how the carb works

Lawnpro979

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Aug 17, 2014
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I have the volvo penta 4.3 gl with the hollie carb. when 1st start up the rpm stays around 400. I useually give it a min to warm up. because sometimes it will die. But shouldn't the choke kick in and run this up.... now granted I've only took the boat out in warm weather.
maybe I'm missing something here. Is the carb working like it's suppose too ?

thanks
 

GA_Boater

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May 24, 2011
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Are you moving the throttle to set the choke?

Next time advance the throttle to forward and back to neutral a couple of times. That does two things, sets the choke closed and gives a shot of gas from the accelerator pump. The closed choke also increases the idle RPM until the motor warms and the choke opens.

If you're doing that already, never mind.
 

captmello

Captain
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Jun 30, 2008
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3,826
The choke may not raise the idle...give it a couple pumps like GA said, only when cold of course, then leave the throttle 1/3 open. Once the motor starts, pull the throttle back and let it idle at 1100-1200rpm to warm up.
 

Augoose

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Mar 21, 2010
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Hopefully I'll learn something here too......the Marine Holley's don't have a high/fast idle cam like older cars correct? Is the OP expecting that a boat carb acts in the same manner in that the automatic choke turns and catches the high idle cam, keeping the rpms up to about 1800 or so until the engine warms up? Then the choke adjusts back, releasing the cam and then dropping the idle back to around 600?

I'm assuming that since you can simply adjust the throttle control arm a bit, designers did away with the high idle cam?
 

skydiveD30571

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Feb 13, 2012
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Augoose, Don S explained to me that the high idle cam was done away with because most people won't let the rpm come down before slamming the drive into gear at 1000+ rpm. Not only hard on the gearing, but dangerous when around swimmers or at a dock. Having to open the throttle manually (in neutral) for a faster idle rpm means the driver will have to come back to neutral idle to shift into gear, reducing the rpm down to an acceptable level before shifting.

See this thread, especially post #8.
http://forums.iboats.com/forum/engi...oards/590366-why-do-warm-starts-need-throttle
 
Last edited:

Lawnpro979

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Aug 17, 2014
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ok.....this boat is new to me, as inboard engines..... the previous owner showed me. to pump the throttle a few time b4 starting..... then of corse return to nuteral.... I do this... but it seems that I'm NOT reaching choke.... NOW, I am expecting to have a higher idle at startup...... But not getting it.... my boat seems to idle at 3 to 400 rpm's....... it's GREAT after warm up.but will die a couple of times when 1st starting..........is this right ? thanks...
or should maybe I raise the idle at the carb ?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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you should pump it like you are doing, and then bring the throttle only (disconnect the shift by pressing the button at the base of the controls) to about 1/3 forward. then start. the motot should be running about 1200-1500 RPM. let it run there for about a minute or two, then slowly bring the throttle back.

once the motor is a bit warmed up, pull the control back to neutral to re-engage the shifter, then go boating.
 

Lou C

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Nov 10, 2002
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11,802
My 4.3 with the Rochester Quadrajet does not have the fast idle cam either. I pump it 3x and advance the throttle 1/3 fwd as stated above. After it starts at about 1500 rpm I decrease it down to 1000 and let it warm up. The choke valve and linkage needs to be cleaned with carb cleaner 1x a year. Make sure it opens all the way when the engine warms up.
 

Lawnpro979

Petty Officer 1st Class
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Aug 17, 2014
Messages
232
OK Thx Got it............. HEY guys, I'm sorry if I seem stupid, I am new to this type of boat. and I really appreciate the help
 
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