At what engine speed should the trigger voltage be tested at on a 1986 mercury classi

[halmc]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

It was scary to replace it because the price for the SB was a bit more than a non-running motor was worth. Sort of a double or nothing enterprise. Good luck, irrespective of which direction you take.

 

[CharlieB]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

................ Outboard ignition says to swap the wires around such as 1 for 3 and 2 for 4 and see if the problem changes to the other cylinders but when I do that the engine will not even turn over.. As always any help will be greatly appreciated..

Swapping trigger wires on the switchbox tests the switchbox, you will also need to swap the output wires to the coils so that trigger ! is still firing coil 1, etc. This test will only tell you if the switchbox is having a problem with a specific cyl.

When Ohm testing triggers are all trigger wires dis-connected from the switchbox?

Are you using the Ignition Troubleshooting Guide that is available for FREE from CDIElectronics support pages? Theirs is the BEST source of troubleshooting and very highly recommended.

Have you tested spark using an adjustable gap soark tester set to 7/16 inch to see that the system arcs a hot blue spark?

Will the engine reach max RPM planing the boat?

Is this 'miss' only during acceleration then clears once the motor is near top RPM?

If so you may have a restricted idle passage in a carb causing a 'lean miss' during acceleration only, idling fine and once to RPM running fine on the main jet.

Depending on your answers it may be possible that you have a fuel problem and are chasing your tail thinking you still have an ignition problem.

 

[Coltrickle]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

When I ohmed the wires today I disconnected all the trigger wires and it ohmed out to spec all were open to ground and 850 across the bottom and top two wires.. I did moved all of the coils around and still the bottom plug is clean.. The top 3 plugs have a black looking oil/gas mixture on them and the bottom plug looks to have a lighter looking fuel mixture on it. I cleans all of the plugs today and ran the motor at about 2300 rpms for 15 minutes.. I could touch the two bottom plugs with my fingers and they were barely warm while the top two plugs I could only touch for a few seconds.. I am still only getting 2.5 a d 2.7 volts out of my trigger at idle.. The engine misses through all the rpm range and I could never get the boat to plane.. Hope this info could be of some use.. Thanks again

 

[CharlieB]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

Model and serial # so I can check which carbs you have.

Your ignition is firing fine. I suspect you have either a idle mixture problem affecting low and mid-range RPM or a water leak between the #4 cyl liner and the engine block.

Look at the piston dome of #4 compared to the upper cyls, is it still 'steam cleaned' ?

Do the bottom carbs have idle mixture adjustment or is this the early 2 + 2 motor?

 

[halmc]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

Another insteresting aspect of my engine -- the one that a switch box corrected: desipte its tremendous misses, and of a somewhat random nature, I shorted each of the plug wires to ground in turn, and in each case the engine developed quite a bit less power. At idle, the rpm decreased, and under load, it made less power.

Your ignition might be firing fine, or it might not. To observe spark in a cranking engine or idling engine and to conclude from that observation that it has good spark is to completely ignore the increased difficulty that the spark encounters as cylinder pressure is increased with the engine running and under varying loads. That's so because the dialectric strengh of air is increased as it is pressurized. The greater the throttle angle, the greater the pressure, the higher the dialectric strength is, and thus the more resistance to a spark.

Lastly, an incorrect idle adjustment won't under any circumstances produce a miss at any rpm more than an idle.

 

[CharlieB]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

A 7/16 inch hot blue arc in free air is sufficient to cause the ignition to produce maximum voltage also found at high RPM under load at or near zero intake vacuum.

The idle circuit continues to flow fuel well into the mid-range until the air flow is sufficient to fully draw all full thru the main jet.

Some carbs have the idle circuit jet run parallel to the main circuit, those draw fuel thru both circuits at high RPM, some other carbs the idle jet draws thru the main well and only the main jet controls flow at high RPM.

Either case, two stoke idles must be adjusted richer than 'Best Idle' to provide the additional fuel for acceleration, they do NOT generally have accelerator pumps.

Even one carb still adjusted to 'Best Idle' can cause a 'Lean Miss' during acceleration, yet smooth out and run fine at top RPM and idle.

 

[Coltrickle]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

It's a 1986 classic fifth with the tyllison??? Carbs .. I have taken both of the apart and called myself cleaning and rebuilding them... But did not replace the jets.. Just cleaned thoroughly and replaced float needles and rebuild the fuel pumps on the side.. Oh the serial number is 0A916270.. Piston looks a lot better now.. Compression is 115 on top 3 and 110 on the number 4 cylinder..
Not sure about the 2+2 motor but the only adjustment I only see the on these carbs is a screw in the top right corner.. It also has a air jet on the outside face of the carb and main jet on the inside and that is all I seen..
The engine misses through all rpms getting worse the higher I go.. I also had the foot off the other day and started the engine revved it and shut it down.. About 3 seconds total and it still skipped.. So I know there is not any water getting in there with the foot off...
I appreciate all the info and knowledge.. Hopefully soon I will be have her going.. The crappie are ramping up again and I'm. Without a boat.. It a bad time for me!!! Thanks again!!

 

[CharlieB]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

Each carb feeds two cyls.

Idle mixture MUST BE adjusted while ON THE WATER and with the motor IN FORWARD GEAR, this is necessary to provide the correct exhaust back-pressure and operating load on the motor.

Starting point is the idle mixture screws 1 and 1/2 turns out from very lightly seated. This should give enough fuel to start, warm up and get into gear. From there adjust each screw very slowly until you get the motor to run at the 'Best Idle Speed'. Make very small changes, about a screwdriver blade width at a time and give the motor 30 seconds to a minute to burn off any excess fuel.

Once at 'Best Idle Speed' the idle mixture must be richened even more to provide the additional fuel necessary for crisp acceleration.

Turn out each idle mixture screws about 2 bladewidths then test acceleration holeshot, ANY bog, hesitation, lean cough, is proof the motor needs even more idle fuel. Back out each idle screw another bladewidth and repeat acceleration test.

Repeat to perfection.

 

[Coltrickle]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

Thanks Charlieb but just to be certain is the idle mixture screw used to set the idle and rich/leaness.. I only see one adjustment screw is why I am asking?? Sorry for all the questions but at this point I do not want to induce any more problems!! If I am correct when you back the screw out it gets richer and when you screw it in it gets leaner??? So if it does have the lean skip powering up I should back out on the idle mixture screw?? Thanks again!! She'll be at the lake Saturday..

 

[CharlieB]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

Idle mixture screw only adjusts idle fuel, out = rich

Idle RPM is adjusted with the idle adjustment screw on the timing lever, advance raises speed.

Hopefully you just need a screwdriver blade with or two turn out on an idle mixture.

 

[Coltrickle]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

Thank you sir!! I will let you know how she does..

 

[Coltrickle]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

Ok fellas I took her out today and she ran great... I adjusted the carbs while it was still on the trailer and backed down the ramp.. Then I took it down river and opened up the mixture screw about an1/8 turn each... She runs great... I am still however getting air into my fuel line and causing it to lose prime after a while... I have replaced all the fuel lines and connections except for where the line connects to the motor.. But I am not leaking fuel anywhere... This has got me puzzled but the main issues are all good.. Thanks everyone!!! Would have never fixed it without y'all's help!!!

 

[CharlieB]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

The O-ring in the disconnect fitting to the motor can fail when the pump sucks, and holds fine when pressurized by the primer bbulb.

Many remove the fittings altogether and run the fuel hose directly in to the fuel pump.

 

[oldman570]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

Your probbly sucking air at the connection to the motor as Charlie stated. I always use a small clamp that fits the fuel line and clamp the fuel bulb in an vertical position to the transom with enough extra slack to allow the motor full movement. It takes most of the strain off of the connection and keeps the ball in the primer bulb so it will seat as it should and not allow for back sifenfing of the fuel to the tank. The fitting on the motor can be repaired with a new O ring from most auto parts stores, but the hose end can sometimes be done also, otherwise new artermarket conectors can be bought. JMO
Oldman570

 

[Coltrickle]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

Ok gentlemen I removed the connection fuel connector at the motor all together.. I prime the line and start her up.. Within 10 seconds the filter is empty.. ??? I also meant to say that this motor went through 6 gallons of gas in about 45 minutes of riding.. Is this normal?? Also I took the boat back to the river with my son and nephew and she did not run as well with the extra 250 lbs.. It sounded great on the hole shot then bogged down and took a while to plane out.. 10-15 seconds or so... Then it would not accelerate past about 3/4 throttle.. Again she is doing a lot better but far from great!! Any more ideas???

 

[CharlieB]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

What filter is going empty?

You may still be sucking air into the system, a crack in the fuel tank dip tube, poor hose seal to a fitting, something.

Have you tried using a temporary clear hose to replace a fuel hose between the fuel pump and carbs? This will clearly show any air bubbles sucking in and reduce fuel flow necessary for WOT.

Just remember that once finished with repairs to remove that clear hose as it is NOT rated nor approved for fuel use, only for short term testing.

 

[Coltrickle]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

I have an inline filter just before the split in the fuel line going to each carb.. My fuel pumps are vaccuum style built on the side of the carb so there is not a way to see if they are introducing air into the system.. I am baffled by this.. I have nothing but straight line up to that filter except for my tank connection and primer bulb... I even removed the tank fitting and put the line directly into the gas with no luck!!!

 

[CharlieB]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

Test by leaving the filter out, it may be too restrictive.

If the motor performs better without that in-line filter then instead install a spin-on water separating filter which will flow far more fuel.

 

[oldman570]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

I also recommed doing as Charlie states. The fuel realy needs to be filtered before it gets to the motors fuel pump and not just the carbs. As for the fuel used, and planeing of the boat, with the added weight in the boat. The motor gets the best fuel usage and performance when the motor runs at or near the limit of its RPM range. A tach will tell if it is in that range, with the boat fully loaded to the manufactures load capacity. If it will not reach the recommed RPM, then a prop pitch change should be considered, as the motor is laboring and will use more fuel as a result. It will usally increase the RPM @WOT by 500 for each 1 degree of pitch loss and only lower the top speed about 2 to 3 MPH on most boats. Work on the fuel filter first and test the setup as it will make a diffrance before moving on to the boat motor prop setup, as it might be fine as it sets now. Make sure that all the fuel line and fittings are the same size from the tank to the motor.
Best of Boating,
Oldman570

 

[Coltrickle]

Re: At what engine speed should the trigger voltage be tested at on a 1986 mercury cl

Could you gentlemen tell me the correct float height for the carbs.. Thanks