1994 120 force o/b won't start

[brian66r1]

Re: 1994 120 force o/b won't start

Thanks again Frank.

I made up this little test board jigger to ground the plugs whilst I'm cranking the engine with the plugs out. It does well. It's just a bit of nice marine ply with 4 X 15mm holes in it and piece of wiper blade metal under each washer. Then I just attach a short little jumper lead to the motor and watch the spark. These plugs are the ones I pulled out, the BUHW ones and for some reason the spark is nowhere near as strong with these as with the correct BUZHW ones in. The only difference between them is that the BUZHW ones have about 55 Ohms resistance between the top of the plug and the centre electrode. My carbs have that air bleed jet underneath that plastic screw in cap in photo 3 and it came out clean as a whistle, blew carb cleaner through that fine. On the inside of the carbs on my engine where you show the 1 hole at the top of the butterfly, I have 3. One is the same size and in the same location as in yours but I have 2 much smaller holes there just to the starboard side and a little further back towards the engine. Anyway, the carb cleaner sprayed nicely out of all these holes too.

The brass dip tube allowed a nice stream of cleaner to spray through it also.

I'm going to remove the bowls off the carbs, remove the plugs, spray a bit of oil rich pre-mix in through the plug holes for lubrication, crank it for 30 or 40 seconds with throttle wide open (and no fuel going in) then put everything back together put 5cc of fuel in each cylinder put the plugs back in and then it's going to start and run like a dream. No! Hang on a minute. This must have been a dream I was having.

Brian

 

[carholme]

Re: 1994 120 force o/b won't start

Brian;

I don't know if this has anything to do with your problem but I think I see an Advent Calendar in a few of your photos and I sure hope that all of the flaps are not opened as we still have a few days to go yet.

Gerry

 

[brian66r1]

Re: 1994 120 force o/b won't start

I am amazed. I just had a look and it is actually up to date. The treat for the 20th is still there and the special one for Christmas eve has been peeled open in the corner a bit but it is still in there.

It has restored my faith a little

Brian.

 

[brian66r1]

Re: 1994 120 force o/b won't start

Now.

I tried the above. I also used the air compressor and blew through the carbs with the butterflies wide open and the bowls removed and the flywheel at various angles just to ventilate the cylinders and crank cases a little more (couldn't hurt), and I could hear the reed valves vibrating at different angles so there's no problem there. Before I put the teaspoon of fuel in, I tried cranking for 15 or 20 seconds to see if it might come good by itself and no! When I took the plugs out I wiped them on a roll of paper towel and plug 1,2and 4 were dry as a bone. Plug 3 was wet enough for the paper towel to absorb the fuel off it and leave a bit of an imprint behind. I put about 5cc's of fuel in each plug hole and tried again. Still no!

Just to eliminate the possibility that the fuel pump was crook (even though the diaphragm is good and in tact). I cracked the fuel line off the top carb and placed it into a glass jar and cranked the engine. It pumps fuel out like it should (pulsing spurts).

Frank, if I brought you out here to get the thing going for me, I think it would have you stumped. I've been around bikes for near 40 years and I've had bikes (2 and 4 stroke) that have at times been a bit tricky to get started but I have never had a bike that I could never get going. Not like this. This is just horrible.

I'm thinking now to pull off the carbs again and rig then up to a gravity fed fuel supply and use my air compressor to blow air through them and see if I am actually getting fuel coming out of the holes at the top of the butterflies.

Frank, inside where the air bleed jet is, there's just the screw on plastic cover, then there's the jet itself and that's it isn't it? When I remove these jets and blow through the passage, with the mixture screw removed, I should get carby cleaner come out through all holes above the butterflies and also out the hole where the mixture screw is. That's correct isn't it? And the mixture screws are turned out about 1 and 1/8 to 1 and 1/4 of a turn from home?

Please anybody, feel free to come up with any more suggestions. I'm getting tired of seeing the thing sitting there every time I walk out the front door. My missus is is getting a bit fed up with it too.

Brian.

 

[pnwboat]

Re: 1994 120 force o/b won't start

It would appear that you've gone through the carbs pretty good.

Have you performed a compression check yet?

Also you might want to pull the reed assemblies out and take a close look at them. It's can be hard to see any problems with the reeds by looking at them with just the carbs removed, unless there is a reed petal that is completely gone.

1994 120HP motors had several types of ignition systems. Does yours have a "switch box" with the black coils?

 

[brian66r1]

Re: 1994 120 force o/b won't start

Thanks for the reply pnw.

I did a compression check a month ago when I first started having this problem and they were 120-140-120-120 or something like that. I meant to do one earlier today but didn't get around to it. I will make the effort tomorrow.

I had first thought of the reed valves as a possibility when the problems first started but today whilst I was pumping air in through the carbs. At certain angles on the crank you could hear the valves humming or vibrating just like they should. That would come pretty close to discounting them as being the fault. I also recall having a really good look at them from the outside when the carbs were off and I'm almost certain there was no visible damage to them (petal missing etc).

As far as the ignition goes. Yes i think it is the one you are referring to with the switch box and the black coils. It looks like the one in this diagram.

http://www.seawaymarine.com/pages/o..._(91D,92C)/06-002-823644-4790/FORCE8236444011

I'm more than happy with the quality of the spark now though. With the wrong plugs in, it was very weak but now it is fantastic.

I keep thinking it is a timing issue but if the timing was out by any amount even 90 or 180 degrees I would surely still get a backfire out the exhaust or even through the carbs wouldn't I?

Might be worth mentioning too. When I had someone cranking it for me the other day and I had my hand over the opening on the top carb. I could feel the suction and my hand was getting wet from the fuel but it wasn't a constant sucking, it was pulsating and it felt like it was puffing out through the carb more than it should?

I should take some video and post a link so you can see and hear it. It might give someone another idea.

Brian.

 

[Nordin]

Re: 1994 120 force o/b won't start

Now you have to check the timing. You have fuel, you have spark, you have compression. Is it spaking in the right time? Probably not.
Check with a strobelight aming at the timingmark at flywheel. Should be about 0-2dgr. at #1 plug when throttle in idle possision.

 

[stubtail]

Re: 1994 120 force o/b won't start

You can get a good idea of how close your timing is without a light. Use a screwdriver or something long enough to insert into the #1 (top) cylinder through the spark plug hole (ensure whatever you insert is clean!), rotoate the flywheel in a clockwise direction, and get a "feel" for where top dead center on the #1 piston is, by the maximum projection of the screwdriver from the cylinder head. There should be a mark embossed on the outer rim of the flywheel (just inboard of the teeth) that will or should be very close to the 0 mark on the pointer plate.
If Frank has his ears on, I'm sure that he would be able to provide you with a more accurate procedure with details from memory! I guess the point I am trying to make is that at this juncture, a timing light is not essential.

Cheers.

 

[Frank Acampora]

Re: 1994 120 force o/b won't start


here are a couple of photos of reed assemblies. These are white but essentially the same as yours. You can also see the gaskets I am making and the black plastic vee block mounting plate.
Your engine should have rubber covered reed blocks and square tipped reed petals. Reed assemblies are one way valves to let the piston pressurise the crankcase and deliver air/fuel to the cylinder. A broken reed petal will stop this. It is possible that a reed petal or two may have broken, but certainly not in the realm of probability that all cylinders have broken reeds and the engine should start and run on even as little as two cylinders.

However, if you are getting fuel to the carbs and no fuel to the cylinders, then reed assemblies would become suspect.
Remove the carbs and look into the manifolds--inspect the vee blocks and reeds. Worst case: Remove the manifolds and inspect the vee blocks---in fact, do it anyway! I just remembered back a time when the screws holding my vee blocks came loose on two cylinders. Power was way down. Loose vee blocks will not seal against the gaskets and will not allow pressurizing of the crankcase. Also check the vee block mounting plates: They are plastic on later Force engines and may have broken. Be careful and work slowly and you may be able to re-use the gaskets. If not, buy some 1/32 inch gasket paper from the auto supply and make your own. They are relatively easy to make. 1/16 inch gasket paper is too thick and 1 mm may be too. 3/4 mm if they offer it might be about right. If the vee block screws are loose reseat them with threadlock compound.

Do not neglect to check that the flywheel has broken the key and is now off timing. The center magnet inside the flywheel controls the pulses to the trigger. If it is in the wrong place, even if the trigger ring is correctly set, the plugs will fire at the wrong time. Set the piston to TDC and see if the flywheel zero mark lines up with the pointer on the block.

Back to your question on the carbs: The small brass tube comes up into the top of the carb casting. A hole is drilled in the side of the casting and capped with a brass plug. This hole connects the brass tube with the jet and the needle passage.. Now, the carb I showed you has one large hole behind the butterfly and three smaller ones in front which can not be seen in that photo. At idle, fuel is delivered through the one large hole and the three small ones act as air bleeds. Since at low RPM, not enough air is passing the venturi for it to deliver fuel, as you crack the throttle open, the three small holes progressively are exposed to manifold vacuum and start to deliver the extra fuel the engine needs. Your carb may have a different number of metered holes, but the principle is the same. The main venturi dip tube does not deliver any fuel until the throttle is about 1/4 open but when it does--- Once you get the engine running again leave the black covers off and have someone give the engine full throttle while you look in. You will be amazed at how much fuel is vaporized.

 

[stubtail]

Re: 1994 120 force o/b won't start

Looking back at your 4th picture from a couple days back, the photo has been taken looking into the venturi of a carb. It appears as though the dip tube does not extend into the casting at the top of the venturi, or is that a shadow I'm seeing? I looked at a few spare carbs I have sitting on my tool box here, and the dip tubes bury themselves into the top of the venturi, covered on the top of the carb by a small brass plug.

 

[Frank Acampora]

Re: 1994 120 force o/b won't start

I'll be damned! Good eyes PNW. Sure does look like the low speed dip tube is not up in the casting where it belongs. But: What you are seeing is the air vent just in front of the dip tube. Compare it to my carb photos.

 

[brian66r1]

Re: 1994 120 force o/b won't start

Don't believe what you're seeing. It's just trickery. Done with lights and mirrors. The thin tube is definately inserted hard into the top of the carb housing. Just removed all the plugs (earthed the leads of course) and did another compression test. Throttle pegged wide open, 1-130, 2-145, 3-140 and 4-140. If a reed valve was malfunctioning then the air fuel going into the crank case would not be transferring through the port into the cylinder when the piston was coming back down. It would be blowing back out the carbs and I wouldn't be getting such good compression?

I checked the timing mark on the flywheel against TDC on number 1 piston and it visually lines up. The wiring loom that comes from the signal generator under the flywheel has a bit of movement when you gently tug on it and it causes the timing advance lever coming off the throttle lever to move a little also. I haven't had the flywheel off as yet but I imagine that for the timing to advance when the throttle opens, the signal (pulse) generator must have to move?

Also. If I used a timing light (which I havent got) and checked without the engine running just while creaking it over. That will be accurate won't it?

Brian

 

[Frank Acampora]

Re: 1994 120 force o/b won't start

Don't remove the flywheel. Since the timing marks line up with the pointer, it has not broken the key. The aluminum part under the flywheel that advances timing is the trigger. There are four coils in it corresponding to the cylinders and their firing order 1324.As the center magnet in the flywheel passes each of the coils it induces a low voltage pulse which signals the Cd box to dump its capacitor into the spark coil. Timing is advanced by moving the trigger into the direction of flywheel rotation so the flywheel magnet passes the trigger coil earlier.

These engines use a self energising ignition system which must turn at a minimum of 350-500 RPM. any lower than that and they can not generate the voltage necessary to charge the CD boxes. Thus: you can not check timing by spinning the flywheel by hand.

At any rate, I doubt it is a timing issue.

Throttle position and crankcase pressure will have no effect on compression ratio test results. Since both bypass and exhaust ports are open at the bottom of the stroke, the cylinders go to atmospheric pressure no matter the position of the throttle or how much or little pressure is in the crankcase.

Check for air leaks in the crankcases. Check the reed vee blocks and check the bypass port covers. Be certain that the covers are all tight and the gaskets have not broken.

 

[brian66r1]

Re: 1994 120 force o/b won't start

The reed valves are OK. The block for cylinders 1 and 2 are pictured below:

And from the other direction:

And from the under side:

And the reed block from cylinders 3 and 4:

And from the other side:

And from the under side:

The reed valves were sticking a little bit to the vee blocks because they were wet with a little bit of fuel / oil. I lightly pressed each petal away from the vee block from the under side with my finger and they all made a clicking sound when they separated from the block. I held the block up to the daylight and I couldn't see any light coming through. They are fine.

All the port covers are in tact, tight and it doesn't look like any gaskets have blown out

??????????????

Brian

 

[brian66r1]

Re: 1994 120 force o/b won't start

I just got a little bit exited then. I saw that the transfer port covers were pretty wet from the top down and I found that this vacuum fitting was very lose. It could not have been making a seal:

I tightened it and re routed the vacuum hose. Put the switch block back on, put the engine cowl back on and cranked it and guess what? It didn't do anything. It just turns over and over and over again.

This is my throttle control Frank. You mentioned earlier about pushing a button or pulling a lever to raise the revs without engaging the gears. All I do is lift the fast idle lever and it opens the butterflies about 1/10.

Not that this matters too much right now. I can have it open, closed, up, down, any way I like and it doesn't make any difference. It just turns over and over and over. Without even a hint that it is going to fire.

Brian

 

[pnwboat]

Re: 1994 120 force o/b won't start

Maybe check the ignition system??? I've been fooled a time or two by visually checking the spark at the plugs. I've learned that just because you have spark, doesn't mean that the ignition system is working 100%. I made a similar rig as you have several years ago to test spark.



I've looked at the spark on the Force 120HP motors with the 1996-1999 Mercury Thunderbolt CDM ignition systems with the BUHW NGK plugs with this set up. The amount of spark does not impress me. The spark is not very bright but it is blue in color and you can hear the "snap". I assume this is normal because the motors that I've tested run great.

It seems like you've pretty much eliminated the reed valves, carburetors bypass covers and fittings etc. Pretty much everything that has to do with air and fuel delivery. Maybe check out the stator. If you have Blue and Yellow stator leads, you should see between 680 - 850 ohms between them. If you have a Green/White and White/Green stator leads, you should see between 500 - 700 ohms between them. Also the Black stators seem to be more prone to failure than the Red ones. You can look up underneath the flywheel and see the stator.

 

[brian66r1]

Re: 1994 120 force o/b won't start

I thought it funny that when the BUHW plugs are connected to the leads and I crank the engine the spark is blue but very weak. Now that I've got the correct BUZHW plugs in, the spark is greatly improved. By the way, your test rig ****s all over mine too.

I'll check those readings on the coils later today and I'll try and take a quick video of the plugs sparking compare the 2 types of plugs. I cant believe how many times I have removed the plugs from this motor in the last 4 weeks

Brian.

 

[pnwboat]

Re: 1994 120 force o/b won't start

I know what you mean about removing the plugs. I've had a few instances on problem motors where I thought that I'm going to either strip out or wear out the spark plug threads before I get the problem fixed! LOL! Anyways stick with it and I'm sure with the help available on this Forum you'll eventually get it going.

 

[brian66r1]

Re: 1994 120 force o/b won't start

Tried and tried and tried it again. Tired of trying.

Is it possible that the head gasket could be blown in some way and some how not showing any extreme irregularity on the compression test?

It really concerns me that when I remove the plugs after cranking the motor over that only the number 3 plug is wet when I remove the 4 plugs.

Also, I'm pretty sure this is correct but the other interest in my boat thinks it unusual that exhaust comes out through the pee holes. This is correct isn't it? The exhaust is supposed to come out of the 2 pee holes on the rear of the lower cowling?

Brian.

 

[Frank Acampora]

Re: 1994 120 force o/b won't start

Those are not pee holes. They are idle relief vents and yes, exhaust will come out of them on muffs or when the engine is sitting low in the water.