High Idle, Cannot retard /change timing to change RPM

Canufixit2

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May 20, 2016
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I've spent some time searching for this issue on line with no findings ....

Background ... 1997 Merc 2 cycle 60hp was running great for the past 2 years - left in water/did nto start for 1 week. On next usage Starts hard, Idle too high (1800 - 2000 RPM) runs rough.

Suspected Water in the 1/4 tank of Gas - used water detector past - no water. Added Dry gas and 10 gallons fresh Gas Just in case, no change.

Thought it might be Vacuum leak - found none visual and soaked the carbs outsides, gaskets and hoses with starting fluid - no change in RPM/roughness - so vacuum leak is not suspected. Throttle plates in carbs (3) all fully closed and still runs high RPMS.

Checked Plugs and spark - Plugs look ok but a little wet - changed them.

Spark is apparent to all cylinders.

Checked Compression - all the same (3 cylinders).


I'm Focusing on high idle. I marked, then moved the trigger plate about 20 deg - with no change in RPM.

I "Think" the timing is not changing. It does not appear that rotation of the trigger plate does not change RPM. So ... I expect it to be the Trigger plate or the Switch box. Since the Trigger plate is just a set up pick up coils (In my opinion?) and the switch boxes are known to fail I've ordered a new switch box.

I'm thinking that the trigger must be working or it would not even know when to fire close enough to start. Tuesday I'll get the switchbox and swap it out.

Any Suggestions?? If it still fails I'm leaning towards pulling the flywheel and changing the trigger.

Any help/comments/suggestions appreciated.
 

Canufixit2

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May 20, 2016
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Ok, I've ordered a new switchbox. Hopefully here by Monday. I'll do a quick couple measurements on the Stator and Trigger wiring and If I see nothing wrong - I'll swap it out. Hopefully I'm right. The trigger and Stators, from what I believe, are just sensing coils and rarely fail. My wallet will be the deciding factor I guess .... I'll advise regardless.
 

Canufixit2

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Switchbox (Ignition module) arrived. Prior to changing I checked the Trigger per the manual with a Ohmmeter. It is within spec. Swapped out the Switch box. No real change. High Idle a little rough. Took it for a short ride. Runs rough and does not want to rev up easily.

After changing the switch box I again moved the trigger slightly cw/ccw as the normal play allowed - no change in RPM at idle. Nothing.

I'll think this over and decide my next move. Timing light next at ilde and see if t moves when I move the trigger plate - but I'll have to wait for an etra pair of hands. Also considering pulling the Carb bowl side plug to flush with some gum out. (Thinking of sticking floats ....)

Suggestions?
 

flyingscott

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I would check the carb linkages maybe get a manual and make sure the link and sync is correct. Your throttle cable could be out of adjustment.
 

Canufixit2

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Thanks, Checked those. I disconnected the throttle cable and throttle plates are all tightly shut.

I also just pulled the carb bowl plugs, drained them and squirted in come carb cleaner in the bowl and in the carb throat. (Thinking of a sticky Float). Restarted and tapped on the carb bowls as well. no change.
 

Canufixit2

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I've read that the voltage rectifier can raise hell with the Switchbox if it starts to fail. Have one coming in Weds PM. I'll swap it out and try that.
I'll advise.
 

Canufixit2

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UP date. Still waiting for the Rectifier. I did get help in checking the timing. The timing DOES move when I move the trigger plate.by a few degrees but does not change engine RPM ?? Running at rough idle it's at 6deg ATDC. moving the trigger slightly does cause the timing to move a few degrees advance and retard. When running the engine up to a high idle I can then move the trigger much more. At high Idle (guess 3K) the timing is at TDC and even if I retard the timing by 10 degrees (to 10d ATDC) rpm is not noticeable changed? What?? To me thins proves the trigger plate is working and the Switch box is changing the timing. But it does not appear to change the rpm by any noticeable degree???

I'm going to re check for vacuum leaks with some starting fluid/wd40 and re check the reed valve plate bolts.

As stated - I have the new voltage regulator arriving in a day or to - and perhaps that's affecting the spark quality.

ANY inputs welcomed ....
 

Canufixit2

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Hi,

To Re summarize where I am ......

I Can really, Really use some help on this one. I'm a overall decent mechanic but this has me stumped. Hopefully someone can assist me?? Any Suggestions are most appreciated.


Background; I have a dock space so the Pontoon boats is in the water all year. Was Running like a top for the last couple years and started and ran Great this Spring. Due to the weather IT was not used /Started for a week. It Was running great - now starts runs rough and very high Idle - 1500 to 1800 RPMS. Will Run in a test drive but very rough and will not reach 5000 RPM (Was 5500 WOT)

1996 Merc 60 HP 3 Cyl Looks to have moderate usage. Bought a couple years ago.


I've done/checked/eliminated the following (not in this exact order);


- No water in Fuel 1/4 Tank. No recent fuel before issue. Had Run over 1/2 Tank of same fuel with no issues Checked for water in fuel with Test paste on test stick. Added Dry gas and 10 Gal fresh fuel from a fairly new and different Gas Station. Changed Engine Fuel Filter. Primer bulb is firm. I Don't believe this is fuel related.

- Then checked Idle setting, Removed Throttle linkage, ALL Throttle plates CLOSED. Linkage and and adjustments will NOT let it Idle down. Moving of Trigger plate will NOT change/ Lower Idle RPM (see below). I see nothing wrong with the linkage, etc. I believe this is OK as well.

- Pulled plugs - Looked OK. Maybe not completely dry. Changed Plugs, Checked Compression All cylinders within 1 PSI and over 96 PSI (Gauge was ancient - but repeatable). All this looked OK was well. Can pull each plug wire one at a time and engine still runs albeit not much change in rough running.

- Thought it may be the Switch box - Changed with MERC New OEM - no change.

- Put on a timing light - at Idle it's at 6 deg ATDC. If I move the Trigger plate - IT does change Timing. It does NOT change the RPMS. IF I idle up to high idle (allowing me to move the trigger plate more) Timing changes to TDC and I can retard to 10Deg ATDC and still NO RPM /CHANGE. Trigger checked with Ohm Meter - tests right in Spec. So Trigger and Timing advance seem to be working OK. I was not so concerned with the timing settings - just the fact that the timing does change with movement of the trigger plate.

- OK Vacuum leak was early suspected as well. Visual looked OK. Nuts tight on Carbs and Reed plates. Pinched off all vacuum lines at Each ends and center of hose. No change. Still always at High Idle. Sprayed with Starting fluid on all hoses, around carbs and gaskets and best possible under flywheel (to check shaft seal). At one point I did get a reduction in RPM but I was spraying so much at the sides on the Carbs - I believe it was getting sucked in the carbs. SO I repeated this with WD40 and it did not repeat. If there is a vacuum leak it's not apparent, fairly large, and occurred very quickly.

So where I am Now? Still same issue. Lots of stuff checked. I see two possible issues to follow up.

- I have read that the Voltage rectifier - if it starts going bad - can cause problems with the Switchbox and ignition. Rectifier was changed (oem) about 2 years ago (to fix charging and Tach issues) but otherwise seems OK. I can try changing this as a long shot. I have a CDI on order.

- Back to basics - It still acting like a Vacuum leak. I'm leaning towards the the top crankshaft seal going bad. I have a seal on order along with the crankshaft puller. Can this seal be changed by pull out push in once it is accessible?? (I;m assuming looking at the Seal and PArts diagrams that you do ?NOT have to split the case to change the seal?)

Well - A lot checked. IT's still idling rough and way to high and cannot lower RPM via adjustments or timing changes.

Any suggestion PLEASE ???

Thanks for reading - SteveC
 

Canufixit2

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Update - I changed the Rectifier - no change. Checked fuel tank (clean), changed tank/primer/hose to engine - not that I thought this was the issue - but a little PM for an old hose.

I've tried to find any vacuum leak with starting spray, WD40, and propane form my soldering tank. No change/luck. I would think that a Vacuum leak would affect the running less at higher RPM. Since it's running poorly at 4K+ RPM I think it's not crank seal.

I held a small delicate leaf in front of each Carburetor Intake while running. All pulling into engine - none pushing the leaf away (as a crude check on the reed valves). I'n ruling out the Reed valves - but I'll focus on the fuel delivery for now.

Well, It still runs rough and will not idle down (1200 to 2000 RPM). I Still think it's a lean fuel problem - and since it running rough at high RPM I'm thinking it's the Carbs (Blocked Jet(s) ?, Sticking Float, etc. ).


I've run a half tank of fuel with Gumout and it's still same old.

Next Plans - Re pull plugs to see If I can Id the which Carb.
Pull off Carb fuel line - - drain carbs, fill with Gumout. Pull out low speed jets and blow out with Carb cleaner and replace. Let it sit overnight.

If this fails - I'll pull and clean the 3 the carbs and "hopefully" be able to see if a reed valve is open or missing.

In the meantime - It's in the water and I'll tinker and advise.
 

Canufixit2

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update -
- Re pull plugs to see If I can Id the which Carb. - all look ok and same

Pulled off Carb fuel line - - drain carbs, blew out vent, low speed jet, in carb throat tube, then filled with Gum out. Let it sit 24 hrs. Restarted right up 2nd try. Same old. High idle and a little rough. Adjusting low speed jets to 1 1/4 turns out (where they were) no change. Tried +/- half turn - no noticeable diff. left at 1 1/2 turns out to get rpms back where they were (still 1500 RPMS +).

Ready to run the boat for a bit - then my change coils + wires and re try ... Cheap to eliminate these. Previously Trigger movement did change Timing when moved - and timing was ok but did not change idle. Trigger ohmed out to specs. Maybe an intermittent trigger?

Thoughts?
 

Canufixit2

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Can a misfiring / bad coil cause the engine to increase RPM at Idle??

Can a misfiring / bad coil cause the engine to increase RPM at Idle?? 1996 60hp MErc
 

Faztbullet

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Mar 2, 2008
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15,589
Possibly....did you index flywheel and check cylinder firing? Have you checked the flywheel key???
 

Faztbullet

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Mar 2, 2008
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Noooo.....did you index flywheel and check timing on each cylinder???? To index remove all 3 plugs, bring each cylinder to TDC and mark flywheel at pointer,reinstall plugs and take timing lite and see if they are firing at right time or double firing.
 

Canufixit2

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No I did Not. I will put this in queue to perform. Since the Trigger ohmed out OK and I replaced the switch box, and check ed cyl 1 timing I assumed it would fall into line. I'm waiting on new wires - new coils I have. I'll swap those first then continue more testing (including a DVA test of the Trigger).
 

Canufixit2

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Update - changes all three coils and plug wires - no change - I'll keep trying ...
 

Canufixit2

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Update - Changed all three coils and plug wires - no change. I'll keep trying.
 

GA_Boater

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Merged both of your threads since you are making the same post in both threads and they are on the same problem.
 

Canufixit2

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SOLVED/ FIXED ! Ii was the Stator or the Trigger.

Although I did Ohm test the Trigger Early on, (which tested OK) I finally decided to pull the Flywheel. I changed the Both the Trigger and the Stator.. The top crank seal looked fine and no sign of fuel/air/exhaust leakage - but while I was there I changed it as well. Reset idle timing. Did some final link and sync/idle/low speed jet tweaking - runs like new! I will re ohm check the Stator and Trigger on the bench and IF I fined any bad readings to indicate which item actually was bad - I'll add another post.

Quick history summary for anyone searching for this issue;

Mercury 1996 60 HP ELPTO Engine. Was running just fine/OK . Left to sit in water for almost a week. Cranking was harder and labored. Did start and idle but missing and very rough. Could NOT adjust idle to go under 1500 RPMs. Ran overall VERY rough at any speed.. Would not exceed 4K RPM. Throttle response was much different that normal - (not very responsive to throttle changes) .

Issue found - Although trigger ohmed out OK it was changed (with a new OEM) along with a new Stator (CDI). Not sure which was the problem . Issue fixed.

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