Backfiring at 4000rpm's???

[codyandamber]

1991 mastercraft <br />351 pcm<br />direct drive<br />points system<br />400 hours<br /><br />When pulling a skier out of the water or running about 4000rpm's the boat has a slight backfire.<br /><br />Also at slower speeds it tends to have a little bit of a miss also. It is barely noticable. <br /><br />I have cylced through about 3 tanks of gas since this started.<br /><br />In the last 75 hours nothing has been replaced other than oil and tranny fluid.<br /><br />Where should I start?<br /><br /><br />Thanks to all,

 

[tommays]

Re: Backfiring at 4000rpm's???

full tuneup and fuel filters<br /><br />tommays

 

[Dunaruna]

Re: Backfiring at 4000rpm's???

Originally posted by tommays:<br /> full tuneup and fuel filters<br /><br />tommays

Including spark plug wires, at the very least - test them.<br /><br />Aldo

 

[Richard Petersen]

Re: Backfiring at 4000rpm's???

It will be the start of a sparkplug begining to fail. Your description is perfect. If not, check or replace the ignition points. Set the gap right on.

 

[codyandamber]

Re: Backfiring at 4000rpm's???

Sounds good to me. Thanks again for the advice.

 

[Reel Poor]

Re: Backfiring at 4000rpm's???

If you can notice a miss at slower speeds, see if you can determin which cylinder is missing.<br /><br />Before doing a tune up you may want to do a compression test.

 

[jeff13601]

Re: Backfiring at 4000rpm's???

The tune up will prob do it wonders. Make sure you set the points with a dwellmeter. Also look at the plugs when you change them to see how they look

 

[codyandamber]

Re: Backfiring at 4000rpm's???

Electronic ignition is on the way. Plugs didn't look too bad. The plug wires were getting a little worn. <br /><br />Once again, thanks for the feedback