Optimax seems starved for fuel

[berudd]

So, while fishing a few weeks ago the motor died when we came off plane a back to idle. Gave nor horns or indications it was sick while running or through a no-wake zone a few minutes before. It would fire we we cranked and just stumble for a second and die. Tow back to ramp. Went out next day to fish on TM and tried it for kicks and it would stumble a bit longer but die and won't run. The next day, went out on the TM again and tried it again. Was able to get it running long enough to go about half a mile but died again. At this point I stopped trying due to fear of doing further damage.

Took it to a local, well respected shop and they are thus far stumped. They can get it run if the squirt carb cleaner in it and it will show good pressure on the compressor (~90psi) and with the fuel system (~80psi). The opened up the vapor canister and it was clean but they replaced the fuel filter and my old grey fuel lines with new stuff with no change. They had a working engine on hand so they swapped out its vapor canister and both fuel pumps with no luck. They also swapped out the computers. My was not showing any 'hard codes'. It didn't help my motor and the other motor ran fine on my computer.

At this point they are somewhat at a loss. Perhaps it is a sensor of some sort or a diaphragm that's not holding pressure in the fuel rail? They are continuing to work on it but I wanted to see if anyone here might have some similar experience that will shed light on this.

Also, this is the same engine from the following thread where I seem to have a bad alternator: http://www.bbcboards.net/showthread.php?t=802998

[DrewFlu33]

Have they not rebuilt the pulse fuel pump yet? That would've been the first thing I would've done after replacing the fuel lines. It's a cheap and easy job, and that's sure what it sounds like the problem is to me. That's exactly the symptom I had in my XRi EFI when one of the diaphragms from a cheap Sierra rebuild kit blew apart. I'm also no expert on Optimaxes, but have read (from admittedly questionable sources) that the compressor can build up fuel pressure and mask issues like a bad diaphragm that would be easy to diagnose on an EFI or carbed motor.

Surely they have rebuilt the pump already - I'm far from a marine mechanic, let alone one at a respected shop.

Also, before anyone says it (I was just about to....), his serial is in his signature!

Good luck solving the issue!

[berudd]

Well, they swapped out the two pumps associated with the vapor canister. Are you referring to a different pump? On their recommendation I've taken it to a different shop with a guy they felt was more qualified. He mentioned a possibility of a regulator in the fuel rail? He may be looking in the direction you mention. He didn't seem to think it would be hard to fix. We shall see. Thanks for the input.

[DrewFlu33]

I guess I'm not sure what pumps those would be. I've not looked at a 150, but on a 225, if you follow the fuel line into the tank, it's the box-shaped pump that the fuel line runs into first. The compressor is above it.

[berudd]

That sounds like one of the pumps they swapped out with the known good unit with no success.

[EuropeanAM]

I would make absolutely certain you get ALL of your pumps, and ESPECIALLY your PCM back. By back... I mean "back on your engine".

Need to test the basics PROPERLY:

-Compression Test

-Spark Test (Including condition of spark plugs, or better yet- a fresh set, properly gapped)

-Fuel QUALITY, Delivery, and Air/Fuel Pressure Tests **

** Air/Fuel Pressures should be read on a Liquid or Glycerin-Filled DUAL pressure gauge set. Record results for:

-IDLE (or CRANKING at 3-4 SECONDS IF ENGINE WILL NOT IDLE)
-Under Acceleration

-5/10/15 Seconds after engine shutdown.

Note:

Air/Fuel pressures you mentioned will NOT permit the engine to run. Fuel pressure MUST be higher than air pressure.

[berudd]

To close the loop Angler's Choice in Martinsville VA fixed me up. They found two things. First, a hose to the compressor had rub against a pulley long enough to wear a hole in it. This prevent it from holding enough pressure to run. I suspect this was the root cause of my shut down and failure to run. This was most likely caused by me when I replaced the fuseable link several weeks ago. Just seem to coincidental not to be. That hurts my pride a little but that is better than feeling like I've got an 8 year old engine that might be showing signs of coming apart on me. He also found that a diaphragm in the fuel rail was deformed and he replaced that as well. I'm not sure that this prevented the engine from running but I did notice that an occassional stumble I would notice at idle is now gone. It also seemed to start a little easier. Thankful to have my boat back and running well.

[Rangr90]

I have a Mercury 150 OptiMax 04' Serial# OT961046
My trouble is starting it will start and die out unless i put it it high idle to start and warm up then it will run fine.
Any answers?

Thanks
Rangr90

[SilverFox579]

I have a Mercury 150 OptiMax 04' Serial# OT961046
My trouble is starting it will start and die out unless i put it it high idle to start and warm up then it will run fine.
Any answers?

Thanks
Rangr90

Best to start a new topic for your engine but suspect you'll be advised to test diagnostics using the basics listed in reply #6.