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Old 11-09-2011, 03:06 AM   #1
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Default Optimax 150 High Revving at idle on startup

Here is the scenario.

Over the past few weeks, one of my 2 x 150 Optis has been high revving on startup and then dieing. A subsequent start would proceed with a regular startup and idle. This has been generally happening after a trip or at a cold start and not all the time. This morning, as I went to start the engine for the first time, it idled normally for a couple of seconds and then it surged without stopping, so much so that I had to switch the key ignition off. Any subsequent attempt to restart the engine produced an immediate surge and over revving that can be only stopped by switching the key off.

I did not have the DDT with me and I have been unable to check the parameters but I did a full check only last week and everything was fine with no errors. I have also tried adjusting the accelerator and gears a few times but it hasn't made any difference.

Can anyone shed some light on what could be wrong? The pulse fuel pump diaphragms were replaced only a few months ago`, so I would exclude this.

I look forward to some feedback.

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Old 11-14-2011, 03:44 PM   #2
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Default Optimax 150 High Revving at idle on startup - SOLVED

Here is the Update ......
Last Saturday afternoon I finally got a chance to work on my boat and I was able to troubleshoot this issue. As I approached the problem I had 3 possible solutions in mind:
1) A tear or pinhole in either the Tracker Valve or Fuel Regulator Diaphragm
2) A stuffed ECM
3) A required recalibration of the Throttle Linkage and TPS
I proceeded in the above order.
1) Having 2 engines I started by hooking the Fuel/Air Pressure gauges to the engine working correctly and without starting it I tried placing the ignition in the ON position. The Air pressure gauge did not move but the fuel one went immediately up to almost 50 PSI while the Fuel Pump made a noise and then settled to just over 20 PSI. When I switched off the ignition the Fuel Pressure dropped slightly and then remained stable at around 20 PSI. When I repeated this test to the Engine that manifested the problem I obtained similar results with the exception that the Fuel pressure with the ignition ON stabilized at around 18PSI and after turning the Ignition OFF it went down to 16PSI and remained there. My initial gut feeling was that this wasn't the problem but I proceeded regardless in checking the diaphragms. First I checked the Tracker Valve. This required to unbolt the Starboard Fuel Rail and a few Harness Connectors (All Fuel Injectors, Top Coil and Top Spark Plug Lead) I was then able to slide the rail out enough to remove the Tracker Valve housing and to check the Diaphragm. This was in pretty good condition considering its age and certainly it did not have any problems. I then proceeded in reassembling everything back. I then repeated the same process to the port Rail and also found that the Fuel Regulator Diaphragm was fine. I will mention at this stage that although I have the special tool required to disassemble the older Air Pressure Regulator with a Diaphragm, in order to check replace the Tracker Valve or Fuel Regulator, I did not use any special tools. Just took my time and proceeded carefully. My engines have the post 2001 new Style Air Pressure Regulator which does not use the Diaphragm and I did not know how to check this, so I just left it. I reassembled everything again.
2) The second item on my agenda was to check the ECM for an issue outlined in the Mercury Bulletin 2001-02 (attached). During my search for the possible cause of my problem this was the only reference I could find from Mercury about a specific high idle speed. I again checked this as per the bulletin instructions and I also compared the test with the other engine. This also ended with a negative result.
3) Lastly I hooked up my DDT to the good engine and went to the Data Monitor section where I checked the TPI % reading. This was on 0. When I did the same on the faulty engine I noticed that the reading was 1.7%. I proceeded in readjusting my Throttle in Gear to Full Reverse and Full Forward then back to neutral. Rechecked the value and it was still 1.7%. I also noticed that the Idle Stop Screw on the Throttle Lever wasn't touching the stop, as I was able to manually push it back further. So I proceeded to readjust everything so that after a few Full Reverse and Forward the Idle Stop screw was always resting correctly on the Stop and the TPI % reading was reliably on 0.
At this point I crossed my fingers and attempted to fire the engine, obviously after having placed the ear muffs and water on! To my delight the engine idled perfectly.
The all job was completed in just under 2 hours and I am now very happy not only to have a perfectly working Optimax again at $0 cost, but also to have the peace of mind to know that the diaphragms on that engine are in good conditions.
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