351-W carb? |
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boardersdad
Senior Member Joined: June-18-2013 Location: Wisconsin Status: Offline Points: 409 |
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Ok, now that is a PERFECT description of what I experienced last week on the Rochester carb on my pontoon's Mercruiser 140. I mean, exactly that pup...pup-pup... and so forth. However, oddly, in my case it was one morning with the engine cold. After messing with it for a long time (more than an hour), I came to believe that I had a combination of problems. I think I had some dirt in the carb, so I blasted it with more carb cleaner than I care to admit. Then I held the choke plate (which was closed too tightly) wide open with a screwdriver while I cranked it to pull the cleaner through. It started pup...pupping more and more then finally sort of pupped into running and then ran, with that gassy smell and the exhaust smoke, just as you describe. I ran it in neutral a little high on the rpm's, like around 2000 to 2200, for about 20 minutes; don't usually like to do that with no load. Anyway, it smoothed right out and never had the exact problem again... but... later in the trip the engine wasn't happy starting when warm. I've worked on this engine a lot over the years, and it generally starts as soon as I turn the key. But I had to grind for maybe 4 or 5 seconds when warm. I am convinced now that my problem is twofold -- the battery in that boat is 7 years old and isn't throwing her over as fast as it should, so I'll be picking up a new one. And I'm convinced the choke is misbehaving. I converted the Merc 140 over to electric choke about two years ago, so I am going to run through the choke calibration procedure when I find the time. For one thing, I noticed the choke plate is sitting fully closed when it should be cracked open a bit. Anyway, I know this isn't the same carb or engine, but the principles are pretty much universal and your pup...pup description matched exactly, so maybe this will be of some help to you. I hope you find it sooner rather than later! |
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gR@HaM
Platinum Member Joined: May-01-2012 Location: UK Status: Offline Points: 1265 |
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I too would recommend that holley book, not an expensive buy and it gives a good overview of the mechanics
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'82 Ski Tique
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racingnc
Senior Member Joined: July-14-2010 Location: Mooresville NC Status: Offline Points: 170 |
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So I have had the same problem. I just had mine rebuilt the problem with mine was the secondary butterflies were not opening when the engine was at operating temperature to compensate for the choke being open. I also found the rear floats were set high causing gas to drip out of the front jets. The other issue found was a bit of dirt in one of the jets. The boat has NEVER started so AWESOME. Sounds like a new boat starting. Hope this helps.
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nautique74
Groupie Joined: October-29-2004 Location: Georgia Status: Offline Points: 56 |
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The engine was cold had not ran it in a week. Started right up when I put it in the water. Running great, no skips or sputters. Ran about 45-minutes. Engine was hot, shut it down. I took the breather off. The choke is almost closed (about a 1/16" open). I just pushed the choke valve open with my finger. A little gas squirt, didn't touch throttle. Had to hold the choke open with my finger. No more gas, but when I remove my finger choke valve closes. I'm thinking choke problem. |
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1974 Ski Nautique
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3359 |
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yep
start with the choke see if it gets power. Then see if its grounded Then see if it has continuity If cant be corrected, loosten and rotate the choke so its open til you get a replacement. |
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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
Platinum Member Joined: January-03-2007 Location: United States Status: Offline Points: 1897 |
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Definitely the choke. Be warned if you do rotate the choke as Tom instructs, it will make your cold starting horrendous unless you manually hold the choke closed. |
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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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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21171 |
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Meh, my nicest starting boats (warm and cold) have the choke bypassed entirely.
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boardersdad
Senior Member Joined: June-18-2013 Location: Wisconsin Status: Offline Points: 409 |
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I adjusted the electric choke on our '84 SN2001 351W Holley 4160 yesterday--I disabled it. After reading your post, we're going to try going without it. Over the years the choke on my pontoon boat's Mercruiser 140 gave me nothing but trouble, so I'm going to disable that one, too. We'll see how it goes. We don't use the boats for ice fishing during the winter. |
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boardersdad
Senior Member Joined: June-18-2013 Location: Wisconsin Status: Offline Points: 409 |
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1984 SN2001
351W Ok, still having trouble with this. Last September the threads that connect the fuel line to the front bowl were leaking and found to be stripped. Found a used bowl with floats and installed it. The float adjustment looked the same as the old bowl but that was just a visual check. After that, the engine won't fire when cold unless we hold the choke plate open. Starts great when warm. Tried disabling the choke but experienced a hesitation on hole shot acceleration, never had that before. Doesn't sound like a choke issue. Now have set choke to 1/16" gap when cold. Still have to hold choke plate open and sometimes use starting fluid when cold. Electric choke opens normally. Not sure if we still have the hesitation; finally getting ready for summer. Thoughts? |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Steve, Still leaking at the fuel line fitting into the carb? |
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boardersdad
Senior Member Joined: June-18-2013 Location: Wisconsin Status: Offline Points: 409 |
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No more fuel leak. The fuel line wasn't in the best of shape after trying to get the leak to stop last Labor Day weekend. I replaced it with USCG approved soft line with an inline fuel filter, no more filter at the carb inlet.
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Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4947 |
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When you put your new bowl on, did you properly adjust the accelerator pump linkage? If you have any play there, allowing the throttles to open (even a tiny bit) without the acc pump pumping, you could get a hesitation.
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boardersdad
Senior Member Joined: June-18-2013 Location: Wisconsin Status: Offline Points: 409 |
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No, I didn't know about that. I watched the video tonight from another post. That was new to me. I think I have all the manuals, is that covered in the manual? Not home to look thru it right now.
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boardersdad
Senior Member Joined: June-18-2013 Location: Wisconsin Status: Offline Points: 409 |
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I'm going to read up on this and try to adjust it today. Question: could my not adjusting the accelerator pump linkage cause both problems... the poor cold starting (maybe not getting accelerator pump shot when pumping throttle before starting) and the hole shot hesitation? I'm thinking that might make sense.
Is there anything else I should've done when replacing the bowl? I used a new gasket. Thanks. |
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Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4947 |
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Adjusting the accelerator pump linkage is super easy. There's a nut and bolt with a spring, and you just unscrew it a little, and that opens it up a little and takes out any slack. The linkage is kind of line a see saw, with one side riding the acc pump cam, any the other side actuating the lever. The lever side has the adjustment. Holley has some great videos on YouTube.
The cold starting... not sure on that though, the acc pump lonkage would have to be waaay loose, but anything is possible. |
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Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4947 |
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The only thing is you might need two of the same size combination wrench, which not everyone has laying around. For mine it was two 3/8th.
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Jonny Quest
Grand Poobah Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 2958 |
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Current
2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
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boardersdad
Senior Member Joined: June-18-2013 Location: Wisconsin Status: Offline Points: 409 |
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Great advice, guys. I studied the videos and we went out to work on it. Pump the throttle--no squirt. Took a close look at the accelerator pump linkage and the threaded end of the bolt was hung up on the barrel housing for the fuel inlet. When my son gave it a tug with his fingers, it released. I shortened the bolt a bit to avoid it hanging up and we adjusted closed throttle and checked WOT 015 feeler gauge per the videos. Cold start now is great. Doesn't seem to hesitate any more but we'll see on the water. Pics below are before and after, posting from my phone so hope it works. Thanks for all the great input!
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Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4947 |
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Looks like you found the problem
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boardersdad
Senior Member Joined: June-18-2013 Location: Wisconsin Status: Offline Points: 409 |
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Cold starts great, but still hesitating on the water. I took off about half of the threads showing in the first pic, and as you can see in the second pic, the length of bolt below the linkage is quite a bit longer at this point. So if we tighten the nut to shorten the bolt, as long as we don't get loose play,will that make the accel pump arm move sooner? When watching the linkage, I can see the throttle linkage move just a little before the accel arm begins to move. Plan to adjust this tomorrow, Wednesday.
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Jonny Quest
Grand Poobah Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 2958 |
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Might be time for an accelerator pump rebuild. You may also try a different size squirter / nozzle. Try going larger by 3 or 4 sizes. If you have a 31, try the 35. That can also solve the bog or hesitation.
JQ |
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Current
2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
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Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4947 |
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That is likely the problem. Also though, if you have the screw opened up so much, that the actual pump lever is never able to fully return to the full start position, you're not going to get a proper pump shot either. |
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boardersdad
Senior Member Joined: June-18-2013 Location: Wisconsin Status: Offline Points: 409 |
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I think that was it, Brian. Yesterday I had the boy tighten down the nut (shorten the bolt) until the pump lever arm lost contact under the fuel bowl. Then I had him use his fingers to actuate the pump arm, to feel where the resistance of the pump just started--and then to set the bolt head to exactly that amount of stroke, as a starting point. All of this was with the engine warmed to operating temp. Then he took it out on the water and tested it. After each poor result, I had him loosen the nut (lengthen the bolt) a thread at a time. He's got it dialed in pretty darn good now--the hesitation is gone. I was going to have him do the final adjustment a quarter turn at a time, but he thinks he's right on the sweet spot now. I'm not sure how "wide" the sweet spot is in terms of turns of the nut. Thanks to all you guys! You saved a lot of frustration on our vacation. :) Steve |
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