94 Ski Nautique Engine hesitation |
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CRPilot
Newbie Joined: March-07-2018 Location: Wisconsin Status: Offline Points: 14 |
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Posted: March-07-2018 at 12:59pm |
I'm looking for some help from the local experts. I've been chasing an engine hesitation for more than a season now and I've given up with the local dealers who "can't duplicate" the issue.
94 Ski Nautique PCM 351 Carburated with about 450 hours. The engine starts and idles good but can be a little cold blooded typical to carb'd engines. Once warm, but not completely head soaked, the engine will have a very distinct cut out when pulling a slalom skier up. More throttle = more cutout. After a second to two it catches and pulls up to and maintains cruising speed. Hard acceleration from 25-36 will trigger the cutout as well. A slow, low load acceleration will not cut out. It feels like someone pulls the tether for a second (checked that though ans its tight). After skiing for a bit the cutout gets worse as the engine completely heat soaks. At its worse I can't even pull skiiers up. At that point it feels like its missing on a cylinder or two. The carb's been rebuilt (by me) which had no impact on the issue what-so-ever. I wouldn't rule out carburation thought as it feels like a fueling issue to me. I've read a ton and there seems to be a list of potential issues but I honestly don't have the right tools or in some cased the mechanical expertise to diagnose the problem if I'm staring right at it. -Fuel pump - original -Fuel filter (replaced last year) -Fuel tank check valve?? (not sure what that is) -Accelerator pumps? -Probably many other possibilities... That's where I need someone that is good at trouble shooting. I'm located just west of Milw Wi. Does anyone have a recommendation for a person/mechanic that I can take this too? Or anyone close by and willing to meet me on a local lake and trouble shoot (when the ice goes out)? I don't want to loose another summer to frustration. Looking forward to getting this solved. Jim |
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63 Skier
Grand Poobah Joined: October-06-2006 Location: Concord, NH Status: Offline Points: 4269 |
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Here's my suggestions:
Check the anti-siphon valve at the fuel tank - not at all hard to do Check/replace the distributor cap and rotor, points if it has them. In general check ignition system from start to finish. Check the advance mechanism on the distributor - might not be operating smoothly. Check the fuel pressure delivered to the carb - need to put a gauge in-line. |
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'63 American Skier - '98 Sport Nautique
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63 Skier
Grand Poobah Joined: October-06-2006 Location: Concord, NH Status: Offline Points: 4269 |
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I'm not from around there, lots of people in your area. But, when you say you don't have the expertise, I'd be very surprised if someone who successfully rebuilt a carb can't do all of the above troubleshooting themselves. Nothing of course wrong with getting some help though!
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'63 American Skier - '98 Sport Nautique
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11050 |
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Sounds to me like it's an accelerator pump issue.
You must have replaced the accelerator pump diaphragm and maybe checked the adjustment when you rebuilt the carburetor The easiest thing would be to Google " Holley Accelerator pump adjustment" and make sure it's good and make sure you get a good squirt of gas out the nozzles when you move the throttle. |
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CRPilot
Newbie Joined: March-07-2018 Location: Wisconsin Status: Offline Points: 14 |
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Thanks for the vote of confidence on my abilities! I've raced motorcyles and rebuilt my own 2-stroke and 4-stroke motorcycle engines for 20+ years so I have the basic skills to attack some of these issues. What I lack in the specific knowledge of how the 351 fuel and ignition systems work. Not the same as a single cylinder thumper...
Forgot to mention this is the Proboss HO so it has the protec ignition. No points to check and to my knowledge no wear parts to replace. Not sure if there are other validation checks for it. Yes, I reset the accelerator pump squirt per the spec'd gap. Don't recall what the spec was but it was checked and there is a solid squirt of fuel when moving the throttle open. My boat is currently in storage but I'm taking notes of what to check when I can get to the boat: -Recheck accelerator pump adjustment -Anti-Siphon valve (hoping there is a "how-to" on line somewhere) -Fuel pressure - What pressure should it be and are there any in-line gauge kits that would be recommended? It'll be 3-4 weeks before I can get to the boat to start looking at this but if anyone is looking for a fun spring project I have one.... |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Well there you go then -bad protec. Works good cold then as soon as it gets hot ....
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11050 |
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It took 14 minutes for somebody to blame it on the Pro Tec system.
Slow day on CCF For CRPilot google 'Correctcraftfan Pro Tec and do some reading.. You've got a few weeks to get thru it all Whether it's the problem or not, it'll scare you |
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desertskier
Platinum Member Joined: December-19-2006 Location: Az Status: Offline Points: 1115 |
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Probably, or it could be IR voltage drop in dash wiring reducing the input voltage at the module. Measure the voltage at the 12.5A breaker on the back of the engine. It should be close to battery voltage. Also, it could be intermittently going into limp mode. Disconnect the oil pressure and engine temp switches on the engine and run it. |
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CRPilot
Newbie Joined: March-07-2018 Location: Wisconsin Status: Offline Points: 14 |
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I'll read more about the Protec as the thought has certainly crossed my mind. Right or wrong, the reasons I haven't concluded its it protec:
1. The issue exists when stone cold, right off the trailer. But the issue does get worse as everything heats up. 2. The dealer "tested" the protec ignition after an hours worth of run time on the boat (fully up to temp) and didn't detect any issues with the protec (and to be fair found no issue at all. ...) |
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desertskier
Platinum Member Joined: December-19-2006 Location: Az Status: Offline Points: 1115 |
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Here is an old thread I started after having a problem similar to what you are experiencing.
Wiring problems and some interesting discussions I am not saying that it isn't a fuel problem or a bad coil pack but if it is protec related there are a few things you can check that won't cost you anything and may fix it. Here are a couple of good threads: DUI Swap Re-wiring dash |
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throttle out
Senior Member Joined: May-11-2015 Location: Chelsea, MI Status: Offline Points: 153 |
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Did this issue come on like a switch or was it a gradual progression?
When not towing a skier if you ease into the throttle just right will the motor eventually allow full throttle at some point? From what I've read it sure sounds like fueling, when you rebuilt the carb did you use a "Holley" marine rebuild kit? If so that kit would've likely came with two power valves so I will assume you replaced your old one with one of the new ones. If you know four stroke motocross bikes than you well know the awesome Keihin FCR-MX carburetor. That carbs accelerator pump tuning is absolutely critical, so try to treat your boats Holley in the same fashion. Just my 2 pennies! Good luck man! |
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1989 Ski Nautique 2001 351 PCM w/ 1-1.23
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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There is a saying, 90% of carburetor problems are electrical. Please keep us in the loop when you find the cause
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11050 |
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And about an equal number of ignition problems are carburetor/fuel |
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desertskier
Platinum Member Joined: December-19-2006 Location: Az Status: Offline Points: 1115 |
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Another member "TucsonMike" has a '94 and experienced what he thought was a protec failure.
His post: "Almost forgot - My symptom is the engine had a rough idle that would sometimes be 900 rpm, then almost die. It was intermittent misfire from the Pro-tec - the port bank of cylinders had fouled plugs, while the starboard bank looked perfect. The PCM guys said that symptom is the coils going bad. So - I have the original ECM with the coils attached and the PCM 'distributor'. Maybe the module is OK... Pay shipping and they are yours... " The DUI swap didn't fix it. He found that one of the gaskets in his carb was the wrong one. Swapped out the gasket and fixed his problem. Boat ran fine after that but later that year he found water in the oil and had to install new risers and manifolds. The good news is that I now carry a spare set of protec parts in my boat. |
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CRPilot
Newbie Joined: March-07-2018 Location: Wisconsin Status: Offline Points: 14 |
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Lots of great info guys. Thanks. I have a growing list of stuff to check.
Answer a few of the questions: 1. The engine only hesitates for a few seconds or less. Once it pulls through it has never had an issue revving right to top speed (~47 ish). 2. It has never gone into limp mode. 3. Yes, it was a Holley Marine rebuild kit. but it only came with one power valve. I don't recall if it was the same as what I pulled out but I do know that there was a ton of online chat about which one to use. If it was changed by one size, would that trigger an issue? The hesitate was there before the rebuilt and was actually the reason I rebuilt it. I didn't notice any performance change after the rebuild. I never had to deal with the FCR. I ran two strokes (38PWK) until the 4 strokes were EFI. EFI just makes life easy vs jetting for weather and altitude. |
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desertskier
Platinum Member Joined: December-19-2006 Location: Az Status: Offline Points: 1115 |
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If the module is malfunctioning because of low input voltage it may or may not be going into limp mode but the dash light probably would not be a good indicator. When mine was failing it would cutout during acceleration and it was worse when trying to pull a skier.
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KRoundy
Platinum Member Joined: August-23-2010 Location: Lake Stevens Status: Offline Points: 1702 |
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Quick question - did you replace the gasket when you installed the rebuilt carb?
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Previous: 1993 Electric Blue/Charcoal Ski Nautique
Current: 2016 Ski Nautique 200 Open Bow |
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CRPilot
Newbie Joined: March-07-2018 Location: Wisconsin Status: Offline Points: 14 |
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I plan to check the dash and ignition wiring as soon as I get to the boat. I have some dielectric grease I can use to combat corrosion if any exists.
Which gasket are you asking about? The float bowl, metering block, and primary to secondary tube o-rings were all replaced. Based on all the comments and suggested reading so far far im thinking it’s the anti-siphon or fuel pickup in the tank. While suttle, the problem seemed to we worse with lower fuel tank levels. A full tank didn’t eliminate it but seemed to minimize a bit. I’m kinda looking forward to getting my hands in the boat and checking these things. |
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Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4947 |
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I assume Kevin is talking about the carb > manifold gasket. Or potentially, the carb to spacer gasket. A bad (or flimsy) gasket there can cause a vacuum leak, which could give similar symptoms to what you are experiencing. http://www.skidim.com/GASKET-CARBURETOR-SPACER/productinfo/RM0054B/ |
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CRPilot
Newbie Joined: March-07-2018 Location: Wisconsin Status: Offline Points: 14 |
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Got it. No I did not pull the carb off the spacer or manifold so those are original. I find it hard to believe that seal would start to fail on a low vacuum application like this...but stranger things have happened. Is there a test to see of the gaskets are bad or is it just remove and replace? "If its not broken, don't fix it.."
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SNobsessed
Grand Poobah Joined: October-21-2007 Location: IA Status: Offline Points: 7102 |
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One test for vacuum leak is to spray carb cleaner on the suspect area, with engine running. If there is a leak the engine will sound different suddenly.
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“Beer is proof that God loves us and wants us to be happy.”
Ben Franklin |
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Dreaming
Platinum Member Joined: May-21-2010 Location: Tacoma, WA Status: Offline Points: 1870 |
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CRP - I have a 94 and was experiencing a similar issue that was carb related. You say that you rebuilt the carb, but never pulled it off of the engine? I think a full carb rebuild would be in order, as it sounds much like you have a secondary issue to me. KenO could be on the right track with accelerator pump though, since in either scenario you describe, you would be using it. A carb rebuild would require you to replace gaskets, but more importantly to clean all of the passage ways, replace the needle and seats, adjust the floats etc. Vacuum leaks can develop over time if your gasket (spacer to manifold or carb to spacer, there are usually 2 in a 94HO) are bad, or rattling, or whatever. The carb will come off with the 4 7/16ths nuts on the base, and you can disconnect the throttle arm and choke electrical with the quick disconnects. the only "tricky" part to removing is that you need to get a flare nut wrench on the fuel line, which really isn't that much of a big deal at all. Lots of Online help if you get stuck rebuilding a Holley...
Good luck! |
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Jonny Quest
Grand Poobah Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 2957 |
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+1 on what KENO said. Sure sounds like an accelerator pump issue. As recommended, I would take the carb off and do a complete re-build. Not terribly difficult and lots of material on the internet on the Holley 4160. Summit Racing also has good Holley carb videos.
I know that the ProTech system takes a lot of flak, but its justified in many cases. My 1994 had the "double trouble" of ProTec and the throttle body EFI. A ProTech system that is going bad can exhibit a wide variety of symptoms. And like many electronic components, the failure may not always be consistent nor predictable. It's a fairly simple change-out to replace the ProTech to a high performance distributor -- such as a DUI or Davis Unified Ignition HEI system. Lots of info here on that. 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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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11050 |
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I'm not sure why you think the anti siphon valve or the pickup tube would only affect you coming off idle and not when the boat is running at a steady high speed. Plugging/restriction from those issues will starve the engine for fuel as the speed and load get higher and it sounds like once you get it past the hesitation, then things are OK. Hook a temporary tank to the fuel pump inlet and see how it drives on the water. If it runs the same, you know it's not because of problems with anything before the fuel pump like the pickup tube or the anti siphon valve. Seeing the recent posts, it's hard to tell if you "rebuilt" the carburetor while it was still on the engine based on the gasket comments. You say you don't have much Holley experience,you need to get yourself one of the many Holley books that are out there for around 25 bucks and do some reading. It's money well spent. Here's a link to a thread talking about spacer gaskets and a picture of the spacer. Your's may look the same or a little different, but you can see why they can leak because there isn't a lot of sealing area, they get old and brittle and you have problems. link Once you figure you've ruled out fuel issues, then it's on to the Pro Tec possibilities |
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KRoundy
Platinum Member Joined: August-23-2010 Location: Lake Stevens Status: Offline Points: 1702 |
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You rebuilt the carb without removing it from the engine? I think we are all suspicious of this method or rebuilding a carburetor. A full removal and full rebuild would be a good first step. If you do this and it still hesitates, then we can move on to the fuel pump or the Pro-Tec. The write-up on how to install a Pro-Tec is linked in the FAQ.
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Previous: 1993 Electric Blue/Charcoal Ski Nautique
Current: 2016 Ski Nautique 200 Open Bow |
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KRoundy
Platinum Member Joined: August-23-2010 Location: Lake Stevens Status: Offline Points: 1702 |
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OK - I will stop being lazy.
Carb Rebuild Repacing ProTec ignition with DUI Note - you need to have the "Photobucket fix" for this to work right. |
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Previous: 1993 Electric Blue/Charcoal Ski Nautique
Current: 2016 Ski Nautique 200 Open Bow |
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CRPilot
Newbie Joined: March-07-2018 Location: Wisconsin Status: Offline Points: 14 |
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Been away for a few days but still lots of good info.
First off, rebuilding the carb: You can pull both the primary and secondary bowls off the main unit, giving access to the metering plates and associated gaskets. Metering plates were cleaned/blown out, needle and seats replaced, power jet replaced, and jets cleaned/ blown out. The passages into the main body were cleaned with carb cleaner and blown out. Then reassembled with new everything. The carb body does not need to be removed to do that work. I did not remove the nozzel or j-tubs as there is noting to service. They appear to be flowing fuel just fine. For those that have done this rebuild, please tell me what part of the rebuild cannot be completed with the main body attached (other than the obvious manifold gaskets)? I'm not arguing, but I don't understand what part of the rebuild was missed by not removing the body. (again, excluding the manifold gasket). With that said, the manifold gaskets could be an issue and I need to remove that from the equation by replacing it. No argument. What is the consensus on the power jet size? I've read a ton and there doesn't seem to be agreement on one size. Regarding the siphon or pick up tube: My thoughts were upon acceleration the engines immediate demand for fuel from the tank (pre fuel pump) would be at its highest for a second or two (highest vacuum on the fuel line). Once the fuel flow is stable (and not accelerating) any pick up issues might not be as noticeable. Lightly suck on a straw with a hole and you might not notice the hole. Take a strong pull and you will suck air into the straw.....Might be flawed thinking but it made sense in my head. I need to try hooking up an auxiliary tank and see if that helps. I can check these basics when I get to the boat but after that, I may be at the limit of my skill set. I can R&R parts but I still can't compare my abilities to those people that really know these boats and systems. There value is recognizing the minor issues that affect performance in a big way. Thanks again. |
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Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4947 |
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When the engine is accelerating, the accelerator pump is shooting a squirt of fuel that was previously in the carb fuel bowl, so, it's not necessarily a greater pull from the fuel tank at that point. Sustained high speed would give you your greatest flow from the tank perspective.
Actually, it sounds like you covered the most important aspects of the rebuild with the carb body still attached. Maybe not the easiest way to do it, but I guess there's nothing inherently wrong with that approach. I'd give your accelerator pump lever adjustment the hairy eyeball one more time. Any play there can give you a bog, that thing needs to be squirting the instant the throttle plates open. |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11050 |
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Well the most obvious reason is that it's hard to dunk the carburetor in cleaner unless you have a really big tank
A few other reasons though are You can't check the tightness of the screws that hold the throttle body to the main body. There are 8 screws and there's a gasket between the main body and throttle body. It would be one of those leftover parts in your kit. I've seen plenty of screws that were not very tight at all allowing the gasket to leak. some. You find those 8 screws when you turn the carburetor over. As mentioned before the gaskets on either side of the spacer should be checked and there's only one way to do that. Did you take the secondary metering plate off so the secondary idle passages and main passages could be cleaned Some gaskets, especially on the secondary metering plate are a royal PIA to get apart and scrape when the carb is on the bench and harder than that when it's still on the engine. You get a lot better look at the idle transfer slots and curb idle discharge ports when the carb is upside down in your hands.and you can blow air backwards through them There are other things too, but you get the idea As far as power valves go, if you put back in the same size you took out, you're not screwing with the Holley calibration and that's generally a good thing. If you don't know what it had you can find the Holley list # on the front of the air horn and post it and somebody will tell you what the original power valve was. By 1994 there's a good chance it was a 2.5 but it's worth verifying. |
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throttle out
Senior Member Joined: May-11-2015 Location: Chelsea, MI Status: Offline Points: 153 |
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The size of the power valve will not make or break performance but more improve or reduce if that makes sense. I asked you about it to be sure you had in fact replaced it.
To narrow this down for you; - given your motor will take full throttle and run well so long as throttle is applied gracefully, I feel as though your fuel delivery to the carburetor is likely sufficient. - The previous statement also tells me your ignition system is likely "good enough" at least This to me is without a doubt an accelerator pump issue that existed previous to the rebuild and has yet to be addressed. I would not go around your boat inspecting anything else until I was certain the accelerator pump circuit on your carb is functioning 100% and is tuned properly. You also indicated it starting hard. This again is an indication of a weak accel pump circuit as it is what shoots fuel down the throat of your motor when you give it a couple pumps before turning the key on the motor when cold. |
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1989 Ski Nautique 2001 351 PCM w/ 1-1.23
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