correct idle speed

[richardson61]

i have a 93 Searay with a 4.3 L i've heard correct idle speed should be around 600 rpm's. anything under 900 mine will die out idles best around 1000 or 1100 but afraid this is do high for shifting into gear. have done completed tune up, rebuilt carb, and adjusted timing best i could at 1000 rpm's

 

[Haut Medoc]

Re: correct idle speed

You missed something, 900 is too high, you will destroy your drive if you keep running it like that.....
Check all of the ignition stuff first, but my guess is the carb.....

 

[richardson61]

Re: correct idle speed

i've rebuilt carb, is only one adjustment screw and adjusting that seems to make little or no difference. we are having other running problems but have come back to the idle since trying to set timing properly. but the high idle has been a problem for years

 

[richardson61]

Re: correct idle speed

to correct other operating problems have replaced plugs, wires, cap, rotor, ignition module, coil, and pick up sensor

 

[searay3]

Re: correct idle speed

You don't give specific engine id or carb. There has to be at least an idle speed adjustment and mixture adjustments, usually two. What kind of carb and your timing is off if set at 1000 rpm.

 

[Gary H NC]

Re: correct idle speed

Sounds like he has the Merc Carb with the single idle mixture screw in the front..

How are you setting the idle? In the water or on the muffs?

 

[richardson61]

Re: correct idle speed

sorry, its a 4.3 L with a 2bl Merc carb with the one idle mixture screw in front. have adjusted the idle while in water. even tried Seloc instructions to adjust idle mixture screw with boat idling in gear, had preset per instructions at 1 1/2 turn out, turn additional 2 turns out with no effect

 

[richardson61]

Re: correct idle speed

i even thought my in dash tach was reading wrong so hooked up external tach and got same results

 

[searay3]

Re: correct idle speed

to see if your carb rebuild took, turn the mixture screw in, gently. It should start to die. If it has no effect the carb still has issues. If it does change, remove the throttle cable and turn the idle speed screw out while applying pressure to close the throttle plates with your hand. Could be there is something binding not allowing the plates to close properly.

 

[richardson61]

Re: correct idle speed

should it die if turned to the stop? and if it doesn't what carb issue should i be looking for? Should the plates close completly?

 

[gadget73]

Re: correct idle speed

See if the carb mounting bolts/nuts are loose. Had this happen on one of my 4bbls and it was a loose bolt causing a vacuum leak.

 

[searay3]

Re: correct idle speed

Check for a tight mount as mentioned. If you can spray carb cleaner around the base of the carb and the rpms change, you have a leak. If all is tight and the mixture screw has no effect, then you still have blocked passages in the carb. Take it completely apart and soak it in carb cleaner. the spray stuff ain't good enough. Dunk it overnight in the carb solution you get at NAPA, in a bucket, blow all passages clear with compressed air and reassemble. It is also possible the carb body has deteriorated and a rebuild may not work. It's been said its a 50 50 crap shoot on a rebuild...

 

[richardson61]

Re: correct idle speed

k, will check attaching bolts, and mixture screw. didn't soak on first rebuild just use spray and air will try soaking if all else fails. may or may not be related but did rebuilt cause was bogging down after running for awhile could this all be related?

 

[Bondo]

Re: correct idle speed

didn't soak on first rebuild just use spray and air will try soaking if all else fails. may or may not be related but did rebuilt cause was bogging down after running for awhile could this all be related?

Ayuh,... What was the general condition of the carb when you opened it up,..??

It's no doubt All fuel system related,...
I'm not sure or not as to whether it's Just the carb though...

 

[richardson61]

Re: correct idle speed

the accel pump plunger was chewed up so bits of rubber in bowl, not a lot of varnish or other debris though. Are you thinking it could be fuel pump Bond-o ?

 

[Bondo]

Re: correct idle speed

i've rebuilt carb, Are you thinking it could be fuel pump Bond-o ?

Nope,... I'm thinking you Missed some of the Idle Circuit passages....

When you screw the mixture screw in to Lightly seat it,... The motor should Stall...

 

[richardson61]

Re: correct idle speed

How do you tell where the idle circuit passages are? or just soak and clean the living dickens out of it again?

 

[krisnowicki]

Re: correct idle speed

If the plunger was chewed... maybe pieces of that rubber are inside it. Go through the carb agian and make sure you timing is on and I bet you are all set...

 

[richardson61]

Re: correct idle speed

thats my plan for this weekend, only problem with getting timing set correctly is getting it idled down to 600 rpm's without stalling

 

[richardson61]

Re: correct idle speed

rebuilt carb again soaking overnight, idle a little better. decided to check plugs and compression. top burnt off 4 of the six plugs, 0 compression on 1, 3, and 4 140 on 2 150 non 5 and 6. anyone have any ideas what could cause this and where to start looking?