problem solving engine trouble |
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Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4947 |
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I started poking around a little bit. I guess there are different sizes and vacuum ratings for pcv valves, which makes sense. Something I honestly gave hardly any thought to. You might have one with too small a diameter.
You're right that's it's a when-in-doubt-replace-it sort of part. |
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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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any idea how to figure out which PCV valve/grommet I need for my engine? I've been digging around all morning and can't find anything that says exactly what I need. I found this pcv at skidim... http://www.skidim.com/VALVE-PCV-90-DEGREE/productinfo/R035015/ ...but haven't been able to find an exact replacement grommet. I would love to find an automotive equivalent that I can pick up in town so I can check it out today. |
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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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Any luck? I'd imagine the grommet would be kind of standard for all 351s?
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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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A new PCV valve and hose arrived today. The grommet appeared to be fine so I'm leaving it in. I'll get these in tomorrow and give it a try. I'll report back once I know something.
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Luke Pearson
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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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okay, here is where I'm at now:
PCV Valve didn't fix the problem although the old one was definitely worn out and not functioning properly. Timing is now set correctly (according to manual). I've been at the lake with the boat twice this week to think through possible scenarios. Here is what's happening: -The boat is now idling fine. -The boat starts quickly and accelerates quickly. It takes fuel fine. I can throw the throttle down and it will take fuel and accelerate without a hitch. -It runs fine below 2000 RPM and above 3000 RPM. -When I bring the boat to approx. 2500 RPM and let it cruise at that speed, it takes about a minute before it starts to stumble. -The stumble sounds like its too lean or too rich ( I can't tell). -The stumble last for about 2 seconds before it catches back up and resumes speed. -3 seconds later the stumble happens again. -This stumble pattern just continues as long as you keep the boat under load between 2000-3000 rpm. (Its the worst around 2500). Every 3 seconds like clockwork. -If you accelerate really quickly and run the boat hard for a few seconds and then bring it back down to 2500 rpm, then it takes about a minute before the stumble starts again. Any other ideas based on that? Could float levels cause these symptoms? I have new gaskets from Skidimi and new jets for the carb (a size up and a size down). I plan on trying the jets first. If that doesn't work then I'll take the carb off, clean the surfaces, and use the new gaskets to hopefully fix any vacuum leaks (although I haven't been able to find any). Thanks for following this thread and helping me troubleshoot. |
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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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You could watch the secondaries' linkage when it is acting up. Maybe there is something wrong with the secondaries vacuum diaphram, like a pinhole.
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“Beer is proof that God loves us and wants us to be happy.”
Ben Franklin |
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Chris74
Newbie Joined: July-25-2016 Location: L8G 2A8 Status: Offline Points: 33 |
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Sounds like a lot of the same problems I'm having.the information I found on vacume said it suhould read around 16
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Chris74
Newbie Joined: July-25-2016 Location: L8G 2A8 Status: Offline Points: 33 |
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What did your manual tell you to set timing to ?
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MrMcD
Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3735 |
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Have you verified the timing is advancing smoothly from idle all the way up and not jumping and sticking as you increase RPM.
Easy check, install a timing light and watch the timing marks as you rev the engine. Should be identical each and every time and very smooth as the timing moves from your idle setting to max centrifugal advance. Common problem in boats is rust on the distributor advance weights making them sticky. I have seen this problem twice in friends boats. |
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MrMcD
Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3735 |
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I see you set the timing and I guess you did this at idle which is normal.
Engine performance is very much controlled by the Mechanical advance in your distributor. It normally functions perfectly and is invisible. When they act up you need to verify what they are doing to fix them or verify it is working perfect and move on to other potential problems. The simple check would be to hook up the timing light to your number one spark plug. If you question what plug is number one, look down on the front of your engine above your fan belts. As you look down notice that one cylinder head is actually about 1 inch forward of the other cylinder head. The forward head and the front cylinder is where your number 1 plug will be located, Chevy, Ford Chrysler all the same., With the engine running and timing light working have a partner rev the engine up slowly from idle 650 RPM to 4,000 RPM watch the timing mark on your harmonic balancer move. It should move from the factory setting of 5 degrees or so at idle all the way up to 35 degrees by 3,000 RPM. If it is sticky, jumpy or does not move this is a major issue and needs fixed. Fix is simple, take the cap off the distributor remove the points and condenser and get down to your advance weights under the points. Make sure they are clean, no rust. The springs are still attached. Turn the shaft gently and watch the springs move and the weights swing. Make sure the weights are clean and smooth. If you take them out a quick smoothing with 600 grit sand paper will make them work well again. I always coat them with a very thin film of marine grease. I understand many say to keep them bone dry. I use the thin coating, just a film, to help avoid future rust. I know the coating can attract dirt and dust. Choose your poison, dirt or rust both can mess it up. Timing should advance as RPM goes up. If you are 5 at idle it might be 15 at 1,500 RPM and 20 at 2,000-2,500 and max at 35 + or - 1 at 3,000-3,500. Keep checking all the way to 4,000 so you are positive where it stops advancing. As was mentioned many posts back on this thread timing could cause your issues if it is not advancing correctly as your RPM go up. |
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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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10 BTDC |
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Luke Pearson
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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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Good idea. We thought the same thing and watched these good. No sign of leakage from secondaries.. |
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Luke Pearson
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Chris74
Newbie Joined: July-25-2016 Location: L8G 2A8 Status: Offline Points: 33 |
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I have checked for advance it is good and smooth.get up just over 30 at 3500 rpm.My timing marks only go up to 30.The distributer seems to be fine.i honestly think my whole problem has been timing.will verify this week end though .The confusing thing is wether it should actually be 5 or 10 degrees..From what I can tell now I believe my motor be a WRD motor actually refers to RD setting which say the timing should be at 10 degrees not 5 which I have been setting it to for years.
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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 double check this today. Pretty sure timing is advancing correctly though. I'm not getting any pings or backfires. Boat accelerates fine and runs great at high RPMs. Also not sure why it would run fine for a minute before the stumbling starts if it was a timing issue. It is literally like clock work. It'll run perfect at 2500 RPM for 1 minute and then start stumbling every 3 seconds until you accelerate. When you bring it back down to 2500 rpm it will take another minute to start stumbling. and maybe stumbling is the wrong word. It sounds like a bog; as if it's getting too much fuel or starving for fuel. |
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Luke Pearson
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MrMcD
Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3735 |
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Run the timing your engine calls for, it is not the same in all engines. That is why some say 5 and some say 10 degrees. Run what your engine calls for as a base.
If your timing advances smoothly every time and does go up over 30 as you state it, you ruled out timing as a possible cause. Check it off. If it is sticking at any point it can cause big headaches and boat distributors do rust and eventually stick. or the springs rust out and fail making your advance curve bad. For your engine to perform timing has to advance smooth and linear, each time the RPM changes. My carb knowledge is weak so I will let the experienced help you on that. I would think if you can run it wide open for a minute and not starve for fuel you don't have a supply issue or a float issue. A leaking diaphragm on the secondarys would leave them closed at all times and cost you power but not make it run erratically. From what you describe it sounds like the secondarys in your 4 barrel are working fine and the primary system is where your issue is. When you water test it have help to drive for you. With the engine cover up manually open the secondarys and see if your problem happens at 2,500 running on the secondary with the primary still set at idle. Might give you a clue where to focus. |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11061 |
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Hi LiftFilms
Having read thru all of this thread and all of last year's, I don't see any mention of what kind of distributor you have. Lots of talk about timing and advance mechanisms, nothing about points or electronic. I've seen both do some strange things.that are hard to explain. Will the boat run at say 3000 or 3500 rpm's for a minute or more with no issues? If I put on a brand new carb and that didn't resolve my issues I'd be looking elsewhere and I can't count how many times over the years I've been sure something was a fuel issue only to figure out it was ignition instead KenO |
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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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It is a prestolite sae-j1171 Once you get to 3500 rpm the problem goes away completely. at 3000 rpm it is there but almost unnoticeable. at 2500 it is the worst. below 1800 it is non-existent. |
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Luke Pearson
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11061 |
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The SAE j1171 just m eans it's a marine distributor. That was the SAE testing that qualified it as marine. But at least you know it's a marine Prestolite If it's points and you haven't touched them in a while, I'd do points, rotor, cap and condenser and a coil while I was at it. Just a stock replacement type coil Can't hurt that's for sure. Electronic might have it's own set of problems that would be a little harder. KenO. |
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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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Update:
I went out to the lake today and tried switching out the jets so I could mark another thing off the list. The carb came with 67 jets from the factory. I tried 65 jets and didn't notice much of a difference. I then tried the 69 jets and the boat ran noticeably worse. It idled worse, had less power, bogged, etc. I'll switch it back to factory size and mark the jets off the list. I didn't have anyone with me where I could check timing advance. I'll try that tomorrow or monday. |
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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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Listen to KENO. I'd continue to troubleshoot the ignition... Doesn't sound like carb. I've seen EI modules misbehave at specific rpm and act fine above/below.
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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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I'm moving to ignition now. My boat has standard ignition with points. I'll start checking each of KENO's suggestions off the list. thanks for the help.
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Luke Pearson
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11061 |
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If you want some part numbers, here goes. These are for the Prestolite clip down cap which is what came on the 76's. If you have the later screw down cap the cap and rotor are different These are all Standard Motor Products but could be cross referenced to another brand Points AL-5677P Condenser AL-118 Rotor AL-153 Cap AL-140 (cheap one) or AL-483 (expensive one, brass contacts instead of aluminum) Coil UF-2 Ballast resistor RU-4 (RU-23 or RU-37 will work too) Or you can go to discount Inboard Marine's website and get a 1301 tuneup kit (cap, rotor, points and condenser) and 1243 ballast resistor and 1223 coil. May or may not cure your problem, but you'll know your ignition system is right. KenO |
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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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My cap is the screw down version. So the cap and rotor are the only things that are different? Which brings up another point. What is the best way to tell what year model a nautique is? The papers for my boat show two different numbers. Previous owners didn't keep up the documents very well so there was a lot of confusion when I purchased it. I really want to know the source of the problem so my plan is to change components one at a time until the problem goes away. |
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Luke Pearson
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MrMcD
Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3735 |
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My 78 had a serial number in the back drivers side right below the rub rail and the year of build was in that number.
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11061 |
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If it's a screw down cap then you would use a 1302 kit from Discount Inboard Marine instead of the 1301.
I don't have any Standard brand numbers written down for the cap and rotor for the screwdown cap. |
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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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KENO,
Just getting back on this. I just double checked and my distributor has the electronic conversion. It has the screw down cap with a Mallory 6100M Distributor Module. What do you recommend doing on that? |
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Luke Pearson
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11061 |
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Hi Lift Films
Bet you were surprised when you popped the cap. I think about all you could do short of replacing the e spark unit would be to clean the rotor and cap contacts if there is any corrosion etc on them. That would be by scraping the stuff. off. You could clean the photo optic eye with some spray electrical contact cleaner. Don't use brake parts cleaner. We won't get into why I say that If I suggest getting a new e spark kit, it'll probably turn out to be wrong and not cure your issue, then again if you don't get one you won't know. Kinda a Catch 22 situation. Like TRBenj mentioned earlier the electronics can do strange things, but I'd start by making sure things are clean like I mentioned above One other thing, look at the Mallory instructions and make sure it's wired the way they tell you to. Much of this depends on what you're using for a coil. KenO |
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Lift Films
Newbie Joined: June-09-2015 Location: Raleigh, NC Status: Offline Points: 38 |
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Thanks KENO. Should the coil be the same as the one you mentioned earlier? UF-2?
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Luke Pearson
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fanofccfan
Platinum Member Joined: December-13-2009 Location: North Bend NE Status: Offline Points: 1774 |
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For what it is worth. I took a screen shot of KENO's above post with the part numbers. Took it to the parts store ordered them all and was up and running in no time!
Thanks KENO, |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11061 |
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The coil I've been using with an e spark is a Mallory 29219 mallory instructions The linked instructions talk about coils and ballast resistors right at the beginning, the 29219 is one of the 3 listed for use without a ballast resistor. I went that route and haven't had any problems The instructions can be confusing, these particular ones are for an e spark in a Mallory distributor but the wiring is the same for all the e spark kits. |
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