Mercruiser throttle problem

[brandhr]

I have a 1995 4.3L Mercruiser I/O. Was out on the bay yesterday and it was running fine. At the end of the day, it wouldn't throttle down to normal idle speed. Can't remember the RPMs but I would say it was running two or three times as fast as it should at idle. I could throttle up, but it wouldn't go all the way back down. Tried shutting it off and restarting a few times but that didn't help. It went in and out of gear and into reverse but of course there was a heck of a jerk as it went into gear--hope that didn't cause any serious damage but I ahd to get it back on the trailer.

Question--is this likely a simple fix such as greasing a cable or replacing a spring? Or something more complex? I haven't done much work on the boat myself but would like to avoid a trip back to the mech if this isn't too complex.

Thanks in advance.

 

[nrf414]

Re: Mercruiser throttle problem

I would start with checking your cables, then I would check your outdrive by draining the fluid and looking for any chunks of metal to come flying out.

If you were at 2-3x the idle speed and jerked it in gear, I would compare that to a "neutral drop" which is severly unhealthy.

 

[brandhr]

Re: Mercruiser throttle problem

Well, maybe only 1.5 times normal idle.

 

[brandhr]

Re: Mercruiser throttle problem

Any other opinions as to whether this situation may be an easy fix?

 

[jam1ej20]

Re: Mercruiser throttle problem

check your choke and carb linkages. Sounds like you're not closing up all the way. Look for broken or popped off springs. Definitely sounds like a fuel/carb situation to me.

 

[Bondo]

Re: Mercruiser throttle problem

Ayuh,... It would Help if you Looked at it,+ determine whether the throttle plate is closing, or the cable is hanging up....
Your discription doesn't lead to any Ideas, without further Observations...

 

[dlyman]

Re: Mercruiser throttle problem

If after you do as Don suggests then I would disconnect carb cable hook up the muffs and start it. If it still idles high then you know it's something else, it sound like choke maybe not opening all the way or vacumn leak maybe?

 

[brandhr]

Re: Mercruiser throttle problem

Finally had a chance to look at it. As stated in my original post, I haven't done much work on this boat myself (maintenance by checkbook) and I'm not very mechanical. Again, the engine is a MCM 4.3 LX, approx 1995 I think.

The problem appears to be with the carb. On the side of carb is stamped QuadaJet.

I noticed there was a zip tie on the linkage that was holding the choke plate full open. When I removed the zip tie, if I held the plate closed with the engine running, it would throttle down to normal idle speed. But it had to be manually held closed or it would open back up and engine would race.

Questions:

1. Why would the mech have zip tied the choke in the open position? Some sort of short cut to mask another problem?

2. Obviously this zip tie was there for some time and the boat was previously idling fine with the choke plate full open (unless one of my passengers tried to sabotage my boat in the middle of a day of fun--ha!) If it had been running OK with choke plate open, what would have changed to cause it to not idle down to normal speed?

3. Why will the choke plate not close (missing some sort of spring or a bad vacuum diaphragm?)

4. Should I give up on all things mechanical and attempt to trade this boat in for a kayak? I think I could figure out a broken paddle.

This is a great forum--thanks for all your help and patience. I have learned a lot from reading other posts and the manuals in the adult section. Obviously there are a lot of smart people who get some satisfaction out of helping stupid people like me (or maybe you just have too much time on your hands).

 

[brandhr]

Re: Mercruiser throttle problem--UPDATE

Re: Mercruiser throttle problem--UPDATE

Asked several of my friends for carb advice and they are all too young and only know fuel injection problems-- anybody have a theory on my carb issue?

 

[dlyman]

Re: Mercruiser throttle problem

Hi there are a few different types of chokes, does it have two wires coming from the out side of the carb on the choke mechanism? or is there a rod going down in the intake from the choke? it is an easy fix if you find out what kind of choke you have.

 

[brandhr]

Re: Mercruiser throttle problem

Think it's a rod but I'll try to take a look some night this week and confirm.