[Putershark]

Originally Posted by jergofish

The boat and engine have performed flawlessly with the exception of the pure gasoline in Mexico being much richer than the gasahol we pump here in California, causing the engine to run rough on start up. I would have thought that the computer chips in the the engine would have corrected the fuel/air mixture to accomodate the pure gasoline.

That is a classic description of a "cold" start problem... Cold you say? yes... Here is the possible cause. You are starting to get deposits building up on the back side of the intake valves. These carbon deposits when cold soak up fuel. So when you turn the key on and it reads the warmer air temps from being further south, the ECU (like a choke of days past) does not dump in very much fuel for starting and some of what is dumped, is soaked up by the those carbon deposits. The problem goes away as the engine warms up and the carbon becomes as hard as a rock, but I have seen cases of the engines starting and stalling out many times till that temperature was reached from all the carbon build up... How to fix such well you have several options

1. Move to Canada since the ECU will pretty much always dump in enough fuel for starting in such conditions (too funny I know)
2. Remove the slowly building carbon deposits through the use of fuel additives. I recommend using Techron in clean up version bottle dumped right into the fuel. http://www.chevron.com/products/prod...ate_plus.shtml and have always had good success with using this product. Yamaha markets the same product, but calls it "Ring Free" and works well on both 2 (though in different areas) and 4 stroke engines.

Carbon though builds up inside your engine that have been using lower quality detergent fuels. When you shut the engine down, fuel "boils" away it leaves these deposits behind... This is why I only use high grade detergent fuels in both my truck and will only run Chevron fuel in my boat engine with it many times being 93 octane just because it is so hot outside. Engine Octane requirements is a different subject matter altogether

One other thing you can have checked, is the operation of the fuel injection system by the dealer to make sure all the sensors are working per design spec... The ECU though does NOT have the ability to compensate for carbon build up since no sensor to date can measure such... The EPA regulates engine builders to meet certain emission levels after so many seconds of start up, and usually the builders will set them even a little leaner just to make sure it will past those test... So even smaller amounts of carbon build up on the valves can have such effects even on marginal days. Also remember that the more intake valves you have on your engine, the more surface area you have to "grow" such carbon. This so a 8 valve 4 cylinder engine, may not show the same effects as fast, as say 16 valve 4 cylinder might

Hope this helps?