running after I turn the key off...

[aggiedave98]

I took my '88 Invader 17.5' I/O out today (3L 4cyl alpha one). Everything went great except 2 things:

1) lightening all around us and a storm coming in
2) when I would turn off the boat, a few times it would keep running after I shut the key off. The first time I turned it off, it probably ran for about 5 seconds after I shut off the key.

Any ideas? I thought I had posted this before and was told to up the octane in the gas (which makes sense I guess if it's combusting because of the pressue without spark I guess) but I looked through all my old posts and couldn't find it. I think last time I was told to use higher octane gas, which I think did help last year.

Is that it?? Shouldn't I be able to run 87 octane??

 

[Don S]

Re: running after I turn the key off...

The biggest problem with "run on" is shutting the engine off immediatly after a run. Allow it to idle for a minute or two before shutting off. Second is the idle rpm to fast.
Here is the Merc service bulletin covering the problem.

http://www.boatfix.com/merc/Bullet/97/97_17.pdf

 

[aggiedave98]

Re: running after I turn the key off...

Don,

Wow!! I don't think 5 min. went by after my post... once again, you've come to the rescue!! You are dead on...

1) thinking back, I doubt I let it idle for 1-2 min after coming to a stop
2) my idle is set high right now...

for #2, getting my idle correct is a question I've had. Normally I would set it while in the boat, but I had a had a full boat and didn't want to burden then w/ adjusting it with them in the boat...

It was idleing about 1000rpm most of the time, but at times it would idle at 1500rpm... any ideas why?? I am good at doing major repairs, etc if I can follow instructions, but setting the idle correctly has always been a challenge for me. One thing that helped is recently I was told to set it with the boat in the water with it in gear... in the past I always set it in the driveway.


Also, just because I'm curious... why does letting it idle for a while help fix the problem?? Because there's less gas flowing through??

Does higher octane gas help the issue because it's harder to ignite??

Thanks again Don!!! You've always been a HUGE help!!

 

[Don S]

Re: running after I turn the key off...

If it's idling that fast, it will always have problems shutting down. You probably need to adjust the throttle cable so it pushes the throttle linkage on the carb SLIGHTLY preloaded to the idle position. Just turn the barrel on the throttle cable to adjust it.
Best thing to do is remove the throttle cable from the carb, then adjust the idle speed when holding the throttle to idle. Then adjust the cable to fit.

 

[aggiedave98]

Re: running after I turn the key off...

Don,

I'll take a look tomorrow!!

I've owned the boat (an '89) for 6 years now and have always had a problem w/ a predictable idle (it may vary from 600rpm to 1000rpm without any adjustments let's say). Is there anything I missing or should I expect a range like that since it's a carb??

 

[Reel Poor]

Re: running after I turn the key off...

With the idle speed diference you describe (the 400 or so above your lowest idling speed) make sure that the fast idle speed cam (operated by the choke thermostat) is not sticking. If it is it wont allow the carb to return to proper idle specs.

 

[Don S]

Re: running after I turn the key off...

Marine carbs DO NOT have hi idle cams on the carb. That's an automotive setup.