Carburetor set up help - engine stumbling while planing
06-18-2019 | 03:33 PM
#11
Registered
Joined: Sep 2009
Posts: 419
Likes: 14
From: Lake Winnipesaukee, NH
I'd adjust the floats first. Reversion off idle doesn't seem possible. But I'm no expert. However I am a person who has had some problems with it!
My understanding is you want somewhere around 12.4 AFR during acceleration and under load. Which in boats is most of the time.
The wedge idea came from some early straight drive engines i have seen. And I agree, it can't tilt you any more than running level or you will get a different problem.
Question, are these carbs normally used in a boat?
My understanding is you want somewhere around 12.4 AFR during acceleration and under load. Which in boats is most of the time.
The wedge idea came from some early straight drive engines i have seen. And I agree, it can't tilt you any more than running level or you will get a different problem.
Question, are these carbs normally used in a boat?
06-18-2019 | 03:47 PM
#12
Registered
Joined: Mar 2004
Posts: 2,696
Likes: 93
From: Pa
I’m looking for some guidance on getting my carb to function correctly.
Background: 27’ Fountain Fever, 509CI BBS, FAST dual wide band, Pro Systems Venom II carb, HP500 intake, AFR heads etc. Bravo 1 with 27pitch 5 blade.
Currently when I try to get on plane the boat coughs and stumbles. The problem occurs around 2800-3000 PRM when the boat is at maximum bow angle. The AFRs are reading ~10.7 (I’ll verify the number, going from memory here). I can push the throttle more with no increase in engine power.
Once I finally get the boat to plane out, no further problems with power. I can run to 5000 rpm, AFRs look safe. It’s only getting on plane that is a problem.
I swapped on a Holley 800 set up for an HP500 clone engine and the problem completely went away. No issues getting on plane, able to increase throttle with the bow in the air without any stumbling.
Where should I start looking in the carb? My thought is too much fuel combined with a severe angle the carb is sitting when the bow is in the air is contributing to the problem?
Background: 27’ Fountain Fever, 509CI BBS, FAST dual wide band, Pro Systems Venom II carb, HP500 intake, AFR heads etc. Bravo 1 with 27pitch 5 blade.
Currently when I try to get on plane the boat coughs and stumbles. The problem occurs around 2800-3000 PRM when the boat is at maximum bow angle. The AFRs are reading ~10.7 (I’ll verify the number, going from memory here). I can push the throttle more with no increase in engine power.
Once I finally get the boat to plane out, no further problems with power. I can run to 5000 rpm, AFRs look safe. It’s only getting on plane that is a problem.
I swapped on a Holley 800 set up for an HP500 clone engine and the problem completely went away. No issues getting on plane, able to increase throttle with the bow in the air without any stumbling.
Where should I start looking in the carb? My thought is too much fuel combined with a severe angle the carb is sitting when the bow is in the air is contributing to the problem?
06-18-2019 | 07:54 PM
#13
Thread Starter
Registered
Joined: Jun 2014
Posts: 267
Likes: 12
From: Buffalo, NY
I'd adjust the floats first. Reversion off idle doesn't seem possible. But I'm no expert. However I am a person who has had some problems with it!
My understanding is you want somewhere around 12.4 AFR during acceleration and under load. Which in boats is most of the time.
The wedge idea came from some early straight drive engines i have seen. And I agree, it can't tilt you any more than running level or you will get a different problem.
Question, are these carbs normally used in a boat?
My understanding is you want somewhere around 12.4 AFR during acceleration and under load. Which in boats is most of the time.
The wedge idea came from some early straight drive engines i have seen. And I agree, it can't tilt you any more than running level or you will get a different problem.
Question, are these carbs normally used in a boat?
That's what I'm leaning towards just to be done with this (WTB already placed) - I hate to fire the parts cannon, but I'd like to use the boat without all the drama this year.
I'll be attending the Sacandaga Fun Run this weekend, I'm sure there will be enough time to swap back to the pro systems carb and do some troubleshooting.
Ryan
Last edited by Ballistic Beak; 06-18-2019 at 07:57 PM.
06-19-2019 | 09:27 AM
#14
Registered
Joined: Jul 2004
Posts: 11,332
Likes: 73
From: chicago
Is it coughing back thru the carb? Sounds like it might be lean. Try richening up the primary idle screws. It might be having trouble getting good fuel flow from the boosters at such a high load / low speed situation
06-19-2019 | 10:08 AM
#16
Were doomed!
Joined: Oct 2000
Posts: 7,096
Likes: 1,393
From: Chicago, IL
if the AFR is 10:1 then its running way rich....sounds to me like the fuel is sloshing through the metering block vent and enriching the engine...maybe a vent extension would help in blocking the sloshing fuel from getting in when in the bow up position.......
__________________
-Wally
Money can't buy happiness, but it can buy horsepower. And I've never seen a sad person hauling a$$!
-Wally
Money can't buy happiness, but it can buy horsepower. And I've never seen a sad person hauling a$$!
06-19-2019 | 10:31 AM
#18
Registered
Joined: Jul 2004
Posts: 11,332
Likes: 73
From: chicago
During alot of trials and tabulations doing on the water carb tuning with widebands, ive had a few engines where ive seen afrs in the 10s. While yes , its rich, it has never made the engines sputter, lose tons of power, fall on their face, etc. Heck, some hot oem engines are actually tuned so they are in the 10s at wide open throttle..
i see the lean idle circuit thing alot. The carb people tell you to adjust screws for highest vacuum reading, or basically leanest setting you can get. Works great on cars, where you have an accelerator pump, or two in holleys case, to help give that burst of gasoline to get the engine revving to a speed where the airflow makes gas able to be drawn from the boosters. In a boat, the accelerator pumps become nonexistent in a getting on plane scenerio. The engine either needs gas from the boosters, or idle circuit.
He may need to adjust the high speed air bleeds if in fact its a lean condition and richening the screws dont help.
#32 is kinda big for a high speed air bleed. Id prob step down to a 28 to start
i see the lean idle circuit thing alot. The carb people tell you to adjust screws for highest vacuum reading, or basically leanest setting you can get. Works great on cars, where you have an accelerator pump, or two in holleys case, to help give that burst of gasoline to get the engine revving to a speed where the airflow makes gas able to be drawn from the boosters. In a boat, the accelerator pumps become nonexistent in a getting on plane scenerio. The engine either needs gas from the boosters, or idle circuit.
He may need to adjust the high speed air bleeds if in fact its a lean condition and richening the screws dont help.
#32 is kinda big for a high speed air bleed. Id prob step down to a 28 to start
Last edited by MILD THUNDER; 06-19-2019 at 10:34 AM.
06-19-2019 | 11:40 AM
#20
Platinum Member
Joined: Apr 2005
Posts: 2,150
Likes: 15
From: Northport N.Y.
Last edited by 14 apache; 06-19-2019 at 12:24 PM.
