Random Miss at Idle. HELP!!

[Hicktacular]

Joe54

I may do that with the timing light, but some of the threads that I have read in says that it is common for a weak coil to send enough to light a timing light, but not enough to run correctly.. I am not sure if that is true though. If it is, i could see that being a false positive for testing a coil.

[EuropeanAM]

You're really not performing a KV test with the timing light- merely using it to see if there is spark present (or not).

[Hicktacular]

You're really not performing a KV test with the timing light- merely using it to see if there is spark present (or not).

I see. I tried it today and could not really tell if it was happening. It was idling really good on the muffs. Seems to only be present in gear, at idle... I may try it on the trailer, at the ramp. Just putting it in gear and swap the connection around onto the different plug wires.

Also, I bought a new coil today. According to the package, it is the same part number. Stamped on the side of the coil, it has Rev C. The other coil that I bought a week or so ago for the same engine, says Rev A. I checked to see if this new coil ohms as the others do, and had no resistance from the plug tower, to pin C. Zero. I called the store I bought it from, and they said not to worry about it, that it was a bad way to test a coil... but that is how the manual says to do it, so I am confused.

Should I be worried about the different Revs (Rev A vs Rev C) on the two new coils? I am attaching pics of the new coils.

Should I be worried about the newest coil have no resistance, where the manual says that there should be?

[Riccochet]

You can put it in gear on muffs

[Hicktacular]

You can put it in gear on muffs

I have, but I believe the engine being under a little load is what is allowing me to hear the miss. The miss is probably there out of gear, I just can not hear it as well. Although I did not notice any cylinders that had a inconsistent strobe on muffs....

[EuropeanAM]

As long are both 8M0077473 coils (as printed on the bag), the production revisions are irrelevant. Especially since the package dates are about 7 years apart.

[Hicktacular]

As long are both 8M0077473 coils (as printed on the bag), the production revisions are irrelevant. Especially since the package dates are about 7 years apart.

Thanks! I'll get it in the water tomorrow to see if it helped. If not, could the computer be the next step, or do you believe the flywheel is still suspicious?

[Hicktacular]

I rented a fuel gauge from auto zone. It isn't liquid filled.. will it work well enough? Is there a cheapish set that will work that anyone would recommend?

[JOE54]

I don't know of cheaper ones

[Hicktacular]

I don't know of cheaper ones

The auto zone ones are showing 75/85 air fuel. +/- 2psi. The are not bouncing terribly. 85 is low on fuel pressure. Right?

[EuropeanAM]

Must be a liquid or glycerin dampened, DUAL pressure gauge. You cannot trust one that is not.

[Hicktacular]

Sad to say that the coils didn't help.. what is a good price for diagnostics? Also, would that include air and fuel checks?

[JOE54]

afraid of that, depends on how long and how bad tech wants to find out whats wrong, sure should include that and every thing else, I know what id do, drag it SC you know who

[Hicktacular]

afraid of that, depends on how long and how bad tech wants to find out whats wrong, sure should include that and every thing else, I know what id do, drag it SC you know who

Agreed. I may see about a road trip!

[EuropeanAM]

I mean this in the most respectful of ways: As the owner of the boat, you should expect to pay him for his time and expertise. You shouldn't have to pay for the time it takes for someone to learn about the basic systems, however.

[Hicktacular]

I mean this in the most respectful of ways: As the owner of the boat, you should expect to pay him for his time and expertise. You shouldn't have to pay for the time it takes for someone to learn about the basic systems, however.

I agree 100% Don! And have no problem doing that. What I don't want to do is pay someone $100 an hour to guess, and buy parts. I figure I can do that free of labor I respect the knowledge and expertise you guys have. That is why I am so grateful for the help I have received here. Twice this boat has been in the shop since 2008, and both times I walked away thinking I was short changed. That is why I am hesitant. I am going to see if I can get some good gauges (I should have started there I guess) and that will be my last effort. Unless it points us into an obvious direction.

[06 SB]

I agree 100% Don! And have no problem doing that. What I don't want to do is pay someone $100 an hour to guess, and buy parts. I figure I can do that free of labor I respect the knowledge and expertise you guys have. That is why I am so grateful for the help I have received here. Twice this boat has been in the shop since 2008, and both times I walked away thinking I was short changed. That is why I am hesitant. I am going to see if I can get some good gauges (I should have started there I guess) and that will be my last effort. Unless it points us into an obvious direction.

How far are you from Greenville, SC? It may be worth the trip to have Don put his hands on it.

[Hicktacular]

How far are you from Greenville, SC? It may be worth the trip to have Don put his hands on it.

A little over 5 hours..

[SilverFox579]

A little over 5 hours..

And worth every single one, both ways, to have Don solve your engine problem.

[Hicktacular]

I called a couple of local places. Both told me around $50 to run diagnostics. I took it to one today, and they said no current codes. I had one alarm that was an overheat. 164 degrees I think. I believe it was when I was adjusting the JP, trying to get the RPMs up. I was already having the issue before then, so I don't think it hurt anything. I did learn my lesson though. They also check the fuel and air pressure. They said they were both good and 10 psi apart. Basically said that as far as the computer knew, it was all good. I asked about a print out, and was told it would be a blank sheet of paper since the computer was happy...

Isn't there a deeper diagnostics than just checking codes? Maybe I asked for the wrong thing. I was pretty happy with them checking the pressures though. Saves me from having to buy a bunch of stuff to build my own set. I could not see the air gauge, but the fuel appeared to move between 88 to 91 psi. For $50, I may take it to the other shop. They are on the lake and would be easier for me to have it tested while warm. It seems more prominent then. He also turned each cylinder off to prove that they are all firing, and they were... I mentioned to the mechanic that I had a reed break a while back, and that while working on all of this, I had pulled the MAP sensor and it had oil and some debris on it. He said that he had seen some go out and do weird stuff.. so I ordered one. Probably will not make a difference, but sounded like it would be his first guess. I also took the 23P off since 5100 is my max RPM and I know that is too low. I put my 21P Laser back on. I don't like that prop, but it will free the engine up, in case that is contributing to the problem. I am looking for someone to trade the 23P for a 21P Tempest.