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Author Topic:   2004 Mercury OptiMax 175 Low RPM Failure

bkoelbel posted 08-20-2012 09:38 AM ET (US)
On a recent trip from Dover NH to Kittery Point, Maine my exceptionally reliable 175-HP OptiMax started stalling when engine speed dropped below 1,000-RPM. The OptiMax propels my 1986 Outrage 20. I decided to head back up river. [The 175-HP OptiMax] performed typically well over 1,300-RPM, only to have a few Maalox Moments while docking, as the motor repeatedly cut out. The 2004 engine has 570-well-maintained hours, has never pulled a skier, and is as pampered as a 570-hour machine can be. Good gas, diligent with StarTron. Before taking to a shop, any ideas where to start the analysis process?
Thanks

sosmerc posted 08-20-2012 10:52 AM ET (US)
I am assuming that you get no warning horn or warning messages on your Smartcraft Guage? I'd be looking at the tracker valve. It balances air and fuel pressure at low RPM. You also have a separate air and fuel pressure regulator, and one of them could also be going bad. If you have access to a pressure guage that attaches to Schrader valves, there are two valves that you can tap into on the fuel rails for checking air and fuel pressure. Mercury makes a neat dual pressure guage so you can monitor both at the same time. There should always be 10-PSI more fuel pressure than air pressure. Air pressure should be at least 80-PSI.
The Smartcraft system has no way to monitor pressure, so if something is wrong, such as a bad sparkplug or torn diaphragm, Smartcraft isn't going to tell you.
grossjas posted 08-20-2012 03:43 PM ET (US)
I had the same problem with my 135 Optimax at the end of last season. The problem started off as you described and eventuaully got to the point where the OptiMax would no longer run at all. It turned out to be what sosmerc explains. Mine was the fuel regulator diaphram. It is a part you cannot buy. I ended up buying a used fuel rail with the regulators still installed. A hint you may look for is these regulator caps have weep holes on them. Look for any oily a gas like discharge coming from them. Good luck!
bkoelbel posted 08-21-2012 06:54 AM ET (US)
Correct sasmerc: no warning signals at all. Thanks for the feedback gents. I am waiting the call from my mechanic--ugh.
jimh posted 08-21-2012 08:04 AM ET (US)
Why can't you buy the replacement part?
We have three comments: one say the fuel pressure regulator failed on his OptiMax; another says the problem may be the fuel pressure regulator; and a third described symptoms of a failed fuel pressure regulator. How does one service the fuel pressure regulator if it has failed? Is it a component of a larger assembly?
sosmerc posted 08-21-2012 04:46 PM ET (US)
Jimh, the tracker valve (which is basically a "regulator" whose mission is to balance out the "bumps" of the air compressor at lower rpm) can be serviced by replacing the diaphragm. However, the two other regulators, one for fuel and one for air, have to be replaced as part of the fuel rail assembly. This makes it pretty expensive and seems a bit extreme......but I believe the reason has to do with EPA emissions certification of the fuel rails and they are tested as "an assembly". Mercury simply is not allowed to sell these regulators individually nor do they offer the internal parts for them individually.
It would be interesting to know what liability a shop might expose themselves to if they install say a used regulator off of some other exact same model engine. I have never seen or read anything to sugguest that the EPA or any other authorities are "testing" outboards at the boat ramp to see if they are in compliance with emission rules.
sosmerc posted 08-22-2012 01:57 PM ET (US)
I see now that one CAN purchase the air pressure regulator separately as well as the tracker valve parts. It's the fuel pressure regulator that can't be purchased seperately from the fuel rail.

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Author	Topic: 2004 Mercury OptiMax 175 Low RPM Failure
bkoelbel	posted 08-20-2012 09:38 AM ET (US) On a recent trip from Dover NH to Kittery Point, Maine my exceptionally reliable 175-HP OptiMax started stalling when engine speed dropped below 1,000-RPM. The OptiMax propels my 1986 Outrage 20. I decided to head back up river. [The 175-HP OptiMax] performed typically well over 1,300-RPM, only to have a few Maalox Moments while docking, as the motor repeatedly cut out. The 2004 engine has 570-well-maintained hours, has never pulled a skier, and is as pampered as a 570-hour machine can be. Good gas, diligent with StarTron. Before taking to a shop, any ideas where to start the analysis process? Thanks
sosmerc	posted 08-20-2012 10:52 AM ET (US) I am assuming that you get no warning horn or warning messages on your Smartcraft Guage? I'd be looking at the tracker valve. It balances air and fuel pressure at low RPM. You also have a separate air and fuel pressure regulator, and one of them could also be going bad. If you have access to a pressure guage that attaches to Schrader valves, there are two valves that you can tap into on the fuel rails for checking air and fuel pressure. Mercury makes a neat dual pressure guage so you can monitor both at the same time. There should always be 10-PSI more fuel pressure than air pressure. Air pressure should be at least 80-PSI. The Smartcraft system has no way to monitor pressure, so if something is wrong, such as a bad sparkplug or torn diaphragm, Smartcraft isn't going to tell you.
grossjas	posted 08-20-2012 03:43 PM ET (US) I had the same problem with my 135 Optimax at the end of last season. The problem started off as you described and eventuaully got to the point where the OptiMax would no longer run at all. It turned out to be what sosmerc explains. Mine was the fuel regulator diaphram. It is a part you cannot buy. I ended up buying a used fuel rail with the regulators still installed. A hint you may look for is these regulator caps have weep holes on them. Look for any oily a gas like discharge coming from them. Good luck!
bkoelbel	posted 08-21-2012 06:54 AM ET (US) Correct sasmerc: no warning signals at all. Thanks for the feedback gents. I am waiting the call from my mechanic--ugh.
jimh	posted 08-21-2012 08:04 AM ET (US) Why can't you buy the replacement part? We have three comments: one say the fuel pressure regulator failed on his OptiMax; another says the problem may be the fuel pressure regulator; and a third described symptoms of a failed fuel pressure regulator. How does one service the fuel pressure regulator if it has failed? Is it a component of a larger assembly?
sosmerc	posted 08-21-2012 04:46 PM ET (US) Jimh, the tracker valve (which is basically a "regulator" whose mission is to balance out the "bumps" of the air compressor at lower rpm) can be serviced by replacing the diaphragm. However, the two other regulators, one for fuel and one for air, have to be replaced as part of the fuel rail assembly. This makes it pretty expensive and seems a bit extreme......but I believe the reason has to do with EPA emissions certification of the fuel rails and they are tested as "an assembly". Mercury simply is not allowed to sell these regulators individually nor do they offer the internal parts for them individually. It would be interesting to know what liability a shop might expose themselves to if they install say a used regulator off of some other exact same model engine. I have never seen or read anything to sugguest that the EPA or any other authorities are "testing" outboards at the boat ramp to see if they are in compliance with emission rules.
sosmerc	posted 08-22-2012 01:57 PM ET (US) I see now that one CAN purchase the air pressure regulator separately as well as the tracker valve parts. It's the fuel pressure regulator that can't be purchased seperately from the fuel rail.