still getting a few backfires
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=4191
Printed Date: November-30-2024 at 10:37am
Topic: still getting a few backfires
Posted By: tommer12
Subject: still getting a few backfires
Date Posted: July-15-2006 at 9:46pm
I'm not sure where to turn with this:
1992 SNOB 351 ProTech
Rebuilt carb (shop did)
new plugs
new gas/water filter
new pv
new accelerator pump
I'm still getting a few backfires when I hit it. The carb has been completely tested and redone. I had a hunch that it could be the following.
I do have a stereo system that could be screwing up the ProTech... not sure if it could or not. I have two amps, yada yada... but I a feeling that the stereo is drawing too much and screwing up the protech timing which is causing the backfires. From understanding, the Protech system will auto adjust itself to keep the enigine timed where it should be. If the some sort of voltage drop was happening, could this be screwing with my protech?
My other thought it could be something simple. The boat did smell a little gassy... as it was dumping too much in the carb which may have cause the pops. Is there a good guide or instructions on how the screws should be set?
I can still seem to run it fine after I feather it up or slowly to plane and then wot is fine. Someone said to try some 91 octane instead of 87 and maybe it will go away... (yeah.. I know. things just don't go away by thmselves... but)
vaccum?
thanks fellas!
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Replies:
Posted By: Munday
Date Posted: July-16-2006 at 11:18pm
Check base timing bout all you can do to protec
Run compression test,Sounds like the same way my 92 ran with a lobe knocked down on cam shaft
did it have any odd lookin plugs when you changed them?
Good luck Munday
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Posted By: tommer12
Date Posted: July-16-2006 at 11:51pm
with a lobe knocked down the cam shaft? Not sure what that is.
I can do a compression test and see.. but what will that tell me? I can pull stumps out and run at about 40 mph.......
I ran 91 in it today and it seemed better, but I did get one backfire at start up out of the hole. It's very odd. I would think that the ProTech would either work or not work.. no run at 50 percent....
I can pull the plugs and check them out.
thanks much!
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Posted By: GottaSki
Date Posted: July-17-2006 at 6:45am
Base timing retarded and/or sloppy accel pump.
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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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Posted By: David F
Date Posted: July-18-2006 at 10:25am
Hey Munday:
I have never heard of just one lobe failing on a camshaft. Usually they all go and during initial 20 minute break-in. Also, did the bearings in your motor survive all the metal from the failed lobe? or was it a gradual thing?
Last month or so, I help my father-in-law put a rebuilt chevy engine in his truck. The truck was old, so went with a long block from a local machine shop/engine exchanger. Got it all installed, start up great and 15 minutes later it was junk. Low compression and almost zero oil pressure after warm-up. Pulled the engine again and discovered that all the camshaft lobes were gone. Lots of silver sludge everywhere in the engine...it was now junk. back to the engine rebuilder, asked a few questions (how was it primed, break-in, etc), once they were satisfied I knew what I was doing, they gave us another. Installed the engine, went to start and....damn, junk. One cylinder sounded like it had sand in it. Back to the rebuilder...third engine has been running great so far.
Sorry for the long winded story, but the rebuilder told us that every so often a camshaft does not make it through the break-in phase. He gets about 3-4 per year! It was the first time it has happened to me AND the first time I have not personally rebuilt the engine. I wonder if the reground camshaft was not properly re-hardened (nitrited?). Anyway, just curious.
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Posted By: GottaSki
Date Posted: July-18-2006 at 10:48am
He may get more. Yes a single lobe can go if the lifter fails to keep rotating and keeping the wear even. Not enough zinc in the new engine oil anymore for flat lifters. Roller lifters have been in service for decades preparing for this trend. Lots of failures occuring I understand.
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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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Posted By: 93SNautique
Date Posted: July-18-2006 at 10:54am
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I had a ProTech on my 93 and it was doing the same thing...backfiring on acceleration. I tried everything from filters, plugs, checked timing, even removed and cleaned the gas tank. And like you, i had the carb rebuilt which it didnt need. Finally went to a PCM certified mechanic who called PCM and they told him that the ProTech module was prone to cracking and could short to the block. Bottom line is that he replaced the electronic ignition which cost me about 500bills but the problem went away.
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Posted By: tommer12
Date Posted: July-18-2006 at 5:12pm
Thanks 92sNautique..... what did he he replace the ProTech with? Because it is my understanding that you can buy ProTech stuff any more.
I talked to my carb guy and he thinks that I should get new plug wires and have my altenator checked. He thinks that that it is possible I am not getting 12-14.1 volts I need to even run the computer when I am at idle. I'm not churning out enought at the alt to keep the ProTech even running correctly. The thing that I don't get is that I had the same stereo and amp, etc in it last year or at actually last two years, and no problems with power... other than a dead battery every so often. Which could be linked the alt not charging the battery enough from the draw on the stereo.
So if the ProTech is not getting enough power at idle, it could be not calulating the timing correctly out of the hole is what we think.
I looked for cracks in the Protech the other day and did not see anything visable.
thanks much fellas!
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Posted By: 93SNautique
Date Posted: July-18-2006 at 6:58pm
the mechanic replaced the ProTech with a whole new electronic ignition system that PCM sent him. He told me that it was the current model that they use on the new engines. I got a new distributor assembly, a new electronic module, and wiring harness.
I couldnt see the cracks on my ProTech either. they are too small but its a dielectric breakdown and was intermittent. The problem you describe sounds just like what i was seeing. backfire and popping while accelerating. and temperature seemed to affect it too. at a steady speed, it ran fine.
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Posted By: tommer12
Date Posted: July-19-2006 at 6:22pm
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Was your mechanic from a nautique dealer or a dealer that has contacts with PCM? I checked PCM's website and there is no contact information directly, looks I have to go through a dealer.
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Posted By: 93SNautique
Date Posted: July-20-2006 at 3:58pm
Skiers Warf Extreme in Osage Beach Missouri is the Correct Craft Dealer (Lake of the Ozarks) that i went to for the service. they told me their mechanic was PMC certified.
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http://www.correctcraftfan.com/diaries/details.asp?ID=1458" rel="nofollow - My 93
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Posted By: tommer12
Date Posted: July-21-2006 at 2:24pm
I called up West Coast Correct Craft and they said I may have gotten the wrong spark plugs from SkiDim. I told SkiDim the specs on my boat... 92 PCM 351, etc. Carb... They sent me Autolite 24. West Coast thinks they might not be hot enought at low RPM which cause the backfires to happen. I guess I didnt even second guess SkiDim and I am not sure what plug I had in there before.. I would have to hunt around my garage and look to see if I still have them.
So I'm going to try new plug wires and plugs and see, test my alternator for the correct voltage output, and go from there. Im cringing that the Protech would be bad..... just what I need is more parts to spend money on... yuk.
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Posted By: TRBenj
Date Posted: July-21-2006 at 7:46pm
Autolite 24's are the proper spark plug for your boat, assuming you have the standard 240 horse motor and not the 285hp ProBoss with the GT40 heads. I use Autolite 24's and my boat runs great- I dont think theyre part of the problem.
If you diagnose the problem to be the Protec, you have other options besides the kit that SkiDIM and PCM want to sell you. Check out a DUI by Performance Distributors. With this ignition upgrade and an Acme prop, my boat will keep up with a new 196 (330Ex) up to 35MPH or so. I picked up 200 RPM and a touch over a mile an hr. It would be the closest to a drop in replacement as you can get- it combines the distributor and coil in one housing. Price isnt cheap, by the time you get new spark plug wires, youll end up spending $400 or so. Still a very worthy upgrade, IMO.
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Posted By: 79nautique
Date Posted: July-22-2006 at 1:29am
if you have the pro-tec you don't use 24's the resistance is wrong for a DIS type system. Check the ref section manuals for the correct numbers, mite be wrong but???? it's late
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http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique
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Posted By: tommer12
Date Posted: July-23-2006 at 6:24pm
In my manual, I don't see anything with the autolite 24.... I do show Motorcraft brf3m or autolite btf3m. Then a side note about
14mm plug awsf22 = autolite 763. However.. I cant seem to find the 763, so I assume the the 764 is the replacement.
113 degrees, decided not to take the boat out and hide in the shade.. ugg
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Posted By: advsouthwind
Date Posted: July-26-2006 at 12:48am
IF YOUR ENGINE HAS BEEN BACKFIRING FOR A WHILE YOU HAVE PROBABLY BLOWN OUT THE POWERVALVE IN THE CARB/ MAKE SURE YOU CHECK THAT OUT GOOD LUCK
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gave up sea ray life for a 77 southwind 20 project just livin the dream
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Posted By: tommer12
Date Posted: August-06-2006 at 6:36pm
Sorry, i said 763, I meant 764. I put those plugs and it works perfect now. I changed to only running 91 octane also and I didnt have one pop at all yesterday pulling about 10 people wakeboarding full tank of gas..... It was nice to have her back again......
So my theory of the low amps at the low end was not it. I think it was a mixture of the wrong plugs and low 89 octane that start the back fires.
hope this helps someone else.
cheers
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