SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: dm2bfree on June 15, 2009, 05:36:09 PM
-
So, I have a holly 850 carb with the choke horn milled off and to no surprise, my boat starts like sh*t!! :o The boat runs & starts no problem once it's warmed up for a minute, but now I'm trying to figure out if there is a way to get it to cold start better without having to go to another carb w/ a choke... I finally have this thing dialed in and don't really want to mess with it unless I have too.. I'm worried about moments launching in a marina or sitting in the channel (havasu) and having to floor my boat to get it started and taking off..
Do you think if I got a scoop with butterflies would help? It seems that it would make the fuel mixture richer since it cut's off some air flow at idle (which is essentially what choke does.. i think :-\ ), but since it would open up once i was on the throttle, it would be same as now with a regular scoop.. Also, would I need to re-jet my primaries since it could be partially closed until im a little ways in the throttle.. Any thoughts?
Something like this? http://www.summitracing.com/parts/SUM-G3106-1/?image=large
-
Non of my jets have ever had a choke (the engine is instanly loaded by the pump so they work like crap anyways).
You really should not have many if any issues.
I would like to see you try to set the idle mixture screws a little richer at idle and try that first, also how low are you trying to get it to idle?, with any sort of camshaft whatsoever you'll need to be up around 1000 RPM or so (in water)..
Most times I've seen people trying to get to idle at around 600 RPM, they won't do it....
GT
-
Most times I've seen people trying to get to idle at around 600 RPM, they won't do it....
GT
yeah I know! huh! Mine WILL idle at about 750-800, but when set that low, will stall out if I fully lift at speed and full throttle Need to keep it idling at about a grand to void this. (I don't, but should, I just lift gingerly. I like the rumpity rump sound in the no wake zone, childish,I know >:D).
I doubt the butterfly scoop will do anything. I have one, it's cool, but all open on the underside, so will not act like a choke (I know what you were thinking).
Richen her up, read your plugs and get the carb and timing set as good as you can, but you're not likely to get a reliable idle under say 900 or so.
Ray
Ray
-
True story I idle at 1k on the tach! I would follow gt's advice on this one
-
Just my opinion, but dont wast you time trying to get the motor to idle right on the trailer. Put it in the water and do it, set it with the normal load of the pump on the motor. Every time I get one to idle great on the trailer it will die on the water.
-
I agree with these guys but just want to add this.. If it shuts down on quick decel that means you have more of an issue than just cold start.
I believe you're running to lean too.
-
That;s mine that does that. And yeah, it's running a little lean. Needs to be looked at by someone smarter than me on these marine carbs.
Ray
-
I know everyone has a their own carb guy but I always take mine over to Jonny at Jet performance. Right now I have a mild 454 with a 750dp. When I went to look at the boat to buy it was a night-mare for the guy to start and I was scared Sh!tless it didn't blow up with all the starting fluid.
Anyway he gets as much motor info and calls you in a few days. My stuff runs like fuel injection! It always starts, idles and no black transom. No I don't get kick-backs just a happy customer and trying to help other boaters! Good luck you can pm me if you want his #
-
So, I have a holly 850 carb with the choke horn milled off and to no surprise, my boat starts like sh*t!! :o The boat runs & starts no problem once it's warmed up for a minute, but now I'm trying to figure out if there is a way to get it to cold start better without having to go to another carb w/ a choke... I finally have this thing dialed in and don't really want to mess with it unless I have too.. I'm worried about moments launching in a marina or sitting in the channel (havasu) and having to floor my boat to get it started and taking off..
Do you think if I got a scoop with butterflies would help? It seems that it would make the fuel mixture richer since it cut's off some air flow at idle (which is essentially what choke does.. i think :-\ ), but since it would open up once i was on the throttle, it would be same as now with a regular scoop.. Also, would I need to re-jet my primaries since it could be partially closed until im a little ways in the throttle.. Any thoughts?
Something like this? http://www.summitracing.com/parts/SUM-G3106-1/?image=large
Primary jets have no effect here nor does the milled air horn , you need to get a hand held vacuum guage and give me a call , needs to fatten up the idle at a minimum , but curious if the butterflys have been drilled ? and how much Cam ? how much inital timing ?
-
Figured I'd give an update on this.. Found that my tach was actually off and it was trying to idle at about 500-600 rpm.. I fattend the getting 1 size, plugs looked good and up'd the idle to just below 1000 rpm.. Purrs at first click of the key.. Thanks for help!!