Engine wont idle |
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firemandave
Newbie Joined: May-19-2008 Location: United States Status: Offline Points: 8 |
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Posted: September-13-2008 at 5:53pm |
I have a 92 SN with a 351 and a Holly 4bbl. The engine runs fine at cruising speed but then dies when you throttle down to a slow speed or idle. Then it is hard to start unless you throttle up right after it fires. Any thoughts? Its really tough to dock at a fast speed!!
Dave |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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Dave, How many hours since a tune up? How many hours total?
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firemandave
Newbie Joined: May-19-2008 Location: United States Status: Offline Points: 8 |
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I tuned up the engine tis spring and there is only 364 hours on the boat.
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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Did the engine run better after the tune up? Was the bad idle the reason for the tune up? Did you check the timing when you did the tune up? How about the mechanical advance? They get rusted up sometimes and need some lube. If not ether of these, then you'll need to look into the carb. I'm not the best with carbs but there are plenty here on site that are. I'm sure if you wait a day you'll get someone to give some advice. |
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Sam B
Senior Member Joined: November-17-2007 Location: StevensPoint WI Status: Offline Points: 393 |
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Check the adjustment of your idle mixture screws.
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dkjbama
Newbie Joined: August-20-2008 Location: United States Status: Offline Points: 19 |
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The carburetor: is it a holley 4010 or a 4160? You can tell by the way its constructed. On the 4010, the entire top of the carb is one piece and it covers the bowls as well. On the 4160, the bowls are screwed into the side.
Examples: This is a 4010: and this is a 4160 If you do have the 4010, be aware that these carbs are known to have poor idle quality, oftentimes called a hot stall. They were used by PCM on 351s for a couple years in the early 90s. My boat came with the 4010 and even after full remanufacturing by the holley customshop, it still wouldn't idle well once got warm under the motor box. Hope this helps. Cheers, DKJ |
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Tim D
Grand Poobah Joined: August-23-2004 Location: United States Status: Offline Points: 2635 |
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Spray some carb cleaner down each side of the intake and see if you have a leak. If it idles up, you found the leak.
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Tim D
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firemandave
Newbie Joined: May-19-2008 Location: United States Status: Offline Points: 8 |
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I tuned the baot up in the spring just to get it ready for the season. It has run great up until two weeks ago. I believe I have the Holly 4010, how lucky. Is there a cure to the problem besides changing out carbs? Is it possible to convert to fuel injection?
Dave |
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dkjbama
Newbie Joined: August-20-2008 Location: United States Status: Offline Points: 19 |
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Since it just started two weeks ago, I'm much less inclined to blame it on the carb. It is an expensive part and you'll probably want to try some simpler stuff before you plop down that amount of money. There have been some good suggestions here already, and I'm sure more will follow in the morning.
The poor idle and hot stall issue with my 4010 went on for years and I just dealt with it. It can be hard on a transmission though. I had the carb rebuilt several times and even went as far as shipping it off to Holley and paid $325 to have it completely stripped, replated with the original finish, and reassembled with all new parts. The top pic is the 4010 when i got it back from Holley. Looks brand new; unfortunately, when I put it back on the boat it was the same old story: crappy idle/hot-stall. I'd spent that much money so I just lived with it a couple more years. Last winter I found a thread about how bad the 4010 was; if I remember right, it was on this forum. I took a chance and bought the 4160 from Summit. Just WOW; what a difference. Now I crank the cold engine and hold it at about 1k RPM for about 30 secs and then drop to idle. The boat just sits there and idles, that was amazing to me. Then just put it in gear and it goes at 500 or so RPM without any further input to the throttle. For the rest of the day, it's just turn the key to crank, put it in gear, and it goes. No coughs or sputters; no more feathering and blipping the the throttle just to get the dang thing going without it stalling out. The sad part is that I'm so amazed that my boat actually runs like it should. I don't think I could tell a difference between the new carb and efi except for the starting procedure and somewhat better fuel economy. I'm not saying the carb is definitely your problem, it could very well be something simple. I just wanted to share my experience and thought it might be relevant here. I see very little reason to spend a lot of money to retrofit EFI to an older boat. A properly functioning carb can do the job nearly as well as EFI with a lot less cost and complexity. Dave, what all did your spring tune up include? Improper timing can screw up the idle as well. Weak voltage at the coil can also cause this. With the ignition on, check the voltage on the post of the ballast resistor that is NOT connected to the coil and compare it to the voltage at the battery. Do the same with the engine running. It's late... not sure if any of this makes sense. L8R, DKJ |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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Dave, You do not want to do a aftermarket conversion to injection. There are several threads on the guys who have tried it. I think out of the three people, one finally got it running after months of screwing with it. Another gave up and put the carb back on and the third we never heard back from!! |
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eric lavine
Grand Poobah Joined: August-13-2006 Location: United States Status: Offline Points: 13413 |
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My friend tried injection, he ended up putting the carb back on also
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"the things you own will start to own you"
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Munday
Gold Member Joined: August-17-2004 Location: United States Status: Offline Points: 538 |
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I have a 4010 on my 92 never had any problem.
When I changed my cam a couple years back,I timed the motor,and got her idling ok then set my idle screws while in gear,brought idle down to 600 in gear and reset idle screws. good luck Munday |
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If the only tool you have is a hammer,everything starts to look like a nail.
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