if you unplug it before starting the boat - there is a possibility of the engine not even starting. I guess 4 seconds is the timeframe this boat runs. Unpluging the IAC here could stall it quicker. Try unplugging it (2 people) advancing the throttle to see what happens. Do not keep doing this plugging and unplugging x amount times. Keep in mind when the IAC does show a real fault - the warning horn is 2 beeps.

Forgot the low pressure (boost) fuel pump the average psi range is 10 psi. The high pressure fuel pump readings are from 41 to 45 psi for an average of 43 psi. I just remember, I did not post it.

hell today was the first day it did not pour rain in a long while. I had to get back at it as well.

1. DID THIS boat ever run right after you changed the cap and rotor ? 2. It ran correctly before you changed the cap and rotor - is this correct ? 3. Are sure you did not move the HVS (distributor) - is the hold down clamp / bolt tight ?

go back to post # 27 and read # 8 that is listed.

The repair shop checked the shift in gear switch ? post # 27 - # 1 that is listed

Has anyone CHANGED the water pressure sensor as of yet ? Make sure you get a very current one. Solid horn - block pressure low - possible low water flow but IMO bad water pressure sensor - and it can be bad not open or shorted that's is causing it to not throw a code.

Go back to post # 8 as that was the first thing I posted from the get go and again in post # 27. I really thought you or someone might have changed it way before this timeframe ? That's why I did not bring it up again . Looks like no it was NOT changed - is this correct from your post 39 ? I WOULD REALLY CHANGE THE WATER PRESSURE SENSOR. Trying to cover everything and follow up with it.

BUP , I am a friend of Chaoscube and probably will try and go help him debug the boat on the weekend , About the low pressure boost pump , can It be bypassed ? Like plumb direct to the pressure pump ?

In my opinion it seems fuel related , it's too bad we don't have a video but the it idles steadily for like 2-3 seconds and then stutters and quits .... And when the problem started to show up it would idle steady for 20-30 seconds then do the stuttering then Buzzer / Quit ...

Btw I have printed out all the things you told us to look at and will help Chaoscube check everyone of them , after he here's from the dealership...

Low fuel pressure is not going to cause a solid horn going off. Yes it very POSSIBLE you have 2 or more problems going on. Solid horn is listed as severe and or critical fault(s).

here is a laymans test start the engine and throttle it as long as you can to keep it running. when engine dies - unscrew fuel filter - fuel should be spilling from the filter half way from loosen and completely full to the rubber O-ring when taken off. That is a laymans test to see if your boost pump can keep up to feed the high pressure fuel pump. If the fuel filter is only 85 % full or less you have a restriction or a low boost pump problem.

Have you guys tried running this motor on a portable fuel tank with new fuel, correct size fuel line and primer bulb inline - start motor and have someone keep squeezing the primer bulb - did the engine pick up and stay running ? or engine problem the same. These are things like I said process of elimination. separate your systems of the boat to pin point exactly where the problem is.

Solid horn is another problem for the running conditions. Again possible 2 or more things giving you the problem.

water pressure sensor very possible, I guess it has not been changed. Here is a tip - we keep sensors and switches on hand and really use them as diagnostic tools but they are used for more than just one boat / engine for testing.

I go to the dealer this morning...they called Merc and they said with all the procedure he did on the engine...its very probably the ECM. Merc will sent a used ECM 555 flashed for my engine to test it. If it works fine with this other ECM, I will have 3 options.

-order their $2000 brand new ECM (merc dont want to sell a used one)
-find a used ECM 55 and find someone to reflash it for my setup
-going carburated with a Edelbrock carb and intake

We'll see whats going on on next week when they got the reflashed used ECM...

OK thanks for the heads up. ECM of course are the last item on the list because most think they really never good bad.. That's not true. ECM can fail without reason but a lot times something caused the failure. I am not saying that a bunch of ECM fail all over the place but it does happen.

Just saying - wrong batteries - wrong connections, weak batteries, loose connections, voltage spikes do not help the ECM out. They really need constant voltage and the proper amount. Again changing the ECM with a good known one is another process of elimination to in fact getting closer to pin point the problem or to pin point IT IS THE REAL .PROBLEM for a fact. I have no idea what the dealer has done or not done here to pin point exactly. Like I said before it sounds like a possible lunch eater for you and them to pin point what is the real problem is taking place..

Please update this even if it does not fix it.

Update !!!

I go to the dealer today and ask them how they gonna receive the flashed ECM from Merc. They told me somewhere next week. I told them I need to pick the boat today to make some other interior work and a few things....so I go back to my shop with the boat. They told me they will call me next week when they get the ECM.

I replace the new cap & rotor distributor and turn the key on and the engine is running like new...like last summer. I dont know why I didnt think to switch this back before but the dealer were again telling me today that it was the ECM, if not the ECM after the test....they would be looking at each wire in the main big harness.

I'm soooo happy the problem is now solved. Just a little frustrated about the dealer that decided to charged me 4h of diagnostic when I bring the boat there for only a Scan Check and when they told me it will be $45 only. Now I owe them a bill of 4h at $100/an hour.... I didnt pay anything today when I pick the boat....we'll see tomorrow at the phone if the owner will deal something with me.

Thanks to all you guys who have submitted their ideas here about these problem.
Have a great summer !

...

Who's cap/rotor where the 1st ? And who's was the 2nd ?

I had an old dirty cap & rotor that worked well last year. I have decided to do some maintenance this spring and bought a brand new Sierra cap & rotor at the Marina. I changed these and it looks that they are defect out of the box. I switched back to old dirty cap & rotor I had before and it works fine ! Hopefully I kept the old stuff and not throwing it to the garbage.