1986 Merc 115HP Stalls With Load

[akendall]

Specs:
1986 Merc 115HP (Standard Prop) on a 1979 17ft J-Craft.

Symptom:
-Motor runs great free of load (no waterskier/tow) from slow to full throttle (~5300RPM) even when hammering it, idles great as well. However, when trying to pull a waterskier out of the water it stalls.
-Dragging skier between 900-1500RPM before "hitting" the throttle makes this stalling condition NOT happen.

What's Been Done So Far:
-Compression test - passed
-Got spark on all spark plugs and when pulling them as the motor runs there is a drop in power... so I guess that means they're workin'
-Stator low and high windings passed

-Now I've been told to look deeper into the carbs, one method is to actually to cover each carb up with a rag for a short duration, one at a time while running - and if I see gas flows onto the rag that means that the carb is getting gas - if not then the carb isn't and it needs to be overhauled - does this sound like a good test to you guys?

Anymore suggestions will be appreciated! [img]/infopop/emoticons/icon_smile.gif[/img]

[gw204]

Do not cover those carbs with a rag. If the gas goes into the rag, it's not going into the cylinder. Since the gas contains the oil, the cylinder won't get the oil and a possible kaboom could be on the way. How old are you spark plugs? That's the first thing I would change. It's much easier to change plugs than to rebuild the carbs. Have the carbs ever been overhauled before? Do you winterize properly with fuel stabilizer and then run the engine to allow the stabilized fuel to get into the carbs. It's very possible that the carbs do need an overhaul but start with the easy/cheap stuff. Maybe you'll get lucky.

In any event, carbs are easy to rebuild. Each rebuild kit (gasket kit) costs about $7.00 and you'll need one for each carb. Depending on the condition, needles, seats and floats may be in order as well but they're not terribly expensive either. I rebuilt (new gaskets, cleaned parts, new needles and seats) the three carbs on my 150 Merc myself for less than a third of the cost to have it done.

Brian

[bucket]

Thought i had carb problem om 150 Merc, Glad i put new set of NGK plugs in first cause that was the fix . Go the easy route first.

[akendall]

Thanks "gw204" and "bucket" for your responses - much appreciated!

I'm going to the boat this weekend and will try the new plugs, and then if my problem continues I will proceed with the carb rebuild...

"gw204" - I winterize the engine every fall with Quicksilver Engine Storage Spray and completly run the fuel out of it as well as fogging the carbs and cylinders (with the plugs out after). Do you have any suggestions on how I may be performing this task wrong?
As well, was it difficult to resync the carbs with the throttle once re-installing them after the cleaning?

Anyone know what the (up-to-date) plugs are for this engine? I have a Seloc manual, but it's pretty old itself...

Thanks! And I appreciate the reponses! [img]/infopop/emoticons/icon_wink.gif[/img]

[gw204]

akendall,

Regardless if your boat has a permanent or portable fuel tank you should (and this is only my process, others many have varying opinions) be filling the tank with fuel and adding the appropriate amount of fuel stabilizer (I use Sta-bil) to the gas. After you do that and are sure the two have mixed well (I leave it sit a few days), change your water separator and run the engine on the garden hose off the main tank long enough to allow it to flush out thoroughly and let the stabilized fuel permeate the entire fuel system (lines, filters, carbs, etc.). Once you are sure the motor is getting this stabilized fuel, then add the fogging oil or storage spray. I don't run the engine out of fuel as the fogging oil instructions say to spray the stuff into the carbs while running so it can get sucked deep into the engine. I spray it longer enough to almost make the engine stall and then shut it off. Don't let it run long enough to burn off all the fogging oil. Pull the plugs, spray in cylinders and reinstall the plugs. Stabilizing the fuel is the critical thing here. Without doing this, gas breaks down and become more like a varnish and WILL clog up carbs. A full tank helps to prevent condensation build-up which results in water in the fuel.

Change the lower unit oil, grease all fittings including the prop shaft, leave the engine tilted down, remove the battery/batteries and button her up for the winter. Now is a good time to have the prop reconditioned if it needs it.

Smokes a lot in the spring when you first fire her up, doesn't she!?!?! That's normal. If winterized properly, it should start immediately. Hope this helps.

If you go to NGK's website, it will help you verify the spark plug number:

http://www.ngksparkplugs.com/apps/wa...ft/default.asp

I would then check that number with you local Mercury dealer to verify it is correct. If you don't like NGKs, most auto parts stores can cross them to the brand of your choice. Most people are going to recommend NGKs.

Good luck. Let us know how everything turns out.

BTW, I didn't perform the carb. synch. So far that's the only thing I left to a "professional".

Brian

[akendall]

Once again - thanks so much for the great advice 'gw204'!!! I'm going to need that winterizing info in a few weeks!

As for the plugs - I'll let you know how it goes, and if it indeed corrects the issue... if not I'll be overhauling the carbs next spring.

Thanks again,
~Andrew

[KABOB]

Andrew,
Brian knows his stuff. To reiterate one thing: running the engine completely out of gas (until it stalls) is not a good idea with a 2 cycle engine - starved for gas = starved for oil. (Unless it's oil injected, then not sure what happens.) But you'll NEVER get all of the gas out of the carbs and other points in the system anyway, and it will varnish up on you. Follow Brian's recommendation of stabilizing the fuel per the label directions, then turn off the ignition right after fogging the engine until the point where it's choking on the stuff. Pull plugs, spray more in cylinders, rotate flywheel manually as needed to distribute the oil.

[gw204]

Good call Kabob. I forgot about turning the engine over a few times after reinstalling the plugs.

Oil injection on this Merc 115, as well as my '85 150 works by mixing the gas and oil via a gear driven pump prior to the fuel pump. So you are correct, starving the engine of fuel also starves it of oil.

Brian

[akendall]

Thanks a million for the advice guys 'gw204' & 'KABOB'!

I'm pretty sure that because of winterizing my engine for the last 5 years without stabilizer in the fuel + no carb cleaning, I'm running into some kind of problem with the carbs/floats sticking due to a varnishing condition.

This fall I'll winterize the engine as you guys have explained and then overhaul the carbs in the spring - that probably makes the most sense because I'll have fuel sitting in the engine (although this time it will have stabilizer in it) for another 6 months until next spring - you guys agree?

Thanks again!
~Andrew

[gw204]

Yep, five years with no fuel stabilizer tends to cause problems. How long is your boat winterized each year?

Anyway, still do the fresh plugs before winterizing and doing anything to the carbs. That will give you two basilines to compare to after you run it with fresh carbs. Run the new plugs to get an idea if they helped any and then put the old ones back in when you winterize. Save the new ones for next year. I like to put new plugs in every spring.

If you're going to be doing it yourself, start your carb. rebuild about a month before you would normally dewinterize. A full time mechanic quoted me three hours for the entire job. It took me significantly longer than that but I guarantee I did a better and more thorough job. It's not that expensive so consider replacing all of the needles and seats. While you are in there, also replace all the fuel lines and rebuild the fuel pump. If your pump is like mine, it is a diaphram pump that is driven off of crankcase pressure. The diaphram wears out over time becoming brittle and developing small pinholes. The fuel pump rebuild kit should be less than $10 American. It includes a new diaphram, new gaskets, new check valves and a new fuel screen. That took me about 30 minutes to complete. If you don't already have it, add a small in-line fuel filter prior to the oil pump. Should only cost a few $. I can't begin to tell you what wonders all this did for my engine.

Doing all this early will ensure you won't lose any on-water time when the season gets under way and the fish start biting.

Good luck. Email me if you have any questions. gw204@hotmail.com

Brian

[Harpoon]

Check for water in your fuel or fuel separator.

I had the same syptoms once.

PP