OMC shift causes sub idle

[cargo pirate]

I have an 89 5.7 OMC cobra with a rochester 4 BBL.
When I shift into forward or reverse engine drops to 3-400 RPM.
Sometimes I can power out of it, sometimes it stalls.
Any ideas?

 

[Bondo]

Re: OMC shift causes sub idle

Ayuh,.... Welcome Aboard,...

That sounds like an idle circuit issue in the carb,..
But,..
I believe your boat also has the OMC ESA module which could possibly be involved...
Somebody will be along with more knowledge about it,... Hang tight....

 

[JustJason]

Re: OMC shift causes sub idle

I'd start by knowing your "in gear" idle rpms. If they are to low all sortsa bad things will happen to ya in the water. If they are to high you can damage things when shifting.

Now to correct your "in gear" idle rpms i'd start with thinking about the last time the engine had a tune up.

 

[Gary H NC]

Re: OMC shift causes sub idle

The 89 Cobra does have the ESA switches on the engine mounted shift cable bracket that may cause the issue.
I believe it should idle about 500 to 600 rpm in gear if i remember the OMC manual correct.

 

[cargo pirate]

OMC shift causes sub idle

Thanks for the responses. I do have the engine mounted ESA.
If I can power out of the sub idle in gear then I get a nice idle at 900.
Idle in neutral is 6-700.
Engine is running nicely ignition and carb tuned.
Thanks for all your help, I will investigate a new ESA.
Is there any way to sidestep/disable/build your own.
I saw a resistor/diode setup for electronic ignition but nothing for a points ignition.
I suppose it would be smart to go pointless and build my own ESA instead of getting a new ESA for mechanical ignition.
Cheers.

 

[Gary H NC]

Re: OMC shift causes sub idle

The ESA switches could be sticking....easy enough to check.
They should only work when shifting OUT of gear and not shifting into gear.

Unplug them and see if the idle straightens out.You will probably have to shut the motor off to shift back out of gear though.

When it idles too low does it sound like its missing or anything?
This sounds more like a carb or cable related problem...

 

[skier-24]

Re: OMC shift causes sub idle

Mine did this when it was new, 1992. All pivot points need to move freely and be well lubricated. Especially the triangular piece that activates the switches. Dissassembly may be required.

 

[King P.V.]

Re: OMC shift causes sub idle

You need to have the boat in the water, and adjust the shift cable/linkages/switches CORRECTLY !!!!! By the book, you can find the info somewhere...... here on this board.

 

[cr2k]

Re: OMC shift causes sub idle

Another issue is the spring becomes weak. Pull the arm loose not all the way off, just enough to get the spring ends out and spread them a bit, then put it all back together and give it a try. Be careful not to break the micro switches when you put it back together.