92 Johnson over revs RPMs

[Trident]

1992 Johnson, 150 hp, j150glenc, fastrack, motor starts and idles good, but at 3500 rpm (neutral/no load), without moving the throttle, RPMs rev up and down 500 RPM, then will quickly rev up to 6000 RPM without moving the throttle from the 3500 RPM position. Twice there was a delay of the motor turning off when switched off. I replaced the power pack, the ignition coils, the spark leads, the spark plugs, the key switch. Arcing can be seen at the boots of the new ignition coil leads, and spark plug wire boot arcing across the ceramic to the metal portion of the park plug on the number one and number three cylinders. Before any of these problems started, a new fuel tank, hoses, filter and gauge was installed, the motor ran perfectly for three hours, then the problems started. I do not suspect the fuel related issue, especially with the arcing and the shut off symptom. Rec/Regulator (Battery is charging)?

[ChampioNman]

Make sure that #1 piston it at TDC and the timing marks on the fly wheel line up. You may have sheared the woodruff key on the crank shaft that keeps the flywheel synced up. Make sure the flywheel nut is tight too.

[Trident]

Thanks for the advice. The key is still in place on the shaft, the nut was very tight to get off. The slots look like new under the wheel for the timing sensor (which is new also, installed with the new power pack). How can I check the #1 piston? I may not have the required tools.

Could the rectifier/regulator be malfunctioning causing these strange electrical issues? Perhaps not rectifying completely or correctly ac to dc and causing the arcing? Or the regulator not regulating the correct voltage? The tach seems to be in sync with the RPMs. Is there a low tech way to verify the rec/reg is functioning correctly with a simple voltage meter/tools? Thanks in advance.

[ChampioNman]

Yep you can put a volt meter on the cranking battery it should show no more than 14.3 VDC running or no less than 12.6 VDC at idle. Check your battery volts before starting the motor. To verify TDC on #1 remove the spark plug, pull the kill switch and insert the eraser end of a pencil into #1 cylinder. Rotate the flywheel by hand and when the piston comes up and hits the eraser and almost pushes it out you should be very close to TDC on #1 verify it on the timing marks on the wheel. If anything was messed up I'd have to say the timer base. You sure all the carbs are tightened down on the intake almost sounds like it could be an air leak.

[overdrivecb]

trident not to highjack but you talking about high tech tools and championman telling you to use the eraser end of a pencil just cracked me up

championman does it have to be a snapon pencil or will the old standard #2 work?

it is a good idea sounds better than the screwdriver ive been using

[ELGIN]

Why would you rev the engine to 3500 in neutral??????????????

[torew]

Sounds like it is related to the spark plugs: Check the spark plugs, and check the leads. Might be a bad connection between the leads and one or two of the cables, and when it revs up it is because the connection goes "good" for some reason.

[Trident]

That is the RPM range where the motor starts to have the problem. It is out of the water and in neutral while I try to fix it. It does the same in gear in the water, but will adventually only want to stay running only in low RPMs. I've been convinced it is an ignition system problem once I discoverd the arcing, but I am starting to suspect fuel system. Last night I discovered the primer bulb did not stay firm after the motor was running. Is that normal? I have never had a problem with this motor in all its 16 years. I do not recall ever re-priming the bulb while its running to know if that could be a clue. I do not see any fuel leaking. Perhaps the VRO diaphram is wearing out?

[Trident]

Thanks...New plugs was my first low tech quick fix when the problem started (on vacation without the service manual). After I saw the arcing, I instaled new cables. I even switched the cables and plugs but the arcing stays at the #1 and #3 cylinders regardless, which led me to replace the ignition coils because the arcing was seen at the coil boots too - but still arcing. The service manual does not get into much detail about explaining the function of the rec/regulator. I gather it "rectifies" AC to DC from the stator to charge the batteries, and regulates the voltage as needed. It also caliculates the tach, but the tachometer is fine and batteries are charging. Only a wild guess at my very limited electrical knowledge, but could it be malfunctioning with the voltage regulation? I was told by an OMC parts dealer the rec/reg plays no role in how good or bad the motor is running, only with charging the battery and the tachometer function.

When it revs up, I am not moving the throttle, and it will rev to wide open if you let her go, but the throttle is at mid range position.

[ChampioNman]

The timer base acts like a distributor cap, it cuts the voltage from the stator and then adds spark advance when you are hooked to the linkage. Swap the orange leads between #1 and #3 and see if you are up and running. The small wires on the coils.

[ChampioNman]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by overdrivecb &raquo;</TD></TR><TR><TD CLASS="quote">trident not to highjack but you talking about high tech tools and championman telling you to use the eraser end of a pencil just cracked me up

championman does it have to be a snapon pencil or will the old standard #2 work?

it is a good idea sounds better than the screwdriver ive been using</TD></TR></TABLE>

Don't know why. It is cheaper than a piston stop tool and a very easy way to find TDC on any motor. Nope just use a regular #2 pencil. It gets you close.

[billnorman]

I'm not a professional mechanic but I will suggest a few things. I would be apprehensive about using the eraser thingy in case it broke off as it has a metal retainer. Wouldn't want to fish one of these out of a jug. Long as you're careful you shouldn't have a problem.
RPM is usually caused by air. It doesn't take much air to rev a motor to 6000 if it's in neutral.
ChampionNorman gives you a good clue. A leak in the crankcase seals or hose might cause fuel pump malfunctions and an RPM oscillation.
When I worked on airplanes, we always went to where the "last dummy" worked if there was a repeat problem. The fuel bulb may be sending you a message. New fuel tank, hoses, filter installed seems you should check these out, and bypass them all with a portable tank to see if this solves it. Fuel starvation will fry your motor if run under load at hi RPM.
The sparking doesn't seem to me to be the source unless your wires are all shot, especially if it is at so many different places but i am interested in what you find.

[ChampioNman]

who is ChampioNorman?

[torew]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ChampioNman &raquo;</TD></TR><TR><TD CLASS="quote"> who is ChampioNorman? </TD></TR></TABLE>

Don't know, but it is not BillNorman

[overdrivecb]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ChampioNman &raquo;</TD></TR><TR><TD CLASS="quote"> who is ChampioNorman? </TD></TR></TABLE>


championman + billnorman= champioNorman

looks like he "merged" with you

[billnorman]

Sorry for the misprint. Some of us can't speel.