1985 115 hp Mariner inline 6 idling and spark issues.

[ziggieman]

This engine has been just a pain in my you know what , It will jump on plane and run like a dream (Top Side) , but it idles too high and i cant get it to idle any lower. I was checking the spark the other day, and had no spark on Cylinders #3 and #5. I put the muffs on and let it run for a while, when I checked it again only got spark to #1 and #6, I decided to check it running and was getting spark to all 6 Cylinders.Is it normal to have spark to all cylinders when running, but not when just turning over the engine.

 

[ziggieman]

Just for the know , when I bought this engine it was very hard to start ,it would start and run on the muffs, but would kill when I tried to put it in gear on a load, so I pulled the carbs , and found that the float bowls were sticking, cleaned them really good ,and set the legs on spec per manual. After reinstalling them, setting the idle mixture screws to 1 3/4 turns, it fired up and ran like a champ. I then started to try and idle it down ,for I noticed It jerked into gear when shifting from neutral. Keep in mind , I am not an outboard technician , but I am very mechanically inclined and I also have the manual on this engine. It idles at around 1400 RPMs and the manual specs are between 650 - 800 . Compression check was good on all 6 @125 even, Set top end to 20, and I don't care how much I adjust on timing, I can't get it to idle down less than 1400 RPMs without killing as soon as I try to shift into gear . unless I have the spark advance adjustment screw backed almost all the way out .so im thinking it has to be something with the Trigger ,Stator ,or Switch boxes. Now I don't know how, nor have the equipment to test these things ,and I don't have a lot of money to buy parts that I don't need. With this boat running 53 mph WOT without a sputter on a 18 1/5 foot bass boat what could be causing this idling problem ? O, yea I Disconnected the Idle Stabilizer and it started to run really bad , so I re-connected it and it settled back out. I'm lost .... Can someone help?

 

[Chris1956]

That motor should have spark on all cylinders, all the time it is running. Idle pickup timing is 0-9* ATDC. Do you have that set properly?

To be clear, idle pickup timing is the spot when the carbs are just ready to open. Unscrew the idle stop screw and adjust the throttle cable to push the throttle closed, to lower idle speed. Retard the idle pickup timing to make it happen.

Some timing lights have the ability to enter the advance you want. Hopefully yours is not like that, as it can mess the timing up.

 

[ziggieman]

It does have spark on all cylinders when running , just when im bumping it over to test spark individually is when im only getting spark to certain ones .... weard isn't it ..

 

[Chris1956]

That motor need to turn 300RPM to have spark. Bumping it may not achieve that speed. That is likely what you are seeing.

 

[ziggieman]

OK , thanks Chris1956 , Im not sure how to set the Idle pickup timing . Is their any special tools required ? And can you lead me in the right direction ? Also when i shift in reverse and throttle up it seems to be jumping constantly instead of going into reverse like it should , Maybe its all a related issue. This didn't start until I started screwing around with the shift cables .

 

[ziggieman]

I will be off tomorrow so ill have plenty of time to work on it . Any help would be greatly appreciated .

 

[ziggieman]

__________________________________________
Manual specs are different for each but this is close enough to get them all REAL close. This assumes nothing is broken or "wrong" with it. This also assumes that the timing pointer is properly adjusted (if adjustable) to accurately read TDC of the #1 piston.

This basic procedure will work for all the 2/3/4/6 cylinder inlines from 1960 to 1988. It's not for the newer 3 and 4 cylinder loopers.

Engine off

Disconnect throttle cable

Pull throttle arm to full throttle and verify carbs open fully. Adjust main throttle stop so that the carbs are JUST hitting thier own little throttle stops. The idea here is that you want the screw stop and NOT the carbs acting as the "final stop" for your throttle lever.

Return the throttle to idle, carbs should be closed. Set all idle screws to 1 3/4 turns out from lightly seated.

Remove all plugs except #1, hook a timing light to #1. Then follow the narritive.

When the throttle is in the idle position the carbs should be fully closed and the ignition retarded. It is the amount of retardation that determines your idle speed and is set later with the idle stop screw.

Timing Event One - throttle pickup.
As the throttle is advanced, the spark timing advances toward TDC and then to before TDC. As the timing is just passing TDC the 1st (minor)throttle pickup should hit and start to open the carbs. Use the timing light. Adjust the tang or trigger screw to make this a reality. All of them are speced different, but if the 1st pickup hits at 3-4 degrees BTDC advance - you win. Use the timing light with a friend cranking it to complete this setting.

Timing Event Two - max advance.
As you continue to advance the throttle the timing will advance while the carbs slowly open a bit more. The next adjustment is max advance, this is the point where the distibutor (or trigger) can advance no more. Set the max-advance stop to 21 degrees for "direct charge" crossflow inlines and 34 degrees for the older plain vanilla crossflows. Use the light, - err to the side of caution.

Right after max advance, further throttle motion should cause the second throttle pickup to hit and open the carbs to full. You already set that -now verify it.

Leave the throttle cable disconnected and go to the water. Leave the boat strapped to the trailer and back it in so it's deep enought to run. Have a friend crank it while you operate the choke and throttle. Warm it up at 1500 rpms's.

When "warm" adjust the idle stop screw for about 800 rpm and then ajust your idle needle(s) in (one at a time) till the motor stumbles. Quickly backing it out 1/2 turn from "stumble" will usually save it from needing a re-start. Do that for all the idle screws. Re-set idle stop for 800.

Now have your friend put it in gear (make SURE you are on the transom NOT in the water) and reset your idle stop for as low as you can get it. 500-600rpm is great if your old reeds will let it idle that low in gear. Now, re-adjust the idle screws, in to stumble, then 1/2 turn out. When you've gone back and forth with that a few times and have it "perfect" - adjust each one out 1/4 turn.

Reset the idle stop so that it's about 700-800 out of gear and 500-600 in gear. Sometimes bad reeds won't let you get that low, you've GOT to get it under 1000 in neutral (worst case) to avoid beating up your lower unit when you shift into gear, even 1000 is "bad" but like I said "worst case".

Now adjust (and hook up)the throttle cable so that with the shifter in neutral, there is light to moderate pressure holding the throttle arm against the idle stop.

Take the boat off the trailer and go out in the water. Try the hole shot. If it falls on it's face try adjusting the idle screws out 1/4 turn at a time (all of them together) till you can get a hole shot. You can kind of do this on the trailer at the ramp, but it's not really safe for you, the boat, or the tow vehicle.

You're done.

-W

 

[Chris1956]

Ziggleman posted a very good procedure written by an inline expert. The only thing I can add is that you need to make sure your shift cable is adjusted properly. Set the throttle handle to neutral. Spin the prop an make sure it is in neutral. She should spin free in both directions. Now disconnect the throttle cable and the shift cable from the engine. Stick you finger into the shift slider and center it in the neutral detent. Adjust the shift cable barrel nut to fit the shift cable to the shift slide, without disturbing the position of the shift slider.

 

[ziggieman]

Thanks Chris1956 im gonna try these procedures today and ill post my progress later on . This could possibly be my problem because I never unhooked the shift cable before making any adjustments in the past ..... you guys are the best .

 

[ziggieman]

All plugs are out , dial indicator installed , when i reach TDC , the pointer is nowhere near the.464 mark . How do i make this adjustment ? Chris1956

 

[Chris1956]

Zig, from your description, you are setting the timing pointer incorrectly. Set the motor to TDC. Zero the dial pointer. Now back-off the flywheel (CCW), until the dial pointer reads .464 inches BTDC. Now look at the TDC indicator on the timing pointer. It should indicate .464" on the timing decal. If not, adjust the timing pointer to read .464".