1985 Merc 115? falls on its butt

[Bill73x]

Hi all great forum....
I just bought an 87 Starline fish/ski. The s/n on the merc is 6630546. The searching I've done narrows it down to an 85,I could be wrong. It starts fine,idles well. When you give any more than 1/3 throttle it actually loses power but acts like it "wants" to run. sputters and surges. The guy I bought it from thought the "High speed needle" was stuck. Does that make any sense? If so what are some things I can try as we have no mechanics with-in 1 1/2 hours from here. First boat. Thanx Bill

 

[tashasdaddy]

Re: 1985 Merc 115? falls on its butt

go to grubbs.com order a manual for your motor. check the compression on all cylinders with all the plugs out. check spark on all cylinders, i think 90% of the problem is clogged, dirty, gummy carbs. when you get the manual , order rebuilt kits for the carbs, thouroghly clean and rebuild the carbs.

 

[Bill73x]

Re: 1985 Merc 115? falls on its butt

It has plugs that dont look like normal plugs,no gap. How would I check the spark? The guy told me he used a bottle of "Quiksilver"oil in every 6 gallons,does that sound right? I've worked on cars alot and I build and work on a Harley.I can work on it ,just am not at all familiar with outboards. Can someone else check for model year to be sure before I order a manual? Thank you for the reply.

 

[duff]

Re: 1985 Merc 115? falls on its butt

the right amount of oil should be 50:1 and you find the OZ of oil by taking the # of gallons gas X 128= ### then divide that by 50 if you want 25:1 then you divide it by 25

6X128= 768/50= 15.36 oz of oil for 6 gallons of gas.

as for checking spark i got a spark tester at the local auto parts store it goes inline with the spark plug wires and the pulg its self. this way you can check it one cyl at a time by yourself.

duff

 

[Bill73x]

Re: 1985 Merc 115? falls on its butt

go to grubbs.com order a manual for your motor. check the compression on all cylinders with all the plugs out. check spark on all cylinders, i think 90% of the problem is clogged, dirty, gummy carbs. when you get the manual , order rebuilt kits for the carbs, thouroghly clean and rebuild the carbs.

grubbs.com is a Chrysler dealership.:^

 

[Bill73x]

Re: 1985 Merc 115? falls on its butt

the right amount of oil should be 50:1 and you find the OZ of oil by taking the # of gallons gas X 128= ### then divide that by 50 if you want 25:1 then you divide it by 25

6X128= 768/50= 15.36 oz of oil for 6 gallons of gas.

as for checking spark i got a spark tester at the local auto parts store it goes inline with the spark plug wires and the pulg its self. this way you can check it one cyl at a time by yourself.

duff

gotcha,thank you duff

 

[duff]

Re: 1985 Merc 115? falls on its butt

no problem i had the same question and had messed mine up with too much oil. good luck keep us posted

 

[studlymandingo]

Re: 1985 Merc 115? falls on its butt

The spark-gap tester is a must. From what you are describing, it sounds like you might have a cylinder that is not firing as it should. Could be a number of things that would cause this; first thing to do is to is verify your spark.

Have you tried squeezing the bulb while you are underway?

 

[Bill73x]

Re: 1985 Merc 115? falls on its butt

I have'nt tryed that. For some reason I get the idea that is flooding itself out,but alot of fuel seems to be in the bottom of the motor casing. When I lower the motor in the water, alot of fuel is floating on the water. This is my first boat so,I'm not sure what is normal.

 

[jimmbo]

Re: 1985 Merc 115? falls on its butt

Get an atomizer, fill it with a 50:1 gas/oil mix. Withthe cowl off run the engine when it does its sputter surge spray some fuel into a carb, it runs worse that carb is probably fine, if the engine smooths out then you know that carb has a lean condition, most likely gum and varnish, but it might be a leaned out idle mix screw or a sticky float.

If fuel squirts out of the carb vents went running or when you squeeze the primer bulb then you have floats that are stuck in the bowl, a bad float needle and seat or dirt in the needle and seat

 

[studlymandingo]

Re: 1985 Merc 115? falls on its butt

Lot of fuel in the cowl? Do you know where it is coming from? It could be coming from the carbs which could indicate a sticking float, still the spark gap tester is a low budget investment and you will certainly need it at some point.

 

[Bill73x]

Re: 1985 Merc 115? falls on its butt

The fuel is dripping from the bottom of the carbs. What are the odds though that all 3 are sticking. I forgot to mention it sat all last year. I need to verify that it is an 85.
sn# 6630546 , so that I can order a manual.

 

[Bill73x]

Re: 1985 Merc 115? falls on its butt

I just read the "1977 Mercury 150 fuel problem?" post. My symptoms are similar to his,but,I never do get it to"go". I read the link that Tashasdaddy left there about syncing the carbs,but I dont have enough knowledge about outboards to try this. I'm not even sure which screw is the mixture screw and which one is the idle scews. Sad huh?

 

[Bill73x]

Re: 1985 Merc 115? falls on its butt

I need to try to clean float bowls I guess.

 

[tashasdaddy]

Re: 1985 Merc 115? falls on its butt

here's your engine id

http://www.marinepartsman.com/Mercury-outboard-manuals_1.html

115 (6 CYL.) 6436123 AND UP $71.50 $18.50 $22.50 278

 

[Squire]

Re: 1985 Merc 115? falls on its butt

My suggestion is to follow jimmbo's lead. I had a similar problem, rebuilt carbs, rebuilt fuel pump, new plastic gas tank, proper 50:1 fuel mixture and still experienced same symptoms. Would only rev to 1600-1800 rpm and die off. If I timed hitting the choke(push in the key) for a second just before it died it would pick up and run wide open again. I can't remember the person from i-boats who provided my solution as it was over two years ago but i'll try to repeat it. This trial must be done on the water not on the muffs. Check that your idle mixture screws are about one-and-a-half turns out(counter-clockwise) from the all the way in position. Your idle mixture screws are on each carb, your idle adjustment is on your throttle linkage and may need to be adjusted after tweaking your idle mixture - best to keep your idle under 900 rpms for your lower unit's sake. Start by turning the top carb's mix screw out about one eight of a turn. Run your boat/outboard and see if it made a difference. If not, or not enough, repeat with the middle carb and if this still doesn't help, the bottom carb is next. Repeat the cycle until your outboard revs smoothly through the lower to upper rpms(1500-5500). If you are past two full turns out on each carb and it isn't helping, your problem likely lies elsewhere. This worked amazingly for me and my 1984 I6 115hp has run like a dream since. I wish you the same good fortune.

 

[Bill73x]

Re: 1985 Merc 115? falls on its butt

Thank you squire. I'm gonna try squirting some fuel in while running like Jimbo suggests first. That way I will know which carb to concentrate on. My Father-in-Law swears that it is a sticking high-speed needle in the bottom carb. If thats the case I'm gonna try to find someone to re-build all 3.

 

[Chris1956]

Re: 1985 Merc 115? falls on its butt

Bill, That motor does not have even one "High speed needle". The carbs are real simple. They have a idle jet with a mixture adjustment needle, an inlet neede and seat, a main nozzle and a high speed jet. Make sure the float height and drop are set properly, the carb's passages are clean and the idle mixture is set a bit rich. If the carb mixture is set for max RPM at idle, it will never rev up. It must be 1/8 turn richer than the setting for max idle speed, or more.

 

[CharlieB]

Re: 1985 Merc 115? falls on its butt

You mentioned that your motor uses surface gap spark plugs but you didn't say if you have changed them.

Partially fouled plugs will idle and take a small amount of throttle until the load gets to great for the plug to fire, then it shorts and the engine bogs, sputters, or falls on its face.

Recheck your plugs, sometimes the simple things elude us.

 

[jimmbo]

Re: 1985 Merc 115? falls on its butt

Here is a dirty way that might clean the carbs without disassembling them. I have done this and it has worked but, no guarantties as it is not the best way. Mix up a six gallon tank of fuel using a 32:1 gas oil mix add a couple of cans of combustion chamber cleaner, Power tune, or Sea Foam. Shake tank to mix well. Start engine using regular mix. Once engine has warmed up switch to the witches brew. Run engine at fast idle for a bit then shut down, spary some(not a lot)more cleaner into the carb throat, wait a few minutes and restart. With engine in gear run at various speeds including where the stumble, surging occurs. If the problem is gum or varnish this might dissolve it. Use a clean tank too, a gummed and varnished tank would create other issuses

My 84 115 hated pulling skiers. It would be running great, plenty of grunt, hook the ski rope to the pylon... BOG. Unhook the rope, ran like a charm