problem solving engine trouble |
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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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Posted: July-25-2015 at 2:18pm |
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Hey everyone. I have a 76 nautique with a ford 351. The engine was completely rebuilt a couple years ago. After the rebuild, the engine ran great other than one minor problem. When I driving at a slow speed like when I was trying to pull kids skiing the engine would start sputtering and want to shut off. I would have to pump the throttle a few times to keep it running. It ran perfect at higher speeds and I didn't have any trouble accelerating or idling. I thought it was a carburetor problem and tried everything I could think of to adjust it. The carb was also rebuilt/cleaned during the engine rebuild.
Also, the carb was a holly Automobile carb so it wasn't even supposed to be on the boat. I thought that may have been the problem anyway. I wasn't sure if they were tuned differently since boats and cars are under different loads. Since that was a safety problem that needed to be fixed anyway I bought a new carb for the boat this year. It is a Quick Fuel M-600. (Here is the thread I started about that: http://www.correctcraftfan.com/forum/forum_posts.asp?TID=36281&KW=&title=where-to-buy-a-holley-carb) The QF carb install was simple. The boat fired right up and ran great in the drive way. I took it to the lake to check everything out and do some final adjustments but I was still having the same problems except this time it was trying to sputter off at slow and cruising speeds. It seemed to be idling pretty high too but I think most of that is because I needed to re-adjust the throttle cable after installing the new carb. Does anyone have any thoughts on what could be causing the engine to want to choke off when cruising? does it sound like a carb tuning issue or could there be something else going on? Thanks for your help! |
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Luke Pearson
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Jonny Quest
Grand Poobah Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 2957 |
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Your problem sounds like fuel delivery. If the carb is not getting fuel, even the world's best carb can't do its job. I would look at:
1. Fuel Pump 2. Fuel Filter and/or water separator 3. Fuel tank vent 4. Debris in the fuel tank 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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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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thanks, JQ. We cleaned the fuel tank out when we rebuilt the engine so I'm going to mark that one off the list. I also just put a new fuel filter/water separator on a couple months ago. I'm going to do some checking tomorrow to see if the fuel pump is working correctly and go from there. I'll let everyone know the progress.
How would you go about checking the fuel tank vent? |
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Luke Pearson
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Jonny Quest
Grand Poobah Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 2957 |
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Fuel tank vent prevents the fuel system from pulling vacuum when fuel is sucked out. The vent can and will plug-up. A good way to check is to remove the gas tank fill cap when running the boat If your fuel delivery symptoms disappear, then you likely have a fuel vent problem.
By pulling the fuel fill cap, you are by-passing the vent and directly venting the fuel tank. Simple and easy test. 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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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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I'm not able to replicate the problem I'm having when I'm running the engine in the driveway so i'll have to get on the water to do some of these tests.
I did just check to make sure the fuel pump was working by unplugging the coil wire, pointing the fuel line from the pump to the carb into a glass jar, and turning the engine over. The pump is shooting blasts of clean fuel directly into the carb so I'm guessing the pump is working correctly. I also don't see any debris in the fuel. I'll try to get the boat on the water as soon as possible to check the fuel tank vent. Any other ideas? Also, my throttle cable is sticky. (When I bump the rpm's up from neutral and then return the throttle to neutral the rpm's don't come back down) Is there a way to loosen up the cable or is it time to replace? Thanks. |
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Luke Pearson
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21171 |
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Sticky or improperly adjusted? More likely the latter if it's smooth otherwise.
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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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good question. Before I decided to change the carb it was acting sticky like I said in my last post. After the carb install it was improperly adjusted. When I bumped the throttle forward, the engine would rev up before it went in gear causing the boat to jump. I adjusted the cable exactly like someone mentioned in this thread: http://www.correctcraftfan.com/forum/forum_posts.asp?TID=26601&title=shift-cable-adjustment-pcm-123-and-morse
It is working fine now other than when I bump the throttle forward and then bring it back to neutral, the RPM's don't return to idle. |
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Luke Pearson
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Jonny Quest
Grand Poobah Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 2957 |
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Not returning to idle could be as simple as a throttle return spring.
On the other hand, if the carburetor is over-tightened or improperly tightened onto the intake manifold, the carb body can flex and cause the throttle plates to bind slightly. This could affect return to idle. 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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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Online Points: 3359 |
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Also, The quick released on the cable should be adjusted so it provides some light pressure to push against the idle stop every time.
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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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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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Gottaski, that may be my problem. I'll check when I get back to the boat.
Back to the engine troubleshooting, I've checked all the fuel delivery options and it seems like the carb is getting fuel like it is supposed to. I called quickfuel'd tech line and the guy I spoke with said I needed to go up a jet size. He said the m-600 comes with 67 jets and I need to go up to a 69. I also ran the boat this morning and doubled checked the float levels. They are at the recommended height. I am only getting the hesitation problem around 2000-2500 rpm. If I let the boat cruise at that speed it will stumble. If I don't touch the throttle it will stumble for a few seconds and then resume running normal. After 5-10 seconds it will stumble again and repeat. Any thoughts on any of that? I appreciate yalls help as I learn a lot of this stuff. |
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Luke Pearson
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Jonny Quest
Grand Poobah Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 2957 |
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67 jets stock? That is strange. My M-600 came with 65 jets in the Primary and 72 jets in the Secondary. It was my understanding from QF that 65/72 was the base or stock setting for sea-level. Well, as jets are relatively inexpensive, that may be a place to start. The intermittent stumble is a head-scratcher... |
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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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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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Still working on this problem. How is everyone's carburetor mounted to the manifold on their boat?
My boat is a 76 nautique with ford 351 PCM. My new Quickfuel Carb has two aluminum spacers between it and the manifold. So that makes 3 gaskets. I'm wondering if I may have a vacuum leak and these might be the culprit. The idle problem I mentioned earlier is still there after adjusting everything and I'm pretty sure my throttle cable isn't sticking. I know that a vacuum leak can cause idle problems too. I'm wondering if I need both spacers under the carb. A vacuum leak would explain a lot of the symptoms it's giving me. thoughts? |
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Luke Pearson
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Jonny Quest
Grand Poobah Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 2957 |
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2 spacers in series? That doesn't sound kosher. You could always try removing one spacer. How thick/tall is the single spacer? The 2 combined?
Be sure to use the marine carb/spacer gaskets. Thicker and stronger. http://www.skidim.com/GASKET-CARBURETOR-SPACER/productinfo/RM0054B/ 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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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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Just now getting the boat back out and starting this troubleshooting process again. The boat fired up with no problem today on the hose. Again, I'm not getting the problem on the hose; its only when the boat is under load on the water (approx 2500 rpm). I am still getting the high idle though. It's idling at 1000 rpm. I've adjusted the cable correctly so i'm 99% sure something else is causing the high idle.
The first thing I'm checking is for a vacuum leak. I throttled up to 2500 rpm and sprayed soapy water around the base of the spacer plate and carb. I'm not seeing or hearing anything that would indicate a leak. Is there anything I should be doing differently? Or a different place I should be checking? I'm also wondering about the timing. I've seen a few threads talking about how timing could also cause similar symptoms that I'm having. Has anyone found that to be true? I don't have a timing light so I'm going to try to borrow one from a friend to double check the timing. Thanks! |
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Luke Pearson
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tryathlete
Platinum Member Joined: April-19-2013 Location: Lake Villa, IL Status: Offline Points: 1797 |
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Might be good to have a timing light on to watch the advance under rpm change. It's possible the centrifugal advance is rusty and not moving outward and then snapping out as rpm increases. Lack of timing advance could explain some of your intermittent stumbling.
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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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thanks. I'll try that.
also, does anyone know of what my vacuum readings need to be? Or can point me to resources that shows how to check the vacuum properly? thanks. |
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Luke Pearson
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gun-driver
Grand Poobah Joined: July-18-2008 Location: Pittsburgh, Pa Status: Offline Points: 4127 |
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To check for a vacuum leak spray starter fluid around the base of the carb. If it is leaking it will increase rpm as it sucks in the starter fluid.
Soapy water wont find a suction leak, a pressure leak yes a suction no. |
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tryathlete
Platinum Member Joined: April-19-2013 Location: Lake Villa, IL Status: Offline Points: 1797 |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Disconnect the cable from the carb and see if you can get it to idle. Sometimes missadjustment of the cable will cause it to hold open making a high idle.
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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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should I hook up the gauge to the back of the carb or is there a better spot to do that?
Got it. I've read contradicting things about what to spray but I'll give it a shot. thanks for the advice.
good stuff. I wasn't sure if the readings would be different for cars/boats. Thanks for the link. I'll grab a gauge tomorrow and check it out.
I just tested this and it idles high when the cable is disconnected too. |
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Luke Pearson
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SNobsessed
Grand Poobah Joined: October-21-2007 Location: IA Status: Offline Points: 7102 |
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Vacuum leak could also be at intake manifold gasket to head. Unlikely, but may be worth ruling out.
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“Beer is proof that God loves us and wants us to be happy.”
Ben Franklin |
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tryathlete
Platinum Member Joined: April-19-2013 Location: Lake Villa, IL Status: Offline Points: 1797 |
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Can 'o starting fluid and vacuum gauge should help. That
Timing light would still be on my radar. Your going to find this one soon. |
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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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I wasn't able to find a leak with the starter fluid test.
Here is my vacuum reading. Also notice the hard start: vacuum reading Do you know if my engine is right or left hand rotation? '76 351 PCm My firing order right now is set up as 1 8 4 5 6 2 7 3 Timing is supposed to be set at 10* BTC. I can't even see the numbers unless I rotate the distributor which brings the RPM up above 1000. thoughts about any of this? |
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Luke Pearson
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Jonny Quest
Grand Poobah Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 2957 |
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For a "Normal Rotation" or left hand motor 1-3-7-2-6-5-4-8 is correct.
For a "Reverse Rotation" or right hand motor it is 1-8-4-5-6-2-7-3. Sounds like you are reverse rotation. Just to be sure...when sitting in the driver's seat and looking at the engine, if the engine rotates counter-clockwise then you are "Reverse Rotation". If you can't see the timing marks on the harmonic balancer, I would recommend a couple of things: 1. With coil-to-distributor wire unplugged, put a socket on your harmonic balancer and rotate to where you see the timing marks. 2. Clean up the timing marks with a rag and then color the marks in with a white crayon. Then wipe off the excess. This will let you see the timing marks much easier with a timing light. 3. Ensure that you are at Top Dead Center on #1 cylinder. Here is a short video showing you how to find TDC. 4. With the engine at TDC, look at the timing marks on the harmonic balancer. The 0 degree mark should line up with the timing pointer when the engine is at TDC. This will give you a reference starting point. If your timing marks are not visible, double check that you are at TDC on cylinder number one (1) compression stroke and not 180 degrees off on the exhaust stroke. If you still can't see the timing marks, you may need to buy some timing tape like this. Then you can re-set the timing. 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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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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Ok timing is adjusted properly so I can mark that off the list. I'm still getting a high idle (approx. 1000 rpm).
Can a bad PCV valve cause a high idle? Should it be air tight? It's loose enough I can wiggle it around and pull it right out with almost no friction. I've tried unhooking the throttle cable and loosening the idle screw on the carb. Neither will bring the idle below 1000 rpm. |
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Luke Pearson
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Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4947 |
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Hmmm, maybe the rubber gasket in the valve cover for the PCV valve is missing or totally worn out. This is a rare situation, but maybe a the PCV to valve cover gasket got lost during the rebuild. It's not normally super tight, but there should be some friction. Maybe there's the vacuum leak right there?
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SNobsessed
Grand Poobah Joined: October-21-2007 Location: IA Status: Offline Points: 7102 |
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Plug the PVC entirely, for a test. Then you will know if it is the cause.
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“Beer is proof that God loves us and wants us to be happy.”
Ben Franklin |
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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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The rubber gasket/grommet is there but it must be worn out because the PCV valve is definitely loose. It's looser than I feel like it should be anyway. Those parts are so cheap I may just order them anyway.
Might be a dumb question but should I plug both the port going into the carb spacer as well as the hole where the PCV valve sits? |
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Luke Pearson
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tryathlete
Platinum Member Joined: April-19-2013 Location: Lake Villa, IL Status: Offline Points: 1797 |
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Both
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gun-driver
Grand Poobah Joined: July-18-2008 Location: Pittsburgh, Pa Status: Offline Points: 4127 |
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Have you adjusted your idle mixture screws at all???
https://www.youtube.com/watch?v=UPGLUsW5ZeE |
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