The main pump on the port side is almost impossible to get to.

I changed th IAC today and eliminated the alarm. Real test will be when the rubber hits the road....:rolleyes:

Good luck!

I believe that each fuel pump has its own power relay located next to the PCM and plugged into the wiring harness there (~1" square black plastic). They are easier to get to than the pump power connectors.

What kind of crud are you finding in the injectors? Grit? Goo? Similar crud in each injector or just some of the injectors? Any conclusions as to where the crud is coming from?
You say "this year". Do you find this crud every year?

I had fuel issues last year after the state went to Ethanol May 1st 2006. I suspect the tank had some water in there, and consequently when Ethanol was added it slowly went to crap. Went thru a boost pump on each engine. One sudden, one gradual. I suspect it happended due to the pump gulping water or crud, and fried. Water separators in the beginning kept coming up with water and some crap. Eventually they cleaned up perfect. I ran my tanks down practically on fumes for the winter storage (conventional wisdom for Ethanol long term storage). First start up of the year and the starboard motor ran sluggish and hard idle. Read here on the board that someone else popped their injectors out and found the same fine grit. So I held my breath and dove in. Sure enough 7 out of 8 injectors when turned over and tapped, gave up a fine reddish grit in each. I then sprayed each out with a plastic safe electrical contact cleaner with the little spray straw and re-installed. Motor then purred like a kitten.
The other motor started chugging a little during a poker run a couple of weeks ago when my alarm issue started. So reasonably I could deduct if one was dirty, then chances are the other was too. I popped them off, and sure enough the same thing. Now it too purrs like a kitten.

I "suppose" the fine gritty stuff is most likely fiberglass dust or something that may have contaminated the tank during the build process, and when I ran the tank almost dry for storage, the line began sucking it up. It probably had sucked up a little over the course of the last couple of years, and running it way down dealt the final blow. The grit was fine enough to make it thru the inline filter (not really that much filtration, like 60 microns), thru the boost pump screen (only really filters out the big stuff), and made it past the separators not the injectors. I also took the line off the boost pump and sprayed out the boost screen to be sure it was clean with no signs of anything coming out.

BTW after replacing my IAC valve, I decided I'd take the spare I got and go ahead and put it on the other motor to have two new IAC's running and keep the old "good" one a spare. Low and behold after I take it off the other motor, I found a long swirl of melted plastic (I'll post a pic later) near the connector where that one too, had at some point overheated, yet had not failed completely "yet". Probably would've during the next time out (it makes me wonder why did they get hot?). It's been a real head scratcher and PITA, but also a good learning curve, and a motivator to go ahead and get my own scantool. The tool also discovered my engine meters were reading over 10 hours "more" than the ECM had in terms of operating hours. So I unplugged them to let the engine catch up with the what the meters show.

Pressure drop of Racor B32020MAM WSFF, 10 microns @ 60 GPH rating= 0.61 psi.

Pressure dropof Yamaha MAR-FUELFIL-TR WSFF,10 microns @ 90 GPH rating= 0.25 psi.

Pressure dropof Ramco 300M WSFF, 5 microns @ 120 GPH rating is "~<1"Hg"= ~<0.50 psi.

Pressure drop of Merc 35864572T inline filter,116microns @235 lbs/hr=(38 GPH)=<0.20 psi.

Pressure drop of Merc 35-802893T WSFF, 25 microns per Merc which is Champion 802893-1(Champion could not ID this OEM number but their cross ref for the OEM Merc filter number was PFF3808 which is....rated 27 microns at 50% , 36 microns at 98% of element & 90 GPH but spec is 0.20 psi loss at 50 GPH so @ 'est 50' GPH= 'est 0.20 psi'.

Reportedly the 496HO fuel injector screens are 2-3 microns.

I currently use the 10 micron Yamaha WSFF which also holds a lot more water than the stock Merc filter. If and when I can figure out how to adapt my fittings to accept the 5 micron Ramco that will be my filter.

Are you referring to the water separator?

I wonder if the clogged injector screens may have forced the IAC to operate at a higher duty cycle (they normally run around 25-30%) to achive the desired idle speed, and thus the higher temps.

Yes, except for the inline fuel filter mentioned. The others are two filters in one. A water separator and a fuel filter.

Dave good question. I'm gonna be keeping my eye on them and sniffing for any future heated plastic odors in case there's something lingering.

Rage does it screw into the same housing as the standard separator? Send me the online ordering info if you have it, or where to go and get it. The standard Merc separators are crap for the fine stuff.

The Yamaha filter is for the Yamaha out board motor remote mounted water seperator fuel filter systems but the filter is a perfect match for the Merc filter mount. The Yamaha filter is however half again longer than the Merc filter so check that for interference. I had enough room to install as a direct replacement.

The filter is available from any Yamaha OB motor dealer which is where I go. Do not know if it is available elsewhere.

The Ramco filter is not a direct replacement. I am looking for a work around to get it to fit. That will require some mods or pay the price for the complete Ramco remote fuel filter system.

Reckless:
That difference in engine hours is because the ECM only records actual running time, not "key on" time. It's normal for the hour meters to be a little higher.
Ed

Ed yeah i know. Just wasn't expecting a 9 hour difference in key time.

Well this past weekend I took the boat out overnight to Norfolk's Harborfest. The 2 beeps per minute alarm returned, though this time only intermittently and only once above 4k rpm did the full alrm kick in (never full guardian). I ran another scan upon my return home Sunday and it came up showing IAC output again in the history, and it showed at idle on the hose IAC Output code is "inactive" when running faults no alarm during the scan except when I pumped the throttle a few times, from PCM Data? I did notice when checking the water pressure it would go from like 3.5 to showing like 43-50 psi? Some times when I pumped the throttle it would reduce back down to below 10 psi range.

Any resloution to the alarm?

I am having the same problem on a 496. Impeller was burned up. Replaced it but am still getting the 2 beeps then the long beep when trying to run. Also cutting out at 4000 rpm. I am checking the IAC, to see if mine is burned as well. I will let you guys know.

Also my engine is stock no mods at all and only has 54 hours on it. So I don't think any of your mods caused the problem. Now when the impeller burned up the temp gauge was fine but the exhaust manifiolds of course were hot. Are there manifold temp sensors? I am new to boat engines so this maybe a dumb question, so please forgive the learning curve. :D Is it possible that both the IAC and the exhaust sensors burned when the manifolds over heated?