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Author Topic:   1999 Mercury OptiMax Trouble
grossjas posted 10-02-2011 03:26 PM ET (US)   Profile for grossjas   Send Email to grossjas  
My [1999 Mercury] OptiMax [later described as a 135-HP] is not starting properly. The check engine light comes on and [an aural alert sounder] beeps. Then [the 1999 Mercury OptiMax 135-HP] will not start at all. [The 1999 Mercury OptiMax 135-HP] fires, but does not stay running. I took in [the 1999 Mercury OptiMax 135-HP] to my local mechanic, and he said both [throttle position sensors] were bad. He hooked up [the 1999 Mercury OptiMax 135-HP] to [a proprietary Mercury digital diagnostic tool], and both sensors had [about] 75 faults. I had [the dealer] replace both [throttle position sensors]. [I] went to use the boat, and the exact same problem happened, [that is, the starting was improper, the check engine light came on, and an aural alert sounder began to beep]. I didn't make it off the boat launch. I am very frustrated, as I spent a lot of money to have this fixed and obviously they didn't fix the problem. Any suggestions? I live in Northern Michigan. Anybody know a good mechanic for the OptiMax in Northern Michigan?
jimh posted 10-03-2011 07:40 AM ET (US)     Profile for jimh  Send Email to jimh     
Based on your narrative, it appears that the throttle position sensors were not the cause of the starting problem, the sounding of the aural alert, or the illumination of the check engine lamp.

Usually the owner's manual for an outboard engine will have specific information describing the alarm system, and typically there will be suggestions for interpretation of the meaning of the alarm signals. Usually the cadence of the aural alarm is varied to impart different meanings. Also, the operating condition of the engine when the alarm occurs can be used to infer meaning to the alarm. Give the owner's manual a careful reading to see if it can offer any advice on interpretation of the alarm signal.

grossjas posted 10-03-2011 07:49 AM ET (US)     Profile for grossjas  Send Email to grossjas     
I'm sorry, it is a [1999] 135 OptiMax. It is hard to decipher the aural alert as it doesn't do it everytime. When it starts it beeps then the engine dies, then when trying to restart it fires but will not stay running. No alerts. By the wat the battery is an Optima blus top 1 year old has plenty of power.
jimh posted 10-03-2011 08:11 AM ET (US)     Profile for jimh  Send Email to jimh     
It was good that you mentioned the engine cranking battery, as insufficient voltage under load while cranking the Mercury OptiMax engine can be a cause of starting difficulty. Have you checked the voltage at the engine while cranking? Even if the battery is in perfect condition, the least little bit of resistance in the cables and connections between the battery and the engine can introduce voltage drop.
grossjas posted 10-03-2011 11:33 AM ET (US)     Profile for grossjas  Send Email to grossjas     
Just got back from the shop. [The technician] re-hooked-up the DDT. With the new TPI's the DDT showed [several] faults on each TPI. I told the technician that I think I had generated them by trying to start the engine with the idle advanced. He told me that will not generate a fault code. I think he is wrong.

I have both of the old TPI's in my hands. I stopped at a different Mercury dealer. They told me the only way to test them is when they are in the engine. Is this true? I would like to test the old TPI's to confirm that I believe they are good.

After inspecting the engine opposite side of the tracker valve or port side, the lower pressure valve appeared to have a gasoline-oil mixture leaking from it. The technician was going to check air and fuel pressures this afternoon.

Obviously the problem was misdiagnosed. Now we have to figure out what the real problem is and I now have to prove the TPI's were replaced unnecessarily at a hefty cost. Any help [with making a corret diagnosis of the problem] would be appreciated.

martyn1075 posted 10-03-2011 01:20 PM ET (US)     Profile for martyn1075  Send Email to martyn1075     
I feel for you, and I hate when this happens. The OptiMax is a highly technical engine, as are most modern engines--but specially the OptiMax. I would check both the fuel injectors and air injectorw. They were a constant problem on the first years. If anything is going wrong in that system, it could lead to other problems--maybe the problem you are encountering. I am not a technical guy. The theory is a little too much for me. But I know the injectors are sensitive, and the computer in your engine may be acting up due to a bad injector or two.--Martyn
captbone posted 10-03-2011 07:37 PM ET (US)     Profile for captbone  Send Email to captbone     
Advancing the throttle will throw the codes for TPS. The 1998 to 1999 series used the stacked TPS.

There is no oil mixture in the rails. The air pressure should be 80-PSI and the fuel should be 90-PSI. The fuel injectors rarely fail but the direct injectors can be a [problem source].

The tracker valve regulates the 10-PSI difference, and can leak fuel into the air side in the rail.

There are people that sell the air and fuel regulators if they need to be replaced; the factory does not sell them separately.

You can [sell] the TPS's if the dealership won't take them back.

grossjas posted 10-03-2011 08:24 PM ET (US)     Profile for grossjas  Send Email to grossjas     
As I said, there seems to be something leaking from the lower regulator on the port side fuel rail. Since this part is not available from the factory, and getting it from a third party is very expensive, I want to make sure it's the problem. If the gauges are reading the proper pressures can I assume the diaphragms are OK? From the outside the tracker valve looks OK. Is it alright to open it up to inspect?
captbone posted 10-03-2011 08:32 PM ET (US)     Profile for captbone  Send Email to captbone     
Do not open up the air or fuel pressure regulator. You can open up the tracker valve and check it out, but be sure which one you are opening.

If you have fuel on the air side, then replace the tracker valve, as they are cheap enough.

If you have correct air-fuel pressure then your regulators should be fine. You can check the compressor by pinching off the air dump line and it should spike the air pressure.

grossjas posted 10-03-2011 10:08 PM ET (US)     Profile for grossjas  Send Email to grossjas     
The tracker valve is the single one on the starboard side? it looks like it is removed with 4 Allen-head bolts.
captbone posted 10-03-2011 10:52 PM ET (US)     Profile for captbone  Send Email to captbone     
Off the top of my head, yes. It should be higher on the inside of the starboard rail, but triple check.
grossjas posted 10-06-2011 05:02 PM ET (US)     Profile for grossjas  Send Email to grossjas     
New diagnosis is the diaphram for the fuel regulator on the fuel rail is bad. I know I can buy one from a third party. I would love to hear some stories of people who had this problem, symtoms, how the new part worked, any advice on the regulator would be helpful.
captbone posted 10-06-2011 05:27 PM ET (US)     Profile for captbone  Send Email to captbone     
You need 80-PSI on air and 90-PSI on fuel. These regulators keep them within these specs.

Currently they only sell the complete rail with these in them due to EPA rules or something. They look very similar to the tracker valve diaphram. The reason that I said dont take them apart is because they have 80 to 90 pound springs that are a pain to reinstall without making a jig. The diaphram in these is the problem as they will tear or breakdown over time. Search online and find the correct diaphram and make the jig to replace them. It not expensive or really hard to do but instead is a pain.

jimh posted 10-08-2011 08:38 AM ET (US)     Profile for jimh  Send Email to jimh     
grossjac--Please do not create a new thread for every new question you have about the diagnosis and repair of your engine. You now have three threads on this topic. I have closed off the other two threads. Use this thread to continue the discussion of your engine repair.
grossjas posted 10-11-2011 06:20 PM ET (US)     Profile for grossjas  Send Email to grossjas     
Does the Mercury [digital diagnostic tool] give information on the operation of the throttle position sensors, that is, specifications and voltage running through it?
ukuslayer posted 10-13-2011 08:50 PM ET (US)     Profile for ukuslayer  Send Email to ukuslayer     
Not sure if the DDT gives you the info you want but I know it can diagnose a bad TPS. I had to replace both of mine on a 1999 225 Optimax. The only way I knew for sure was when the mechanic hooked up the DDT and was able to pinpoint the problem. I would think you should be able to tell if they are working properly also.

Please follow up on this problem as I am interested to here the outcome. I am having a similar hard start on my engine and am leaning towards the tracker valve being the problem.

grossjas posted 10-13-2011 09:48 PM ET (US)     Profile for grossjas  Send Email to grossjas     
It looks like the first diagnosis of bad TPS sensors was incorrect. The problem seems to be low fuel pressure, fuel pump checks out, fuel pressure [is about 70 to 75-PSI], leading me to believe there is a bad fuel [diaphragm in the fuel pressure regulator]. This leaves me between a rock and a hard place, as [the fuel pressure regulator is] not available for purchase except if you buy the complete rail. SOSMERC has said a tracker valve diaphragm can work for a fuel [pressure regulator] diaphragm?. Any further help would be much appreciated.
ukuslayer posted 10-14-2011 12:37 AM ET (US)     Profile for ukuslayer  Send Email to ukuslayer     
You can also buy the fuel diaphragm at I also saw them from the same company on eBay if you search Mercury Optimax. They are $350-each, kind of steep but considered to buying a whole fuel rail they are cheap if that is the only problem. Hope this helps and look forward to hearing if you resolve this problem.
grossjas posted 10-14-2011 07:38 AM ET (US)     Profile for grossjas  Send Email to grossjas     
I have seen them on the internet as well and I think that is a good option. I am just a little nervous due to knowing nothing about them and never hearing anyone's personal experience. If I were to replace the fuel [pressure regulator] I think I would also replace the air [pressure regulator], bringing the price to $700-- a lot of money without much knowledge of the actual product.
ukuslayer posted 10-16-2011 04:35 AM ET (US)     Profile for ukuslayer  Send Email to ukuslayer     
I agree, I would like to hear of a first hand account of someone dealing with them and how there product worked out as it is a lot money. Hope it works out for you.Aloha--Sean
grossjas posted 04-18-2012 08:01 AM ET (US)     Profile for grossjas  Send Email to grossjas     
Well its spring here in northern Michigan and I tackled a long awaited engine issue. As I had suspected the air pressure regulator diaphram was torn. I bought a used fuel rail and swaped them out. Problem immediatly fixed. Thanks CW again for all the help. At the same time I also replaced the thermastats, water pump, and poppet valve. This had been a saltwater engine before I bought it, sure glad I replaced those parts, t-stat stuck open, bad poppet valve diaphram. Thanks again
domlynch posted 04-20-2012 08:47 PM ET (US)     Profile for domlynch    
If I had that much trouble with an engine, I would strongly consider a repower for peace of mind - especially if the rig is used in open waters.

No matter how much I had spent trying to get the old one going, even if it is going with new parts etc, I would still not feel at ease with it.

martyn1075 posted 04-20-2012 11:58 PM ET (US)     Profile for martyn1075  Send Email to martyn1075     
Its probably still cheaper just to fix it for now. I agree a newer engine would probably ease grossjas mind a bit but then you have to worry about paying it off over the years and at the end of the day it may be worth while to just attend to the problem until something major goes wrong. Thermostats are the norm with Optimax's even more so with the current models due to the Verado style lower end high speed pickups in the V6 3.0 models. Not sure if the smaller models offer that system.

Optimax Like: Expensive gas & Oil strong battery, proper maintenance (like any engine) and yes some luck on your side. The newer the model the less risk you have to worry about as they seem to be more intelligent, with particular bugs worked out from the past. When they are tuned up they are fabulous.


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