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carb problems?

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ben View Drop Down
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    Posted: October-17-2004 at 5:30pm
Hi, I am a new boat owner,(79 Nautique) and am having problems with the engine hesitating upon acceleration when pulling wakeboarders. It feels like it is either running rich or lean.
Sometimes, usually when engine has been running for a while, it stalls when I try to accelerate, and will not start again. Everytime it does this I leave it for 15 minutes and it will fire straight up again. Does this suggest the engine flooding with petrol, if so what is the cure. I am not very mechanical unfortunately, so any help and suggestions would be much appreciated.

The engine is a Ford 351 with Holley carbs, and all the leads and the distributor is new.
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79nautique View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 79nautique Quote  Post ReplyReply Direct Link To This Post Posted: October-18-2004 at 12:28pm
You could have a problem with the float being a little to high. Depending on the type of holley it can be real easy to adjust if you have the style with the site hole on the side of the bowl otherwise it's a little trickier. Have you converted to electronic ign?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote IrishFooter Quote  Post ReplyReply Direct Link To This Post Posted: October-18-2004 at 12:32pm
Did you check the timing? When you do time the boat be certain to check the timing after the engine is not running well to eliminate an advance problem. After you TOTALLY eliminate ignition issues ie points gapped to .017, timing, wires and plugs; try to adjust the caborator. You do so by turning the idle mixture screws on each side of the carborator on the front of it. With the boat running turn one screw all the way clockwise and then open it back up until the engine idles well. Then repeat the same on the other side. If when you close down the screws, there is no change in the engines idle then you may need to clean/rebuild the carb. You may also want to check the vacuum line.
1979 Ski Nautique
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Tim D View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tim D Quote  Post ReplyReply Direct Link To This Post Posted: October-18-2004 at 4:32pm
If the float is too high, it would puff black smoke while at idle. When my boat wants to hesitate on take off it is usually the accelerator pump or the power valve. Both of these are a rubber diaphrams. If they have a hole or crack you see a solid stream of fuel shoot in the carb. The power valve is located on the metoring block (the part behind the bowl and idle screws are on the sides) and the accelerator pump is on the bottom with a arm going out to the linkage.
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ben View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ben Quote  Post ReplyReply Direct Link To This Post Posted: October-18-2004 at 9:32pm
I haven't converted to electronic ignition 79 nautique, but i am thinking of doing so. I don't get any black smoke Tim D, so does this eliminate float?
I have not checked timing Irish footer because i don't know how, so any advice on how would be appreciated.

I read somewhere about VAPOUR LOCK, and all the problems seem to relate to this, i have the same symptoms at least.
Thanks for the advice and any more help or ideas would be welcomed. I will try to test a few things out as soon as i can get to the water. Hopefully it is something simple like idle screws or timing because here in the UK mechanics who know about carbs are short on the ground.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote IrishFooter Quote  Post ReplyReply Direct Link To This Post Posted: October-19-2004 at 2:48am
Ok Ben lets try the easy stuff first. Checking the float level is a great and easy idea. The sight screws are located on the starbord side probably (assuming u have a 4150). Remove them and see that the fuel level is not above the screw hole ie fuel coming out when the screws are removed, and that the fuel is just below the holes. Do this in the water. If the level needs to be adjusted there is a screw and nut on the top of the front and back of the carb. While holding the nut with a wrench crack the screw and turn in and out to adjust the float level.
Next gap your points after inspecting their condition. They should be gapped to .017 with a feeler guage.
Now for checking the timing. You need a timing light. Relatively inexpensive and very easy to use. You have 2 leads on the light- one hooks to the number 1 cylinder (the starbord front) and the other lead hooks to a 12 volt power source. To operate you need to find the mark on the engine to time to. This on your boat should be a wire arrow that will reference the timing marks on the harmonic balancer. Next mark the appropriate time with a chalk line- should be 10 degrees. You have marked 10 degrees and hooked up your timing light- now with the engine running at 650 RPM aim the timing light at the harmonic balancer and observe the timing- the light flashes when the cylinder fires. If the light flashes when the chalk mark passes the arrow your timing is fine if not it needs to be adjusted. To do this- loosen the bolt on the bottom front of the distributor and turn the distributor slightly one direction or another to adjust the tinming until the chalk mark passes the arrow when the light flashes. Then tighten the bolt back down.
Other things to do- replace or inspect all ignition parts- cap, rotor, points and wires. It might also be helpful to just buy a tuneup kit and replace the condenser, points, cap and rotor. Or switch to electronic ignition.
Vapor lock might occur but you can eliminate this by checking your vent line. The vent line exits on the top stern port side of the boat. Sounds like a lot I know but its not really that overwhelming- I merely went into great detail. Good luck and email if none of this helps.
1979 Ski Nautique
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ben View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ben Quote  Post ReplyReply Direct Link To This Post Posted: October-19-2004 at 6:37am
Thanks Irishfooter, will try it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jameski Quote  Post ReplyReply Direct Link To This Post Posted: October-19-2004 at 8:42am
Ben, while you have your timing light connected, also check your distributor advance. After you have set your base timing (10 degrees? - maybe 6 - chech your manual), then rev your engine up to 3500RPM and watch your timing marks. The timing should gradually advance to 30-35 degrees BTDC.
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Tim D View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tim D Quote  Post ReplyReply Direct Link To This Post Posted: October-19-2004 at 4:03pm
Does your boat rev fine in neutral? And sputter when under a load such as in gear or pulling a skier? If this is the case, check the power valve and accelerator pump.
Tim D
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ben Quote  Post ReplyReply Direct Link To This Post Posted: October-19-2004 at 4:18pm
Will be fitting new distrib cap, points, condenser and leads tomorrow. Meanwhile have been reading an engine manual that i managed to get hold of and have found out that the carb is a 4160, not a 4150, so I don't have a sight hole to check the float level. However have read the manual and am sure i can check it dry method, Just remove the fuel bowl yeah? Invert it and check. While checking the leads etc I have discovered that the primary throttle shaft has movement in it. I can see a small amount of fuel displaced where it goes into the throttle body. In the manual it says to replace if worn, but looks as if I would have to strip the whole carb down to do so. ( I wouldn't attempt it myself.) Is there usually a small discharge like this from throttle shaft, and could this be causing the trouble? It only discharges briefly when i first move the operating lever. I wondered if i smeared vaseline or grease round the shaft where it seems to leak and then test drove it, this would indicate whether the shaft is the problem, i.e. the grease temporarily sealing the gap??
Sorry for the long post.
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ben View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ben Quote  Post ReplyReply Direct Link To This Post Posted: October-19-2004 at 4:22pm
Tim D, just read your post, and yes, revs good in neutral, only plays up when first pulling up wakeboarder, are the checks you mention difficult? (have not got yto that part of the manual yet!)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote IrishFooter Quote  Post ReplyReply Direct Link To This Post Posted: October-19-2004 at 6:26pm
Power valves do tend to fail in the event of a good or series of backfires. So that would be a good thing to check. And speaking of checking advance while you have the cap off, turn the rotor slightly and ensure that it snaps back to where it started from. This will eliminate a problem in the springs on your mechanical advance.
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CC 79 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CC 79 Quote  Post ReplyReply Direct Link To This Post Posted: October-19-2004 at 6:39pm
How do i check the valve IrishFooter?
( P.s. It is Ben, but i joined )
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jim_In_Houston Quote  Post ReplyReply Direct Link To This Post Posted: October-19-2004 at 9:37pm
I thought this thread was about the Atkins diet.
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