backfiring @ high RPM’s
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=869
Printed Date: November-22-2024 at 9:41am
Topic: backfiring @ high RPM’s
Posted By: Guests
Subject: backfiring @ high RPM’s
Date Posted: September-28-2004 at 6:11pm
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A friend's '83 Ski-Nautique Correct Craft has recently developed a nasty propensity to backfire and pop above 3200 RPM's. If you back off the throttle slightly, it gets worse, and starts popping louder and more frequently. You have to throttle back to about 1500 RPM's, and she runs smooth again, and can be revved back up to 3200 RPM's with no problems. There is evidence of some slight pinging that develops at about 3200 RPM's, just before the onset of the popping. He regularly runs 92 octane fuel in the boat. I suspect it's a timing issue. Boat has new points and condensor. What should initial timing be set for? Heard somewhere that it might be 6 degrees BTDC, but just want to confirm. Also, is there a reasonably priced means of converting to electronic ignition? Will an automotive Electronic Iginition system work on a PCM engine? Thanks!
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Replies:
Posted By: 79nautique
Date Posted: September-28-2004 at 7:35pm
It sounds like the mechanical advance is out of wack. The base timing should be 8-10 btdc the manual I have says 10 but I have seen 8 and 6 btdc. Also check and make sure that the mechancal advance is working correctly. You should not have over 35 degrees total advance at say 3000-3500 rpm if you do then that is your problem. Check the springs and weigths under the plate that the points are mounted to and you will see the mechanical advance. Also check the dwell before you set the timeing. the gap is .018" and dwell is 24-29 degrees.
I would recommend changing to electronic and getting rid of the points and I do not suggest using automotive for marine applications, if you do, you are take a big risk of blowing the motor box off.
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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: Jim_In_Houston
Date Posted: September-28-2004 at 8:59pm
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If this was an auto I would suggest the cam timing chain jumped a link. But, I'm new to the marine world so I will keep quite on this.
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Posted By: SS 201
Date Posted: September-29-2004 at 8:49am
Motors are motors, Basics are the same. If it pops thru the Carb it's on intake side, thru the exhaust it's on the exhaut side.
Then look for the troubles based from that anology.
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Posted By: Guests
Date Posted: October-01-2004 at 1:01pm
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I concur with 79Nautique, make certain BOTH the heavy and light advance springs are in place, and the mechanism is operating smoothly.
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Posted By: Guests
Date Posted: October-06-2004 at 10:19pm
Just a follow-up.
First of all, thanks to all those who responded. These forums are a fantastic place for the exchange of good information. It's nice to tap all of the brilliant minds out there for free advice.
Turns out, the problem with my friend's boat was indeed timing. Went to Sears, and bought their $70 Advance Curve timing light. Discovered that at idle, the timing marks were off the scale! Set the initial timing for about 8 degrees. Verified the mechanical advance was in good working order (total advance hopped between 30 and 35 degrees), and took her out. With two big adults on board, the boat revved quickly up to 4500 RPM with no knocking, pinging or backfiring! We achieved a top speed (confirmed by GPS) of 46MPH...WOW!
Thanks again for the help on this!
Jason
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Posted By: Guests
Date Posted: October-07-2004 at 10:33am
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Good to hear, even better to hear he didn't frag a piston or valve with the timing like that.
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Posted By: 79nautique
Date Posted: October-07-2004 at 2:05pm
I would concider upgrading to electronic ign in the off season and you won't have to mess with timming hardly at all. With points and condenser you will need to check timing and dwell often. But glad to hear she's running strong.
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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: Guests
Date Posted: October-07-2004 at 5:44pm
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My friend desparately wants to upgrade to electronic ignition, but doesn't want to pay $500 to do it. There seems to be no source of reasonably priced electronic ignition upgrades for this motor...which frankly, strikes me as odd, seeing as how it's a fairly common Ford engine. I'm a Mopar guy, and I think this is the first instance where I've found a part cheaper in the Mopar world than in the Ford/Chevy realm. Mopar performance sells a complete swap kit for $180. Perhaps it's the "Marine Engine" spectre that makes them so expensive? I don't know. Would appreciate any thoughts you all might have on finding a kit for this motor that won't break the bank.
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Posted By: 882001
Date Posted: October-07-2004 at 6:21pm
www.vintageperformance.com will have the setup for that boat for the conversion kit and hi perf coil for 100.00. all you need to know is if has a screw down or clip down cap. the install is 15 mins
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kemah texas
http://www.correctcraftfan.com/diaries/details.asp?ID=163&yrstart=1986&yrend=1990 - 1988
skinautique "2001"
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Posted By: IrishFooter
Date Posted: October-09-2004 at 6:06pm
Recently had some issues myself and I wonder if it is advisable to upgrade to a new distributor. There is a mallory with electronic ignition for $200 available from Summit Racing- not marine. The pins that the advance weights sit on were very loose and I peened them down to tighten them up. This advance still is not quite perfect.
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1979 Ski Nautique
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Posted By: 79nautique
Date Posted: October-11-2004 at 12:36pm
You can get a marine version mallory from summitt racing for around $325. there is a high perfomance HEI unit as well but it's a little more expensive. Or you can get the conversion kit for around 100 buck.
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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: Rick
Date Posted: October-11-2004 at 10:46pm
I'd stick to the conversion kit I did my 66 Barracuda after the rebuild. Just cleaned the machanical advance added the Pertornix module and it started every time.
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http://www.correctcraftfan.com/diaries/details.asp?ID=250&yrstart=1996&yrend=2000%20" rel="nofollow - 2000 Ski
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