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Originally Posted by BDiggity
(Post 3933374)
My engines do the same thing. always idle well on trailer but when in water, seem to die frequently. Makes docking a challenge when restarting engines every 30 seconds. i have adjusted the idle speed screw but dont think i should take it any higher. i will look at adjusting other aspects of the carb (Dom 1050) based on thread suggestions.
It is a carb adjustment issue. Most likely the air bleed screws need adjusted. The easiest way I found to do it was 4 corner tie the boat in a slip and adjust all the air bleed screws about 1/4 turn at time. Then try putting it in gear after each adjustment. |
Originally Posted by Griff
(Post 3933705)
How high do you have idle rpms??? Your engines should idle fine at 850rpms and then drop to about 750-800 in gear.
It is a carb adjustment issue. Most likely the air bleed screws need adjusted. The easiest way I found to do it was 4 corner tie the boat in a slip and adjust all the air bleed screws about 1/4 turn at time. Then try putting it in gear after each adjustment. |
we had some 588s tall decks built for are 32 fountain with 1150s carbs ran fine when tested when in water hard time idling sent carbs out to jessy bigs did away with power valves open up the air bleeds works alot better timing has alot to do with it liter srings help to.
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Basically, you only need to mess with idle bleeds if
You have to back the mixture screws out more than say 2.5 turns (to get enough air/fuel to idle properly) in which you would decrease bleed size, OR you have them turned in almost all the way and its still too much air/fuel, in which you would increase bleed size. Most think by backing the mixture screws out your simply adding more fuel. This is incorrect. You are adding ''more" of a predetermined mixture of air/fuel combination. The mixture is emulsified, by the air bleeds. Going smaller on the bleed, will richen that mixture, and going larger will lean that mixture (allow more air). As we know, basically when the load on the engine increases, say to accelerate the boat, the engine demands more air and fuel. Not just one or the other. Its basically the same at idle speed, just on a smaller scale. It doesn't take much air/fuel to idle the engine unloaded, but it will take more to idle it under load. The reason the engine may stall when shifted into gear, is because it simply isn't getting enough air/fuel to feed the demand. It would be like covering the carb with your hands, choking it off from air, making it stall. Hence, why I said in the beginning, before changing ignition, chasing shift switches, and other things, make sure the carb is setup properly. Just because it idles fine in neutral at 1000rpm, doesn't mean its dialed in. As its been stated earlier, do not make the mistake of cranking the idle speed screw up to compensate for this issue. What happens is, the carb will no longer soley function on the idle circuit like it was designed to, if the throttle blades are open to far. At that point, it may be pulling a bit of air/fuel from the idle circuit, air past the throttle blades, leaning it out even further. Next thing you know you have a engine that idles in neutral at 1300rpm, and 400rpm in gear. |
Originally Posted by BDiggity
(Post 3933709)
About 1000-1100 or so when neutral i think. But they drop to around 500 in gear. only used the boat 2x last year so i got thru it, but have more weekends reserved this year & want to have it running better.
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Originally Posted by 28Eliminator
(Post 3933127)
You have to take the carb off to check the transfer slots, but if the throttle plates are to far open, your idle mixture screws don't really work. If the 850 has only front idle screws and the front plates are opening up the slots all the way to make it idle, then you need to pull the carb and adjust the small screw on the secondaries (on the base plate pointing up) to open the secondaries up more so it will idle higer, then adjust the the front plates back down and adjust the idle screws. It's a little tough to explain, but the results pay off
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Originally Posted by MILD THUNDER
(Post 3932227)
Couple of things you have to keep in mind.
Dyno is not loading the engine at idle. With certain gears/prop combo, the engine can be loaded pretty hard at idle speed. Many times the guy tuning the carb will search for that "clean" idle, by turning the mixture screws in, and that works just fine in a car most of the time. Boats are different. Certain things can help this situation. Proper carb tuning More timing advance at idle (must make changes to ignition system via a different module, springs, or whatever your setup is, cant just turn distributor) Heavy flywheel (lightweight flywheels can amplify the issue, as there isn't enough momentum to keep engine turning when shifting) Prop aerator If your near the boat, go turn your idle mix screws in, counting the number of turns until they seat...and report back to what you have. |
Originally Posted by Fountain Family
(Post 3935273)
1.5 turns out.
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Originally Posted by MILD THUNDER
(Post 3935283)
Ok, try backing them out 1/2 or 3/4 turn each, for 2 turns out total. see if that helps.
Anything else I should do while I'm there? |
I would like to see the cam spec card,have seen many times as being an idle in gear problem.also as much timing at idle as possible ,shoot for 16 degrees
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