it does with a load on it.

If i am missing anything please chime in. I appreciate the help and patience of everyone.

 

[CharlieB]

Re: 1985 Merc 115 in line 6

It is difficult to adjust both idle speed and idle mixture while on the hose and have them right once on the water, both will have to be reset once in the water and back-pressure is in the exhaust.

 

[rrumba]

Re: 1985 Merc 115 in line 6

Hopefully i will be able to get this done this weekend. Today was Rain Rain Rain. Tomorrow is help with a Veteran function so after that i hope to have some other information.

Thank you guys for your help and patience. It is GREATLY appreciated.

 

[GA_Boater]

Re: 1985 Merc 115 in line 6

Just a question - Would doing the adjustments while running in a barrel have enough exhaust back pressure? Isn't that better than on the hose?

 

[Chris1956]

Re: 1985 Merc 115 in line 6

Rumba, You do know that the idle pickup timing adjustment is to synch the carb opening to the correct timing? The idle stop screw allows the timing to retard below the idle pickup timing. So the motor could idle with timing at 5 or 6 * ATDC, but have 4* ATDC when carbs just start to open.

 

[CharlieB]

Re: 1985 Merc 115 in line 6

Just a question - Would doing the adjustments while running in a barrel have enough exhaust back pressure? Isn't that better than on the hose?

Water level needs to be the same as that with the boat in the water.

Also a fan or a slight breeze to keep exhaust gases from collecting and sucking into the intake.

 

[rrumba]

Re: 1985 Merc 115 in line 6

Just a question - Would doing the adjustments while running in a barrel have enough exhaust back pressure? Isn't that better than on the hose?

the ramp is about 5 minutes from my house so getting to the lake is probably easier right now until traffic picks up, but will keep this in mind.

Rumba, You do know that the idle pickup timing adjustment is to synch the carb opening to the correct timing? The idle stop screw allows the timing to retard below the idle pickup timing. So the motor could idle with timing at 5 or 6 * ATDC, but have 4* ATDC when carbs just start to open.

With 6* atdc that is real close to 464 on the timing mark. I do realize that, but this is getting very frustrating. I set it up so that the carbs are closed with the idle stop adjusted to just make contact with the roller for the carbs.

Now yesterday i put in the water, left on the trailer, and went through the adjustments again. now I was able to get it to go into gear while strapped down and it was about 4K rpms and pushing well, but when i backed off the throttle it instantly dies. now it will not idle and if i feather it in gear, i can get it to come up throttle up. took it off the trailer just to see and it was doing good about 38-40mph at 4k rpms WOT. Tried running it for awhile driving around the lake close to the ramp just in case, and it did well and after awhile again, it would not stay idling, it would die going into gear, acted like it was flooded and could limp back in if i feathered the throttle. Now i can also smell strongly the odor of gas and of course gas leaking out. So back to the drawing boards. seems like the adjustments i was making was about the width of a screwdriver blade but i was able to get her flying for a bit.

This all leads me to believe that i am dealing with nothing more than the carbs and possibly the timing still. My plan is to leave the timing where it sits right now. Go back and do the float adjustments again as i did before with the primary at .04" from needle to lever and .4 from sealing lip to top lever which should be parallel to the top cap. once i am able to get the fuel from leaking then i hope i can get adjustments since it seems as though it is getting to much gas.

One thing i did not replace was the welch plug. i did not remove or clean that area, could this be a probem?

Please let me know other suggestions. i hate not getting this and i do not want to take it to an OB guy but i am close to it now just to be done. Fearing what that cost would be though.

 

[CharlieB]

Re: 1985 Merc 115 in line 6

Idle mixture MUST BE richer than 'Best Idle' adjusted while IN Forward gear IN the water to provide the additional fuel necessary for acceleration.

There MUST BE space between the carb linage and the throttle roller sufficient for the timing to advance BEFORE the carbs open.

Clams posted a procedure on adjusting the stacked 6's, it should be included in one of the 'stickies' at the top of this forum.

All adjustments must be spot on in order for the stacked 6's to really run well, there isn't any other motor that sounds and feels like them.

 

[rrumba]

Re: 1985 Merc 115 in line 6

CharlieB,
Ok, i guess i must have missed or misunderstood parts of it. What you stated makes sense now. Today i will go back and do Clams procedure after the timing portion since i have that all set still. Will update later today hopefully.

 

[rrumba]

Re: 1985 Merc 115 in line 6

So today, went back out to the tower of kick my butt power...........

started off this time by adjusting the carbs to all being open full when full throttle applied and closed when in idle. Checked all timing again as well, still good, then adjusted the linkages for the carbs to ensure that the all was set for WOT and idle and while in idle that the roller for the carbs and the throttle engagement link were just touching.

Next was to check and set the needle valves as well and got everything ready for tomorrow to get it out into the water to try and set the idle and hole shots AGAIN.

 

[rrumba]

Re: 1985 Merc 115 in line 6

nothing new just yet, had to shift gears to get the tow vehicle back up. Hopefully this wekekend.

 

[GA_Boater]

Re: 1985 Merc 115 in line 6

I was hoping for good news. Sidetracked by a duff TV.

 

[rrumba]

Re: 1985 Merc 115 in line 6

Ok folks, the saga continues. I have not had much of a chance to work on this thing due to work, travel and fishing....

I have tried repeatedly to get this right and i do not feel as if i am making any progress.

In DESPERATE need of some help here.

compression is still good for all cylinders. I have adjusted the carbs about 5 more times since my last post. Had it out on the lake and thought i finally made progress on the last time. On the trailer it idled great, hit for a hole shot repeatedly and it ran like it should. take it off the trailer and putter out of the no wake zone and then hit the hole shot and it bogs down then dies. then it would idle but could not put it in gear again without it dying.

Used a timing light on all cylinders to check that there was spark to each wire, which there was, then i noticed that there were about 5 bolts that were backed out completely that held the transfer covers on. Took it to the house, pulled the side plate and checked all bolts, then proceeded to tighten them all up. Now, since this, from my understanding is the holding area for the next charge, is it possible that this might have been the issue or maybe "an" issue or am i chasing my tail on this one?

Should i be checking the switch boxes, i think they were called, stator and trigger instead?


Looking for ANY and ALL suggestion to help make sure i am on the right track.

PLEASE PLEASE PLEASE help. i really do not want to take it in as most of the people i have checked with really are not familiar with the inline 6 merc which really worries me if i need to take it in.

Thanks guys.

 

[CharlieB]

Re: 1985 Merc 115 in line 6

A leaking gaasket ona side cover will make that cyl lose power so it's a good thing you noticed and dealt with it.

It NEVER hurts to check for adequate spark on each cyl,(unless you get too close and it BITES you!!).

Lets get back to the idle mixture. Did you perfect it while ON THE WATER and IN GEAR?

Adjustment on the hose is possible if you have been doing this as long as I have, and even then I rather have it ON THE WATER. I can get very close, but never get it PERFECT as when the motor is IN THE WATER.

Why am I using caps with IN THE WATER? The water column in the mid-leg creates exhaust back-pressure, idle mixture is greatly affected. Having the motor IN GEAR creates load, again greatly affecting idle mixture.

1 1/2 turns out from very LIGHTLY seated should give enough idle fuel to get the motor started and into Forward gear ON THE WATER.

From there very slowly adjust each carb one at a time to achieve the 'Best Idle Speed' possible. Make small adjustments and give plenty of time between adjustments for the motor to burn off any excess fuel and stabilize.

Once at this 'Best Idle' IN GEAR, the motor needs additional idle fuel for crisp acceleration. Almost another 1/8 turn out. Back each out just less than that 1/8 turn and test acceleration. ANY bog, lean miss, cough, or hesitation, in the slightest, is proof the motor needs more fuel, back them out just the width of the screwdriver blade slot and repeat acceleration test.

Repeat to perfection.

 

[Chris1956]

Re: 1985 Merc 115 in line 6

OK, the .464" timing mark is simply for adjusting the timing pointer to read TDC accurately. It has nothing to do with any timing spec. After you have set the timing pointer accurately, forget it exists. Make sure the idle timing spec is exactly as specified, when the carbs begin to open. Make sure the max spark advance (21*BTDC) is dead on as well. Set carb floats accurately. Carb cover leavers should be parallel with carb cover, when inverted. Inspect floats for deterioation and cracking. Set idle mixture screws 1-1/2 turns out from lightly seated. Expect the final setting to be 1-3/4 - 2-1/4 open, but you need a warm motor and an in-the-water adjustment to get it right.

 

[popknot]

Re: 1985 Merc 115 in line 6

This idling issue on these motors seems to be a common problem as I have read several past posts about this. My 1986 115hp is giving me the same issues. Wants to die when put in gear etc. But runs great top end. Also there seems to be some discrepency about primary pick up timing setting as the Seloc manual says 3-5 BTDC or there abouts. The Merc manual in another post I read on this forum says 5-7 ATDC . My mercury manual (downloadable) I got from a Link in a post on this forum says 4-6 BTDC. So i'm not sure where it should be set. your 85 it lists the same 4-6 BTDC. I had the same issues with mine the other day (see post: 115 tower adjustment) thought I finally had it about right. Ran great top end, Good Hole Shot, Was idling around real smooth and nice. Then went to put it back on trailer at ramp and could not power up on trailer had no throttle, just bogged down and died, restarted tried 3 times. Winched it on trailer gave up and went home. Please keep us informed as I would like to hear how this turns out and I think your motor is about the same as mine. Good Luck.

 

[Chris1956]

Re: 1985 Merc 115 in line 6

Pop, the 4-6*BTDC was used on the older distributor, battery powered CDI ignitions. I do not have an OEM manual anymore (Thanks Hurricane Sandy), so I cannot look it up. Sources on the internet put the idle pickup timing at 3-4* BTDC (Clams Canino) to 2* BTDC. Sounds like you are reasonably close.

 

[daveswaves]

Re: 1985 Merc 115 in line 6

it was doing good about 38-40mph at 4k rpms WOT. Tried running it for awhile driving around the lake close to the ramp just in case, and it did well and after awhile again, it would not stay idling, it would die going into gear, acted like it was flooded and could limp back in if i feathered the throttle. Now i can also smell strongly the odor of gas and of course gas leaking out. So back to the drawing boards. seems like the adjustments i was making was about the width of a screwdriver blade but i was able to get her flying for a bit.

4k at WOT is too low, way too low, for this engine. It sounds like you are running too tall a prop (pitch) as well as having difficulty getting the carbs right. It acted like it was flooded since it probably was, If you have not replaced the needle and seat and set up your floats properly you will be chasing your tail. Let us know what pitch prop you are running.