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Engine hesitation

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Gumbrell View Drop Down
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    Posted: February-22-2017 at 5:14pm
Hi
I have owned a 1992 Ski Nautique for about 22 years with no problems whatsoever
It has a pcm 5.7 engine with Pro Tec ignition system
Recently I have noticed a very slight hesitation on pulling away when the engine is warm, this doesn't affect performance either with or without a skier. The strange thing is that this doesn't occur when the engine is cold and the auto choke is activated
I initially thought the problem was electrical so fitted new plugs and high quality ht leads, but this made no difference
I'm now wondering if it could be a fuelling issue
Has anybody experienced this, any advice or suggestions would be most welcome
Thanks,
Michael
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Post Options Post Options   Thanks (0) Thanks(0)   Quote quinner Quote  Post ReplyReply Direct Link To This Post Posted: February-22-2017 at 5:24pm
Your ProTec is on it's way out, Ski-Dim has a retrofit replacement kit or using a DUI distributor is another option.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gumbrell Quote  Post ReplyReply Direct Link To This Post Posted: February-22-2017 at 5:27pm
Hi
Thanks for the prompt reply, which system would you go with, what's the diffence
Michael
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Orlando76 Quote  Post ReplyReply Direct Link To This Post Posted: February-22-2017 at 6:38pm
Well, if you can screw in a light bulb then you can convert to a DUI. There's a few threads on it, maybe a FAQ page.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote velde99 Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 1:14am
Doing the DUI to mine.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote velde99 Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 1:15am

http://www.correctcraftfan.com/forum/forum_posts.asp?TID=34338

May have to paste the link.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JD ski Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 1:48am
If this is a well known issue then listen to the above advice. But with the mention of the chock position makes me think of a gummed up jet. Even though the motor is not fuel injected I would run a bottle of fuel injector cleaner through the tank. It is inexpensive, won't hurt anything, and may solve your problem. If not you have narrowed your search.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JPASS Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 8:36am
Fixed the link

More good info here


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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 9:02am
Michael,
As mentioned, the Pro Tech systems are prone to fail so a conversion is a good idea even if that's not the problem. You mention a fuel issue as being a potential problem. Have you checked to see if the accelerator pump is working squirting a shot of fuel when you accelerate?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote quinner Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 10:05am
Hold the phone ........
did Pete just suggest throwing parts at the problem, lmao!! Welcome to the hobbyist backyard hack club!!
ok, he is kind of right, protech biting the bullet is not a matter of if but when, mine tanked at 10yrs old so at 24 you are definitely on borrowed time.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GottaSki Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 11:22am
Protec is suspect for sure, but not conclusively. what is the carburation on the 5.7?

There is a possibility the idle fuel orifice is clogged on the primary metering block.
That would induce a hesitation/stutter off idle that would not present when choked.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rolleronariver Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 1:55pm
My 92 sport was doing this last summer. I rebuilt the holly carb and put a new fuel pump on and now it runs great! I think my accelerator pump went bad but I figured I'd go ahead and change it all while I was working on it. I hope this helps.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote backfoot100 Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 2:28pm
Originally posted by GottaSki GottaSki wrote:

Protec is suspect for sure, but not conclusively. what is the carburation on the 5.7?

There is a possibility the idle fuel orifice is clogged on the primary metering block.
That would induce a hesitation/stutter off idle that would not present when choked.


Agreed.
Everyone wants to blast the Protec every time. Granted the inevitable option of replacing it is the only one available as many have done here. The known issues of it are also well documented. That said, there are still way more boats out there running the original Protec than those that have been replaced. To just assume that is the problem at the slightest hiccup is completely a back yard hack solution. Now that even includes Pete for Christ's sake.
If a 20 +year old boat has a carb that has probably never been touched it would probably be a good idea to do a rebuild on that carb before anything else. Especially considering that said boat has been given a good tune first which didn't fix the issue.


I have a BIL that has a 92 Pro Boss with a Protec and 1500hrs. that runs perfectly. He's acutely aware of the potential Protec replacement He's had some minor issues with it and each time he found loose or corroded wiring under the dash that fixed any weird issues that he's run into. And this is from a very mechanically challenged guy.
When people run down to the lake to see what's making that noise, you've succeeded.



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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gumbrell Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 3:37pm
Hi everyone
I've only just joined the forum and can't believe the number of really helpful responses that I've received already
As regards the carb I ran a cleaner through with the fuel and then used an aerosol cleaner direct into the carb, all this with no noticeable difference
I think the idea of having the carb overhauled is a positive one, however here in the U.K. We have very few people who have a good working knowledge of our boats. I phoned one boat mechanic who has done some work on other boars on our lake and his response without even seeing the boat was Protec, they are rubbish, ill convert it to a distributor with points and it will cost £1300.00
I would say converting back to points would definitely be a retrograde step so didn't use him
As I say I think I will go with a carb overhaul and a DUI upgrade. Thanks again, Michael
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Post Options Post Options   Thanks (0) Thanks(0)   Quote desertskier Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 4:22pm
I also have a '92 with many hours on it and the original Protec. This sounds more like a carb problem. When mine started giving me similar problems I rebuilt the carb which worked for a while then it started acting up again so I bought a new Holley 4160 and it has been running well since.   I figured after 20+ years it deserved a new carb. In regards to wiring problems and the Protec it may be a good idea to check the operating voltage going into the Protec. Turn the key on and measure the voltage at the 12.5 amp breaker on the back of the engine. It should be close to 12V. If it is low then you probably have a wiring problem that may or may not be causing you problems but should probably be addressed. Our boats are notorious for having bad dash wiring.   Another suggestion would be to remove the Protec connector at the module and clean it with rubbing alcohol.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rolleronariver Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 4:26pm
As far as finding people to rebuild your current carb, the holly carbs are very similar to a car engine holly carb. I would suggest removing it yourself, buying the correct rebuild kit, and taking it all to any mechanic shop that works on holly's and ask them to rebuild it with the kit you bought if you don't feel comfortable doing it yourself. There's some great videos online showing you how to rebuild one too.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 4:29pm
Originally posted by Gumbrell Gumbrell wrote:

ill convert it to a distributor with points and it will cost £1300.00
I would say converting back to points would definitely be a retrograde step so didn't use him
As I say I think I will go with a carb overhaul and a DUI upgrade. Thanks again, Michael

Michael,
Why do you feel points would be a "retrograde"? That mechanic evidently doesn't feel that way! There are plenty of engines running points and have for years. I feel some don't like them because they simply do not know how to set dwell!!


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Post Options Post Options   Thanks (0) Thanks(0)   Quote GottaSki Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 4:39pm
Just to avoid frustration...

IF at idle, the secondary return rod is found sloppy, and one can rotate the secondary throttle plate by hand about 3-4 mm before hitting the stop, Do not bend the rod to remedy.

It is evidence one or both the idle fuel orifices are clogged, and someone increased the idle stop to get the engine to idle once more.

The two idle fuel orifice are buried deep in the metering block, out of view, of small diameter, and clog very easily. Most people who say their engine runs 'fine' have a clogged idle circuit.. It should run effin fantastic.

The basic carb rebuild will not remedy unless the rebuilder is privy to the failure mode, and uses compressed air in the right manner to verify the flow is now unimpeded.
Cleaning the orifice of debris, is a blind science.

Naturally, fuel filtration is of utmost importance.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 4:47pm
Originally posted by GottaSki GottaSki wrote:



IF at idle, the secondary return rod is found sloppy, and one can rotate the secondary throttle plate by hand about 3-4 mm before hitting the stop, Do not bend the rod to remedy.

It is evidence one or both the idle fuel orifices are clogged, and someone increased the idle stop to get the engine to idle once more.

Tom, can you explain in more detail? I've definitely encountered carbs whose secondaries hang open a little after a hard run, which was attributed to a sloppy return rod. It seems the rod is used to force the secondaries all the way back to the stop. Whether or not that stop is set correctly (compensating for clogged idle circuits?) seems like another issue. If they're cracked further open to raise the idle, shouldn't the rod be overly tight rather than loose (in the closed position)?

Or am I out in left field here?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote desertskier Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 4:51pm
Just an FYI - My boat originally came with a Holley 4010 Fishbowl. He may have one also.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JPASS Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 9:15pm
Originally posted by desertskier desertskier wrote:

Just an FYI - My boat originally came with a Holley 4010 Fishbowl. He may have one also.


Our '92 had the 4010 as well.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 9:30pm
Originally posted by TRBenj TRBenj wrote:

Originally posted by GottaSki GottaSki wrote:



IF at idle, the secondary return rod is found sloppy, and one can rotate the secondary throttle plate by hand about 3-4 mm before hitting the stop, Do not bend the rod to remedy.

It is evidence one or both the idle fuel orifices are clogged, and someone increased the idle stop to get the engine to idle once more.

Tom, can you explain in more detail? I've definitely encountered carbs whose secondaries hang open a little after a hard run, which was attributed to a sloppy return rod. It seems the rod is used to force the secondaries all the way back to the stop. Whether or not that stop is set correctly (compensating for clogged idle circuits?) seems like another issue. If they're cracked further open to raise the idle, shouldn't the rod be overly tight rather than loose (in the closed position)?

Or am I out in left field here?


Here are a couple of pictures of a 4160 with the linkage rod shown.

First one is at idle

Second one with the throttle partially open

So, the farther open the primaries are, the more slop there is.

To me the purpose of the rod is to make sure the secondaries are never farther open than the primaries.whether you're increasing or decreasing throttle position

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jonny Quest Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 11:00pm
I agree with previous posts. The Pro-Tech system has a high likelihood of failure and the failure can manifest itself in various ways: Failure to start, missing at various RPMs, etc. The coil packs typically go bad and then you are running on less than all cylinders.

The other recommendation would be to look at the accelerator pump. Not unusual for an older pump like that to fail. The diaphragm can leak and you won't get a good strong shot of gas when you hit the throttle. You could do a carb rebuild/refresh or simply upgrade to the QuickFuel M-600! Lot's of good reviews on that carb.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: February-23-2017 at 11:19pm
Tom, I thought you were talking about misadjusted secondary butterflies... it dawned on me you were talking about the primaries. I'm following now.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 93xs2003@gmail.com Quote  Post ReplyReply Direct Link To This Post Posted: February-24-2017 at 9:49am
I was having trouble achieving a good idle.   No vacuum leak. Set up with proper transition slot exposure, both sides. Carb wanted idle mix screws turned out to the extent that they were no longer modulating mixture,   It ran, but needed relatively high idle RPM (timing adv) to avoid damper plate rattle.   This was on a fresh rebuild.

At the end of the summer, I dug into it. Inserting a toothpick in one of the secondary air idle bleeds would cause a significant increase in idle rpm, suggesting the at least one carb bore was lean at idle.   Idle screws turned out too far, and one bank is still lean???? On disassembly, probing with a wire-drill set I found the secondary metering plate had one idle fuel restriction orifices drilled undersized.   I missed this on the earlier rebuild. Parts were clean and clear, but I hadn't thought to verify orifice diameters.

I'll have to wait until spring to get it out on the water, but idle in the driveway has improved.   Idle mix screws are now in a range where they can modulate flow.

I expect having a lean carb bore was causing inconsistent output and limiting the minimum RPM above damper plate rattle.

This one was a clear QC issue from holley, and it had been running this way for 24 years.   OK, but not great.

The point of all this is a toothpick might help you diagnose the clogged idle circuit that Tom mentioned.   I would expect that covering a idle air bleed to cause an unclogged idle circuit to go fat.
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