Miss first 15 minutes of running

[kenimpzoom]

Guys,<br /><br />1993 SeaRayder with 90 HP Mercury (Force) Sport Jet<br /><br />This has happened the last two times I took out the boat.<br /><br />It has a bad miss the first 15 minutes of running, then runs great the rest of the day.<br /><br />It starts easily and idles fine. Never stalls. Just has a bad miss at all engine speeds.<br /><br />I have filled the gas tank up both times right before I put the boat on the water.<br /><br />I think I have an idea what it is, but would like to see what you guys think it is.<br /><br />Thanks,<br /><br />Ken

 

[Jack Shellac]

Re: Miss first 15 minutes of running

Sounds like a plug may be fouled and is cleaning up a little as the engine runs. Second choice is a plug wire arcing to ground somewhere.

 

[JB]

Re: Miss first 15 minutes of running

Cold failing powerpack.

 

[kenimpzoom]

Re: Miss first 15 minutes of running

Forgot to mention that it is a brand new powerpack and I borrowed a powerpack from a buddy and had same problems.<br /><br />It has also been totally rewired and new plug wires and still has same problem.<br /><br />Before the second time it did this, I pulled the carbs and blew through every orfice and jet with carb cleaner and there was zero gum in there, only a few small pieces of sediment.<br /><br />It only seems to be missing on one cylinder. Dont know which one.<br /><br />My idea is that it is water in the gas. Condensation forms in the tank as I usually store it with tank close to empty. Once the small amount of water runs through the engine, it clears up. All the water ends up in the lower carb (its an inline 3 cyl) making only that one miss. What do you think?<br /><br />Ken

 

[kenimpzoom]

Re: Miss first 15 minutes of running

^

 

[jetdriven]

Re: Miss first 15 minutes of running

A good starting point may be to take a timing light with you the next time you have it in the water in order to figure out whether or not you're losing spark when the missing is occurring. Check each cylinder. If you're not losing spark, it's probably fuel related or a bad sparkplug. Good luck.