1985 Force 85hp Idle issues

[johnnj150]

Hey guys. I have a question regarding my 1985 Force 85hp. It is the 3-carb, distributerless ignition model w/3 coil packs. I purchased this boat (1992 capri) as a project and I havent had it on the water yet.

My issue is: I can start the engine and it runs (by my ear I am thinking about 400-500rpm) (so pretty low) when the Idle is advanced by placing the shifter in neutral and fully advancing it. After 2 mins of warming up I begin to back off the throttle to center neutral position and as I move it back the rpms drop and the engine dies about 1/2 way travel between full advance and center neutral.

I am an auto mechanic by trade, so I figured this would be no problem but I fully admit when I know nothing about what I am dealing with and I've never worked on outboards before. I have a shop manual for the engine.

This is what I know:

The compression is good.

There are three brand new plugs of the correct type (ngk buhx installed).

Fresh pre-mix 50:1 fuel is in the tank.

All carbs are completely clean, no needles are stuck. Idle mix screws (located on the front of the carbs and behind the rubber grommets in the intake manifold) are set at 7/8 turns out from a light seat as per the initial adjustment specs.

I have correctly adjusted the choke plates and solenoid as well as the throttle plate linkages.

The mark on the throttle cam is lined up exactly with the center of the plastic roller attached to the carb linkage when the throttle is in center neutral.

There is no contaminants in the tank, the fuel screen is completely clean and no obstructions such as in-line fuel filters are installed. (once i get it running correctly I will install one).

The only thing I havent checked so far is ignition timing. It is very odd though because this doesnt seem to be behaving like a timing issue. Most of the hondas I work on will idle in neutral even with timing fully retarded or advanced. I will check the timing when I grab my light from work. Can I just ground the plugs and leave the prop on the engine to check it? I assume the manual says remove the prop for safety reasons moreso than actual performance.

Any help would be appreciated, I really dont want to have to spend money to get this figured out.

 

[johnnj150]

Re: 1985 Force 85hp Idle issues

Ok guys, Ive refined this into some more specific questions:

Again my engine is a 1985 Force 85hp with distributerless ignition.

1. Can I go ahead and adjust the carb idle mix screw (located behind the gromets on the intake minifold) to proper setting while the engine is running in Fast idle mode (throttle lever in neutral + forward)?


2. My carbs have an idle mix screw (the one behind the gromet) and a brass screw on the same side as the choke rod, with a hole in the center. This screw isnt apparently attached to any kind of spring. Is this some sort of vent which is interchangable for different atmospheric pressures? I guess I am a little perplexed there is an idle mix screw but no low speed/highspeed adjustments.

3. On these force engines, are the throttle blades supposed to be FULLY closed when at idle w/shifter in center neutral position, or...like some cars, are they meant to idle with a mm or so of opening in the blades?

4. Wouldnt timing be the very last thing I adjusted, AFTER I was able to make the engine idle at center-neutral position?

I am convinced the reason my engine is dying is simply some settings I have off, as Im a total virgin setting up one of these engines. I noticed the overall idle adjustment screw (not on the carbs) just moves the virtical bar slightly (moving the position of the throttle cam and the timing), so thus...if I need to raise my idle...it will definately put the mark on the throttle cam off from my original setting on the plastic roller attached to the throttle linkage. Ugh.

I really hate my manual.

Can any of you give me a plain jane procedure to set up this thing...once i get it idling I will be able to take it from there no problem. I'm an ASE master tech and right now I feel like a complete moron

 

[pnwboat]

Re: 1985 Force 85hp Idle issues

Sounds like you must have the SELOC manual. If so, you might try to get a CLYMER or factory manual on line.

Make sure that you do a Link and Sync on the carbs. All of the butterflys on the carbs need to move exactly the same.

1. Probably not the best way to do it. Increase the idle speed with the screw on the vertical shaft. Once you get it to idle, then adjust idle mixture on carbs. May have to go back and forth a time or two before you get it squared away.

2. There is no high/low speed mixture adjustment. Just idle mixture. Normal setting is 1 to 1 1/2 turns out from lightly seated. Better to run a tad on the rich side to prevent a lean condition resulting in a melted piston.

3. Not sure about this one. I looked at mine and they are slightly opened, but I wouldn't assume that this is the norm.

4. Timing can be done before or after. That is if you use the static timing method. Book calls for 32 degrees advance. Some folks limit it to 30 degrees to be safe to prevent possible detonation. These motors were made when leaded gas was the norm.

The plastic roller that the throttle cam rides on is adjustable. It's slightly off center, so if you loosen the nut that holds the pin in place and turn it with a screw driver, you can move it forwards or backwards. I wouldn't worry too much about getting the mark on the throttle cam to line up perfectly.

 

[johnnj150]

Re: 1985 Force 85hp Idle issues

thanks for your response.

I will take a look at it. I am really confused though, because the idle adjustment screw on the tower shaft just rotates the throttle cam. When you adjust your throttle rod and carb linkage the procedure is to line up the mark on the plastic roller with the mark on the cam. (I know this is adjustable w/the screw on the roller).

My point here is, as soon as you go about cranking the idle screw out to adjust your idle, that mark will no longer be aligned correctly when you are idling, which begs the question...what is the point of the mark. Likewise, if you rotate that plastic roller after the fact to correct this...you negate any adjustment you just made.

My idle mix screws are set correctly, and I will check again but I am damn sure my carb blades are opening correctly. I am sure I could adjust it so it idles with the blades slightly open and the mark not directly on the roller, it seems like if I need to do that something else is off.

Can anyone else confirm whether or not their motors idle correctly with that mark on the cam not perfectly aligned?

 

[pnwboat]

Re: 1985 Force 85hp Idle issues

Everything that you state is correct. My particular motor is probably not a good example as it has some minor internal modifications which has an affect on the settings.

One other thing that came to mind is the fuel recirculation circuit. On these Force motors, fuel has a tendency to puddle in the by-pass passage at idle and low speeds. There are some drain valves to pull this fuel out and recirculate it to re-burn it. If the valves are clogged, then you may experience poor idle quality, excessive smoke etc.

One other thing to check is the compression. Compression has an effect on idle and starting qualities. If you're seeing something in the neighborhood of 110 to 130 LBS, that's about average for a used motor. 150 LBS to 160 LBS is typical of a new motor. If compression is down, then there is a good chance the rings may be bound up in the piston groves from carbon. The rings on two stroke motors are not free and do not spin around in the groves like they do on four stroke motors, so it's very easy for them to get carboned up. You have to perform a de-carb to free them up.

 

[johnnj150]

Re: 1985 Force 85hp Idle issues

Ok, I just decided to take a stab and assume it was lack of fuel. I was right. I adjusted the cam (which a guy at a local boat shop told me today is a wearable part despite being up against a plastic roller) such that the throttle blades are slightly open at idle. Now the engine idles decent with the lower unit submerged in a plastic container. I still have about equal play in my main idle adjustment screw on the tower rod going either direction, so I will leave it where it is at.

I have a can of Johnson engine tuner spray, which I intend to run through the engine when I put the boat in the water, to help decarbonize it, as you mention.

I guess I just need to assume my throttle cam is a bit worn and say to hell with making that mark line up?

The throttle stop is set so the blades open exactly to full position when throttle lever is wide open, and at idle I guess they're open just enough for it to idle properly.

I guess I will see how it does out on the lake. Any other suggestions you guys can think of before I take her out? Theres only so much testing I can do in a plastic tub of water in my front yard.

 

[pnwboat]

Re: 1985 Force 85hp Idle issues

No I think you're all set to go. Normally I change the fuel pump diaphragm and the water pump impeller on a motor that is new to me just to be safe. Cheap insurance.

I bought a motor from a guy that told me he would start the motor up out of the water for a few minutes to warm it up before launching. Didn't know much about outboard motors and impellers at the time. Apparently neither did the guy that I bought the motor from. Started having cooling issues. Changed the impeller and made a world of difference in water flow out of the exhaust. Impellers need water to lubricate. Running dry is very hard on them.