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  #1   IP: 76.106.7.221
Old 09-12-2007, 11:20 PM
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No power in gear

I've just installed a new carb, which got my A4 from a no-start condition to an "idles nicely at 600 rpm" condition. However, I have zero power in drive.

I set the idle mixture at 1 1/4 turns from the full close (all the way clockwise) position for a beginning. The engine starts fine, easily gets up to 2500 rpm (though no higher) in neutral, and shows no hesitation when accelerating/decelerating.

However, when I put her in gear, either forward or reverse, I have no power. Rpms stay at around 1000 regardless of choke or throttle setting. I also smell raw gas in the exhaust.

Am I in a too-rich condition? I've looked around this site for some kind of carb setting guide, and I have the A4 manual, but all I can find is a generic instruction to warm up the engine, then adjust the idle mixture until one gets the best idle.

But how can one tell how a good idle will translate into power in gear? Are there any instructions that can guide me to the proper mixture setting for full power under way, without having to leave the slip to find out if I have the setting right?
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  #2   IP: 69.26.119.135
Old 09-13-2007, 09:48 AM
jayw jayw is offline
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Have you checked the ignition timing? You might try loosening the locking bolt at the base of the distributor, then rotate the distributor while the engine is running (can be done in gear) to the position where the engine runs at the highest RPM.
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  #3   IP: 38.118.52.41
Old 09-13-2007, 10:20 AM
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Other than the idle RPM set screw, the idle mixture is the only adjustment on your new carburetor. You might remove the flame arrester housing and observe the intake throat of your carburetor for the presence of raw fuel pouring in from above from a defective float valve.

Don
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  #4   IP: 206.230.48.34
Old 09-13-2007, 12:40 PM
tenders tenders is offline
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It's September. Is it possible you have barnacles on your prop? I know I have at least a full meal's worth and my engine won't get anywhere near up to top speed.
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  #5   IP: 63.239.69.1
Old 09-13-2007, 12:43 PM
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I'm going to adjust the idle mixture first, then have a look at the timing setting. I do fear barnacles on the prop, as I've been working on the engine for a month now, and she's been sitting. If I don't get anything out of the adjustments, I guess my next step is to get a diver to have a look at my prop.
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Old 09-15-2007, 01:24 PM
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Question about taking off the flame arrestor and looking into the carb throat for raw gas from a defective float valve: does this have to be done with the engine running, or can I just jump the oil pressure switch to turn on the fuel pump and see if fuel pours into the throat?

Do I need to work the throttle at all to test this, or am I just looking for fuel dumping into the throat when the fuel pump comes on?

Thanks!
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  #7   IP: 38.118.52.41
Old 09-16-2007, 07:23 AM
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To check for a defective (or dirty) float valve, you need only do as you suggest: operate the electric fuel pump or work the priming lever in the case of a mechanical pump, and the throttle position is irrelevant. In fact, it's somewhat better to not be running the engine for this check since a small amount of fuel from a leaky valve could easily be consumed by the engine and not be noticeable.

Don
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  #8   IP: 209.240.120.186
Old 09-16-2007, 09:32 AM
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When I purchased my boat the person who had installed the carb had not installed the small brass line from the carb air intake to, I think, the intake manifold. The result was the same as what you are experiencing. Maybe Don can elaborate.

Menno.
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  #9   IP: 76.106.7.221
Old 09-16-2007, 06:09 PM
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Well, I took off the flame arrestor, then bypassed the oil sensor switch to the fuel pump and ran it for a few seconds while I looked into the carb throat with the choke open. I didn't see any fuel at all leaking into the throat.

Then we started her up and let her run at about 1300 rpm until she was good and warm, then shut her off while I got the screwdriver on the idle adjustment screw (it's a real bad reach and I have to use a mirror to see where I'm going).

Once we got that on -- and it only took a few seconds -- we fired her back up and let her idle steady for a bit, then I leaned it out until the rpms died down, then turned it rich until the rpms came up and stopped increasing. Then I backed it back down, and back up again until I had a good midpoint where the rpms came up and stabilized.

Then I revved her up a few times and she responded instantly, no hesitation at all. No smoke in the exhaust at all, either. I set the idle rpm at 750 and we took her out to see if there was any difference in rpm under way.

There wasn't. Max rpm I could get was about 800, and about 2 mph. Everyone I've talked to agrees that a boat sits a month through August, you're gonna have barnacles all over the prop and shaft, so my next step is to get her hauled out this week and powerwashed and the prop and shaft cleaned out. That engine runs so sweet I can't believe that any idle mixture adjustments or other changes are suddenly going to get me an extra 1400 rpm. I'll bet I'm all barnacled up, and I'll find out this week.
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  #10   IP: 209.240.116.148
Old 09-16-2007, 07:56 PM
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No power in gear

When I purchased my boat with A4, the person who installed the carb did not install the small brass line from the carb air intake to the inlet manifold. In stead he installed a plug. The symptoms where identical to what you describe. If the line is in place, maybe it is restricted.

Good luck, Menno.
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  #11   IP: 76.106.7.221
Old 09-16-2007, 09:27 PM
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I don't think that's the problem. I removed that line when I replaced the carb, made sure it had no obstructions, and replaced it when I put the new carb in.

I'll double-check it though, to be sure.
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