What might this be? 3.0 coughs once in a blue moon... Fixed I think...

[TwoBallScrewBall]

Boat runs great. This has happened twice now...<br /><br />I'll be humming along at about 3500RPM, and the engine will emit a "cough" or a quiet backfire, miss just a beat, then resume normal operation like nothing ever happened. It loses power for just that split second, then jumps right back and keeps on going. Has happened twice, both times at cruising speed, different days, different loads, different gas, only constant is the approximate throttle position and the sound it makes when it happens. I'm thinking it may be losing fuel but there are no apparant problems, carb is a fresh rebuild that I rebuilt and inspected myself, all fuel filters are brand new and I added a filter/water separator at the beginning of the season. <br /><br />Engine is brand new this season, electronic ignition, and other than this problem which really isn't a problem (yet) it starts and runs absolutely perfect.<br /><br />Any ideas?

 

[crazy charlie]

Re: What might this be? 3.0 coughs once in a blue moon... Fixed I think...

Take off the fuel water sep and drain it out and see if there is some water in there.Charlie

 

[hoot]

Re: What might this be? 3.0 coughs once in a blue moon... Fixed I think...

last summer a similar thing occurred with my boat. running along, boat sputtered, kept on going, we looked at each other like did that really happen? did it again. later in the day, completely shut down, no power anywhere. found an old inline buss fuse that had blown in the igniton circuit.

 

[TwoBallScrewBall]

Re: What might this be? 3.0 coughs once in a blue moon... Fixed I think...

Yeah, hoot, that's what I'm afraid of. The "later in the day" scenario you dedscribed. <br /><br />Charlie, I'll do that tomorrow if the monsoon lets up here and let you know what's in there.

 

[TwoBallScrewBall]

Re: What might this be? 3.0 coughs once in a blue moon... Fixed I think...

Well I checked the separator, no water. Has done this now and then but now tonight over a span of about 2 hours it did it twice. Now I'm getting worried more as it's never done it twice in one outing before. I checked simple things like plug wires, carb studs, wiring harnesses, etc, can't find anything obviously wrong. Any other ideas? Could it be the carb? I rebuilt it myself over the winter. It was straightforward and I've rebuilt lots of carbs from dirtbikes to quardajets with good results in the past, and was really careful with this one since there's no walking home if it breaks down. Any suggestions on what to check would be much appreciated. I noticed today it happened at "just over planing" cruise speed and at almost WOT. Never ever ever happens at low RPM. <br /><br />Thanks!

 

[Bondo]

Re: What might this be? 3.0 coughs once in a blue moon... Fixed I think...

I've seen a Coil, Take a Dump in the Exact Same Manner...........<br /><br />Hey Steve, I Like the boat name ......

 

[TwoBallScrewBall]

Re: What might this be? 3.0 coughs once in a blue moon... Fixed I think...

Thanks Bondo. <br /><br />I hope it's not the coil, it's a new EST coil, don't know how much they cost. I'll double check my wiring job, maybe I have an intermittent connection problem on one of my wires.

 

[cobra 3.0]

Re: What might this be? 3.0 coughs once in a blue moon... Fixed I think...

A Pertronix Flamethrower II 'hot' coil would go for about $40.00. (The epoxy filled version is suggested for marine use.)

 

[Elk Chaser]

Re: What might this be? 3.0 coughs once in a blue moon... Fixed I think...

If all that has been changed is the carb then I would suspect that it is the problem.

 

[TwoBallScrewBall]

Re: What might this be? 3.0 coughs once in a blue moon... Fixed I think...

Nope, everything is new or rebuilt. Put the new long block in, new EST dist, new coil, new plugs, new wires, rebuilt carb...<br /><br />The coil is the Delco EST coil.

 

[achris]

Re: What might this be? 3.0 coughs once in a blue moon... Fixed I think...

If the engine cover allows water ingress, start looking for water on electrics. Had a similar problem with mine and it turned out to be water dripping onto the shift cutout switch. Easy to fix, a real pig to find. <br /><br />Chris..........

 

[marunr]

Re: What might this be? 3.0 coughs once in a blue moon... Fixed I think...

Mine did that last year and got worse little by little until the engine would stop long enough for me to mess around with the wires. It was corrosion in one of the 50 amp fuse holders, causing a bad connection. Replaced it and it was fine.

 

[Galloping Ghost]

Re: What might this be? 3.0 coughs once in a blue moon... Fixed I think...

there is a small possibility that the timing is a wee bit off and it is backfiring through the carb.

 

[rtrippleclick]

Re: What might this be? 3.0 coughs once in a blue moon... Fixed I think...

I had the same problem. It drove me crazy half the summer. After I rebult the carb and changed the plugs, wires, pick up mod. etc. The problem was a wire that was coming loose from the eyelet that was fastened to the ignition switch. It finally fell off then I found it. Start the motor and move the wires around on the ign. switch.<br />Good luck,<br />Bob

 

[TwoBallScrewBall]

Re: What might this be? 3.0 coughs once in a blue moon... Fixed I think...

OK I think I might have found something regarding this. <br /><br />I checked wiring, plugs, everything I could think of. Found nothing. Then last night after resurrecting my boat from the flood (see other post regarding sinking in the driveway) I decided to try an old trick and check for intake leaks around the carb with some starting fluid. Bingo! When I sprayed around the base gasket on the inboard side of the carb the engine started missing/stumbling a little. Going to replace that gasket and while I have the carb off go through it again to double check the setup. Do you think that maybe this slight carb base gasket leak could be the problem?

 

[TwoBallScrewBall]

Re: What might this be? 3.0 coughs once in a blue moon... Fixed I think...

Found two problems. One was the slightly leaky carb base gasket. I tightened down the carb again and put a small smear of sealant around the spot where it seemed to be leaking to the point where it would no longer change RPM when I sprayed it with starting fluid as a temp fix until I get a new gasket. <br /><br />Also, my choke is not working at all. Just noticed when I was playing around near the carb. Must have missed something when I reassembled it in April. I have had no problem starting the boat at all, but the choke flap is totally loose, just freely flaps back and forth. At rest, it was sitting about 20% closed I guess. But the problem was that the slightest touch could close it. I think what was happening was that at speed bouncing around, it would momentarily slap shut then re-open, and at higher rpms this was causing the little cough I was experiencing. I tied it open (with string) as (another) temp fix and have been out 4 times now, one time used about a half a tank of gas just blasting all around the bay for a few hours, and not a single problem (yet). I'm pretty confident that it's fixed. <br /><br />Thanks again everyone.