Vibration/Miss at idle

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   Had the boat out this weekend and something wasnt right. Normally i run up to about 4800 rpm and 47 mph. This weekend could only muster about 4400rpm and 41 mph. I noticed a slight miss at idle and there was more than normal vibration.  Switched out props and no improvment.  

Before the weekend I changed out riser gaskets, belts and pulled the plugs. With 175 hours all plugs looked new so i reinstalled. I pulled them again on the water and at least one was wet w/ gas/oil.

Im thinking my 13 year old wires need to be replaced and maybe a set of plugs.

Anyone have any thoughts or ideas for me?

93 351 ProBoss 633hrs. Thanks Darrel

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Darrel Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: June-16-2004 Location: United States Status: Offline Points: 340	Post Options Post Reply Quote Darrel Report Post Thanks(0) Quote Reply Topic: Vibration/Miss at idle Posted: April-30-2007 at 5:17pm
	Had the boat out this weekend and something wasnt right. Normally i run up to about 4800 rpm and 47 mph. This weekend could only muster about 4400rpm and 41 mph. I noticed a slight miss at idle and there was more than normal vibration. Switched out props and no improvment. Before the weekend I changed out riser gaskets, belts and pulled the plugs. With 175 hours all plugs looked new so i reinstalled. I pulled them again on the water and at least one was wet w/ gas/oil. Im thinking my 13 year old wires need to be replaced and maybe a set of plugs. Anyone have any thoughts or ideas for me? 93 351 ProBoss 633hrs. Thanks Darrel

87BFN owner Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: August-25-2006 Location: Saline, MI Status: Offline Points: 2194	Post Options Post Reply Quote 87BFN owner Report Post Thanks(0) Quote Reply Posted: April-30-2007 at 5:32pm
	I would go with new plugs and wires. Make sure you check your gap on the plugs before installing. Not sure where your getting your vibe from. Did you check your alignment yet this year???? The cutlass bearing may have gone bad over the winter, check that too.

81nautique Members Profile Send Private Message Find Members Posts Visit Members Homepage Add to Buddy List Grand Poobah Joined: September-03-2005 Location: Big Rock, Il Status: Offline Points: 5796	Post Options Post Reply Quote 81nautique Report Post Thanks(0) Quote Reply Posted: April-30-2007 at 5:41pm
	Did you cross 2 plugs wires when you pulled the plugs? I would check the firing order first and then replace with new plugs and wires anyway.
	You can’t change the wind but you can adjust your sails

Darrel Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: June-16-2004 Location: United States Status: Offline Points: 340	Post Options Post Reply Quote Darrel Report Post Thanks(0) Quote Reply Posted: April-30-2007 at 5:44pm
	Thanks 87BFN, yes all gaps were/are .045. Cutless/strut/shaft replaced last fall did alignment at that time too. I think the motors slight miss is most of the vibration. I should probably be a little tighter on the alignment tolorance. 81, I dont think i crossed any wires, these are original wires. If i placed one wrong the next would be too tight to fit. Thanks

81nautique Members Profile Send Private Message Find Members Posts Visit Members Homepage Add to Buddy List Grand Poobah Joined: September-03-2005 Location: Big Rock, Il Status: Offline Points: 5796	Post Options Post Reply Quote 81nautique Report Post Thanks(0) Quote Reply Posted: April-30-2007 at 6:11pm
	Darrel, With all due respect, you said the boat has a miss at idle and it's down 400 rpm and you've got a plug soaked. You can check the alignment but it's not where your engine miss is coming from. What does it have for ignition system and when was it last tuned up?
	You can’t change the wind but you can adjust your sails

Darrel Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: June-16-2004 Location: United States Status: Offline Points: 340	Post Options Post Reply Quote Darrel Report Post Thanks(0) Quote Reply Posted: April-30-2007 at 6:56pm
	Yes i concur 81, the miss is the problem. I have the ProTech ignition. Plugs have 175 hrs on them in 4 years. Looked perfect til this weekend. Orig wires could be brittle/fragile? 2nd minor issue, I think my alignment is a very, very small part of my vib. issue, im out a couple extra thousandth at most. I wasnt clear above when responding to 87BFN.

81nautique Members Profile Send Private Message Find Members Posts Visit Members Homepage Add to Buddy List Grand Poobah Joined: September-03-2005 Location: Big Rock, Il Status: Offline Points: 5796	Post Options Post Reply Quote 81nautique Report Post Thanks(0) Quote Reply Posted: May-01-2007 at 7:04am
	Someone with a background on the Protec should chime in, I know nothing about it but it is suspect after that many years.
	You can’t change the wind but you can adjust your sails

Munday Members Profile Send Private Message Find Members Posts Add to Buddy List Gold Member Joined: August-17-2004 Location: United States Status: Offline Points: 538	Post Options Post Reply Quote Munday Report Post Thanks(0) Quote Reply Posted: May-01-2007 at 7:45am
	If the pro tec fails you lose 2 cylinders.Run compression test on cylinder with bad plug and another on same side.Several on this site have had cams go flat(i'm one of them)these are same problems I had when I diagnosed mine.Have you been running syn. motor oil? good luck Munday

Darrel Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: June-16-2004 Location: United States Status: Offline Points: 340	Post Options Post Reply Quote Darrel Report Post Thanks(0) Quote Reply Posted: May-01-2007 at 2:14pm
	No syn oil, just valvoline racing oil. So... if i lost 2 cylinders its because each coil pac handles 2 cylinders? Looks like i will first replace wires with skidim product unless someone has a better reccomendation on where to buy or a better wire.. I will bring compression tester and pray its not a coil pac or bad cam. thanks

64 Skier Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: February-08-2004 Location: United States Status: Offline Points: 415	Post Options Post Reply Quote 64 Skier Report Post Thanks(0) Quote Reply Posted: May-01-2007 at 6:20pm
	I noticed my '95 Tahoe running slightly rougher than usual even after routine tune ups. Changed the 12 year old wires and coil and now the engine idles smoothly. Regardless of a possible ignition issue; you have a lot of hours on those wires and coils degrade over time.
	64 Skier 66" HO VTX and 67" HO Triumph 71CC

Darrel Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: June-16-2004 Location: United States Status: Offline Points: 340	Post Options Post Reply Quote Darrel Report Post Thanks(0) Quote Reply Posted: May-02-2007 at 5:27pm
	Talked to Richard at skidim, and ordered new wires. Found the autolite 764's local for $12/ set. Thanks for everyones help...let ya know if it cures all.

Darrel Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: June-16-2004 Location: United States Status: Offline Points: 340	Post Options Post Reply Quote Darrel Report Post Thanks(0) Quote Reply Posted: May-21-2007 at 5:10pm
	Replaced wires first, still had the miss. Put in the new plugs and it ran perfect! Guess a bad wire fouled the one plug that was soaked. Thanks for everyones help.

David F Members Profile Send Private Message Find Members Posts Add to Buddy List Platinum Member Joined: June-11-2004 Location: United States Status: Offline Points: 1770	Post Options Post Reply Quote David F Report Post Thanks(0) Quote Reply Posted: May-22-2007 at 10:32am
	Darrel: More than likely what happened is that you broke (small crack) the plug (that was missfiring) when you removed it the first time and never noticed it.

Vibration/Miss at idle

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