Mercruiser timing procedure

I have a 2005 3.0l mercruiser

I have a 2005 3.0l mercruiser i am having trouble with the engine running on i tried adjusting the timing without having all the information. I now know i have to bridge out the two white wires on the distributor but the instructions also say to bypass the shift interupt switch at the shift interupt switch & temporarily join together. Can anyone tell me where i will find the shift interupt switch & how do i join them.? Thanks Wayne

"With the uneven burning trait

"With the uneven burning traits of unleaded fuel,this is soooo common. Just shut it off while it is in gear. This will lower the rpm's just enough. Works for me."

Thanks Carl Sounds like the ea

Thanks Carl Sounds like the easiest solution to a common problem Thanks again

Carl:

"Just shut it off

Carl:

"Just shut it off while it is in gear."

Isn't that just masking the problem(s)? Perhaps the carb float is off adjustment causing the runon. Poor timing will definitely cause runon. Carbon deposits in the combustion chamber is another issue. Solve the problem.

"An idle speed set too high is

"An idle speed set too high is a common cause of run on or dieseling. If there are no other issues and everything is functioning properly and adjusted according to specs, a switch to a higher octane fuel will usually eliminate the problem. As Gary pointed out, any carburetor problems which cause excess fuel delivery, or timing set incorrectly will also result in "run on"."

"Actually, and IMOO here......

"Actually, and IMOO here...... it's more of a too lean fuel/air mixture (along with high cylinder temperature, etc.) that makes a perfect environment for dieseling or run-on of a marine gasser.... particularly this GM 3.0L!
This "run-on" or "dieseling" is a common problem for the 3.0L. However, I believe that it has little to do with ignition timing. Has much more to do with engine design, idle RPM and fuel/air mixture at low RPM (as noted; Too Lean).

Work with yours, and you'll at least get rid of a portion of the problem.
Some also have good luck allowing the engine to idle for a minute prior to shut down.
And yes.... the Higher Octane rated fuel will help immensely.

The ultimate cure would be TBI, or a carburetor with an electric "step down" solenoid to reduce throttle opening simultaneously as the ignition is being cut! (remember the "step UP" solenoids for Air Conditioning compressor operation? Well, a reverse scenario of that, for example! )

So far, neither Mercruiser or GM has been willing or able to figure this out! (Is the lamp un-plugged? )"

"Here's an example of what

"Here's an example of what has worked for years in the manufacture of gasoline Marine Generator carburetors. (subject; dieseling/run on)

A marine generator is shut down while operating at full RPM, full engine temperature.... agreed? (for most of us, this would be a recipe for dieseling, right!)

The main fuel circuit, along with throttle plate position, controls engine RPM via the engine RPM Governor.

While these normally DO NOT idle, they do have an idle circuit. This idle circuit also picks up fuel through the main jet.

The main jet is equipped with solenoid operated needle type valve for complete shut down of ALL fuel delivery as to totally eliminate any dieseling while being shut down at full rpm.

Merc has their own and uniquely designed carburetor for this 3.0L engine, right?
Why don't they re-design it?

This comes up all too often (on the BOC forum! Lots of 3.0L there) Wish there was an easier resolve and one that M/C would take care of...... and not dump this on the owner.

OK, I'm off my soap box now!"

"General Motors did figure out

"General Motors did figure out the dieseling problem back in the seventies and early eighties and I can remember setting idle speeds by turning the brass plunger on the solenoid. If the solenoid malfunctioned, the engine would stall at idle due to the throttle plates being completely closed. I remember the air conditioning solenoids but this was a separate solenoid used only for anti-dieseling on engine/carburetor combinations which were prone to this condition. As for the lamp being unplugged at general motors. unfortunately it appears it has been unplugged for a long time....hope they can get their act together."

"Bob, I was remembering that t

"Bob, I was remembering that the step-up solenoid was to raise RPM during the cycling ON of the freon compressor. Yes/No?
Point being.... something of the oposite design could be used for dieseling on these little 3.0L engines!
IOW's, an electrically controlled "Step-Down" device during engine shut down.
(close that throttle plate completely, and they will not diesel on us)

Anyway.... always an interesting topic.... and I too hope they can get it together. And soon."

"Ricardo, I am familiar with t

"Ricardo, I am familiar with the A/C solenoids but as I remember, some engines used them even when not equipped with A/C. I seem to remember the buick V6 as one example. I also seem to remember some early quadrajets with two solenoids....one for A/C idle speed and another for regular idle speed. They did some strange things in those days to meet emissions and driveability standards. I have added a link to the NAPA catolog where some of them are pictured...they could easily be adapted to any carburetor but really shouldn't be neccessary. A malfunctioning choke would also prevent the fast idle cam from dropping down and cause run on. An interesting story as to octane...Many years ago we experimented with an old Chevy V8 to see if it would run on coleman lantern fuel...It idled fine but even the slightest crack of the throttle produced extreme detonation. Turning the key to the "off" position wasn't stopping the engine. It seemed like it would "run on" forever. We also tried the coleman fuel in a lawnmower(lower compression ratio) and although it didn't "run on", you could hear the detonation whenever it was pushed into high grass and the governor opened the throttle. I guess we had too much time on our hands back then!
http://www.napaonline.com/NOLPPSE/(S(twa50w55izasl445okdgbs45))/Results.aspx?Ntt=idle%20solenoid&Nao=0&Nty=1&N=0&N tk=Keyword"

"Well, I'm getting us all

"Well, I'm getting us all side tracked here, but yes... I deem "Detonation" as being a gas marine engine's worst enemy.
I'm known for being the "Quench Effect" NAZI on the forum where I regularly participate re; marine related tech questions, etc.
However, while this is "run-on" is basically detonation, what I mention above is somewhat more related to full power detonation.... particularly the SBC marine engine built with the use of small chamber heads and dished pistons.
Don't get me started!

But back to the GM 3.0L..... Many do not fully understand this "run-on" and why it occurs.
But we've mostly covered that already.

."