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Won’t run right with flame arrestor |
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2_Nautiques 
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Joined: March-22-2006 Location: United States Status: Offline Points: 251 |
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 Topic: Won’t run right with flame arrestorPosted: August-03-2007 at 12:03pm |
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Brief history:
My 350 OMC has a mid RPM miss above 3000 RPM "previous post" WOT the miss was gone. could not find the problem. Then the carb started acting up it is a quadrajet "previous post" Nuttyskier help me out tons over the phone to take apart and find the problem. It was white scale that was causing the carb issues. Last night I finally got the boat back in the water for a sea trial after fixing the carb and also installing new cap and wires. I found that the miss was still there in the mid RPM range and WOT it was gone. So I removed the flame arrestor to see what the carb was doing during this RPM range "above 3000". Well after removing the flame arrestor, the engine ran perfect!!! No miss, Idles great! So I thought that the arrestor was plugged and throughly cleaned it. Reinstalled and the same miss comes back, remove it and the motor runs great. Whats going on? Is this something to do with float levels? Any help? |
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nuttyskier2002
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Joined: September-28-2005 Location: United States Status: Offline Points: 669 |
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Posted: August-03-2007 at 4:33pm |
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Matt, I don't recall, did your boat run correctly a year ago when you first put this carburetor on?
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95 Malibu Echelon w/Mercruiser 350 Magnum Skier
Former boats: 88 Ski Centurion Tru Trac II 59 Chris Craft Capri (woody) |
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GottaSki
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Joined: April-21-2005 Location: NE CT Status: Offline Points: 3333 |
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Posted: August-03-2007 at 4:38pm |
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How does it run if you don't tighten the FA?
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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2_Nautiques
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Posted: August-03-2007 at 4:50pm |
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Brian, I ran that boat about 1/2 hour after I bought it in the fall of 05. It ran rought and would not idle, so I just bought a rebuild carb in spring of 06 to try and save myself some grief! The boat had the miss last year so I upgraded to the electronic ignition spring 07.
Tom, I did not try to run it with FA loose? I believe that the FA is original OMC. I really believe that it is totally clean. Used a pan of gas and carb spray? |
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GottaSki
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Joined: April-21-2005 Location: NE CT Status: Offline Points: 3333 |
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Posted: August-03-2007 at 5:06pm |
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Hmm If that FA is the typical OMC 1" pancake, it may be richening the mix by causing a little vacuum above the venturies when its pulling big cfm, and your getting some plug fouling, and skipping. Check the plugs after a 30-40 seconds WOT then chop the throttle and ignition., both with the FA on and with it off. If the plugs are blackened markedly with the FA on, then its not flowing enough air..
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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2_Nautiques
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Posted: August-03-2007 at 5:21pm |
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Tom, yep it is a 1" pancake, it appears as if once the secondaries kick in the miss/skip goes away with the FA. I though about getting a taller FA, I think I have room?
If I get it back in the water this weekend, I will try to get plug check. |
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GottaSki
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Joined: April-21-2005 Location: NE CT Status: Offline Points: 3333 |
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Posted: August-03-2007 at 5:33pm |
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I was mistaken, then, do the test at the rpm that exibits the symtom, not WOT as I suggested. Since the skip appears to be on the primaries, cfm is less, and I'm less confident that this is the problem but its still a good exercise and you may discover some things.
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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backfoot100
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Joined: January-03-2007 Location: United States Status: Offline Points: 1897 |
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Posted: August-03-2007 at 5:37pm |
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This one does sound really weird. I read about and heard of turbulence around sharp corners that can affect air flow, but I've never actually seen something like this that could actually cause that. It'll be interesting to see what that plug read does. Good idea Gottaski.
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When people run down to the lake to see what's making that noise, you've succeeded.
Eddie |
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2_Nautiques
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Posted: August-03-2007 at 6:54pm |
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Thanks for the suggestions, as always I was looking for "Oh, just adjust this and your good to go" however our Ohio summer is slipping away. Should I just buy a new Holly replacement carb..I think a 4175 will replace the Quadrajet? Summit has them for $419.
I use this boat on Lake Erie and a breakdown would cost me close to that in towing service alone. I barely got it back to the dock on the last carb failure! I hate to get up yet, just considering my options. Will the FA off of my 88 351 Holly fit this carb, might be an interesting trial? |
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2_Nautiques
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Posted: August-13-2007 at 12:23pm |
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Bought a new Holly 4175 spreadbore carb from Summit and installed this weekend. I had to remove the wedge plate and install a 1" spacer block to make it fit. The fuel inlet was hitting the thermostst housing.
The motor runs great now! Idles well no hesitation and no mid RPM miss. I am still using the 1" OMC original FA. Now I have a rebuild, but not quit right, quadrajet for sale. |
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