Why??? Rev to take off

[sikz3]

What would cause me to have to rev up throttle in nuetral before putting into gear to prevent stalling?
'80 OMC 140 hp

 

[Don S]

Re: Why??? Rev to take off

Bad lower shift cable, or bad ESA system.

 

[79Glastron]

Re: Why??? Rev to take off

If your engine won't idle down in gear it might need to be tuned up. The engine should not stall when put into gear if the motor is in good shape and adjusted correctly. What is the current state of tune? Current idle speed?

 

[sikz3]

Re: Why??? Rev to take off

On the trailer it will engage in gear and not stall out but in the water that's what I have to do. If I let off throttle at cruise speed it will come to an idle. I am not sure of Rpms because the tach is acting up. I know the compression is good on the engine because I checked it. I have not done points and condenser. I know how to gap the points but not familiar with setting dwell.
Could the choke play any part here?

 

[Bondo]

Re: Why??? Rev to take off

Ayuh,...... What it does On the Trailer is totally irrevelant,.... 'cause it's Not Under Load.....

Do a Tune-Up,+ if that doesn't fix it,...... Rebuild the Carb.....

 

[ICEMAN]

Re: Why??? Rev to take off

I would look for a carburetor problem or a fuel pump problem. If one of the carburetors has a clogged passage in the idle circuit, then it will give you that problem. Another possibility is the fuel pump which operates off the crankcase pressure and vacuum pulses, if the diaphram inside is leaking, it could be flooding that cylinder, causing low speed not to fire. You might see a difference in the spark plug tips, indicating which cylinder is doing it, (3 tips the same, one different)

 

[Don S]

Re: Why??? Rev to take off

I would look for a carburetor problem or a fuel pump problem. If one of the carburetors has a clogged passage in the idle circuit, then it will give you that problem. Another possibility is the fuel pump which operates off the crankcase pressure and vacuum pulses, if the diaphram inside is leaking, it could be flooding that cylinder, causing low speed not to fire. You might see a difference in the spark plug tips, indicating which cylinder is doing it, (3 tips the same, one different)

Uhhhh, ICEMAN, this is the IO forum, not outboards, he has one carb, and the fuel pump is mechanical not crankcase pulse operated.

 

[sikz3]

Re: Why??? Rev to take off

Bad lower shift cable, or bad ESA system.

How could I rule this out? Should I start w/ tune-up,then carb, then shift cable and esa system. Although I am not sure what the ESA system is.
Thanks for everyones input.

 

[Don S]

Re: Why??? Rev to take off

Best thing to do is look at the shift interrupt switch and see if it's being held on too long. BUT!!!! Since you have an OMC, the ESA system only kills half the cylinders, not completely shutting off the ignition during the shift.
BUT!!! (again) if you have a poor idling engine because it needs a tuneup or carb repair, or __________ (fill in the blank) it may not keep idling when the ESA system is activated.

If, when you shift the Shift intrerupt switch stays engaged for too long (should be just part of a second) then you probably need a cable. If it works properly, who knows at this point.
When was the last time your engine had a full tuneup and compression check, and fuel filters.

 

[sikz3]

Re: Why??? Rev to take off

I bought the boat two years ago. When I got it, it would not idle. I rebuilt the carb which was in bad shape, took days in carb cleaner to get everything apart. When I got it together it did idle. I have never replaced cap, rotor, or condenser. I did change fuel filters during carb rebuild. And I have had this problem from day one. We have used this boat almost every weekend during the summer and it is a pain in the $@% continuing to have to do this everytime we go for a ride.

 

[Don S]

Re: Why??? Rev to take off

If the carb was in that bad of shape, then it probably just needs replaced. Not all carbs can be rebuilt. If passages get corroded closed, there is no way for you to clean them.
And do a tuneup.

 

[sikz3]

Re: Why??? Rev to take off

Don, If it was the lower shift cable or esa wouldn't I be having problems even when it was running on trailer?

 

[cheburashka]

Re: Why??? Rev to take off

1) You know it needs a tune up.
2) An engine in need of a tune up will have the symptoms you describe.
3) Even if there's another problem causing the same symptoms, the engine still needs a tune up. Otherwise, you'll never know if you've actually solved the problem.


I don't see why you're looking for all kinds of complicated reasons for the problem you're having when you haven't done the simplest possible things to rule them out. Tune it, buy a good marine carb off of Ebay, and try to rule those two things out as a cause of the problem. Then you can go on to worrying about lower shift cables and ESA.