30 Missing and backfiring

"2 weeks ago my mercruiser 3.0

"2 weeks ago my mercruiser 3.0 started to make a very soft barely audible popping sound. Earlier in the day I had a hard time keeping it at idle in neutral. This condition only lasted for 20 minutes or so. Last week the engine ran fine for the whole 8 hours I was out. Today it ran fine for about one hour and then I started hearing a loud single pop like a backfire,every 2-3 minutes. I backed off the throttle to check things out and I never heard it again.About 4 hours later it started to act up again making the loud popping sound but now every 30-45 seconds. In addition I started to feel and hear what sounded like a miss in the engine. These sounds and misses are more prominent when going against heavy current or before planing off (heavier loads) I had a my marina install a new fuel filter/seperator and a carb filter and I also asked them to check for the popping . They said they could not verify it at the time, but this is also when the noise was very soft. Any Ideas"

What type ignition? What type

What type ignition? What type fuel system?

The fuel system has mechanical

The fuel system has mechanical style pump (not electric) According to the mercruiser website the ignition is an EST type with a distributor.

From the description of your p

From the description of your problem - I would think the place to start would be to check for water in the fuel filter.

The fuel/water seperator filte

The fuel/water seperator filter is 3 weeks old and I fresh gas in the tank. I filled it 2 weeks ago.

Tom- did you take the gas to t

Tom- did you take the gas to the boat or buy it at the marina? Have you taken a fuel sample yet? Was any other work done on the boat before this started?

"The gas was purchased at a re

"The gas was purchased at a reputal marina. No, I have not done any fuel sampling yet. The only work done in the last few weeks was an oil change, and the new filters. All season I have been treating my fuel with a Star Brite product called Star Tron because of the E10 hype. I also use my boat 8-12 per week or every other week so my fuel does not sit too long and have a chance to accumulate water. But I guess some "bad" gas could have been picked up when I filled up 2 weeks ago. Just last night I read an article where some field tests were done and they found that Star Tron is not doing what they have been claiming it woul do all season. The new thing that they claim works best is E-Zorb by MDR. Any comments"

"If this all started when you

"If this all started when you bought the gas from the marina, take a sample before doing anything else. If you have one, use a primer bulb and hose, like what is on an outboard. It's cheap and it works. If you can, raise the bow and tilt the boat to the side closest to the filler neck so the bad gas settles where you can get to it."

How long would it take for the

How long would it take for these symptoms to start after filling up. I have an 85 gal tank.I had 1/4 tank when I was heading back in and filled completely. I ran for about 20-30 minutes at about 3800 rpm back to my slip. The boat then sat for 2 weeks. Yesterday it didnt start doing this until after 1 hour of running. About 2/3rds the time at 3800 rpm and the other in no wake areas. How long does it take for "phase seperation to occur". This was also the only time I have not added any stabilizer all year because I did not have any on the boat.

"Unless there's a lot of w

"Unless there's a lot of water in the tank to mix with the ethanol, it takes more than 2 weeks. I would still do a sample. Less gas = more air and with temperature swings, the condensation/expansion/contraction cause the problems. It's an ongoing process, though. You may have had some in there but the new gas may have tipped the scales. Check your fuel/water separator and if it has cloudy gas in it or water droplets, you know where part of the problem is."

"Thanks Jim
Unfortunately du

"Thanks Jim
Unfortunately due to time constraints and having my boat at a marina an hour away. I wont be personally able to do this, I contacted my marina and they will be checking it for me. But thanks to your info I now know what questions to ask and have a better idea for myself of whats going on. Hopefully if it is water in the tank this will not be a large expense but just another one of the many many many many small expenses. Ill let you know how it turns out."

Also if anybody has any feed b

Also if anybody has any feed back on which is better as a treatment for E10 please post

Star Tron by Star Brite or E-Zorb by MDR