2012 150 Optimax ProXS Help Please

[BrianMStevens]

First, thanks for letting me join. Hope to be able to maybe get some answers here since a few other sites not having much luck. Everybody get a beer. Will try to keep it short. Spring it ran great on muffs before we took it on fishing trip. When on trip launched and let warm up decent at dock. Pointed it out in the lake and it stumbled but took off and ran for 10 minutes 1/2 throttle or little more and it bogged and then stalled. Would start right back up but not respond to throttle. So came in on kicker. Bulb felt soft so tried new one next day. Again ran great on muffs but took to lake and same thing it would die after 10 minutes or so of running. Took to Marina and they put new head gasket on compressor and said 2 injectors were sticking open. They wanted to put all new injectors in so I took home. Removed all injectors and hacked checked, cleaned. Airs were dirtiest but all came back as excellent. Put together and ran at dock for half hour. She purred. Pointed into lake and immediately coughed/stalled. Wold start right back up but take no throttle. Would idle 2 minutes then die. Hit key start right back up and die 2 minutes later. And repeat. Home on muffs let run 15 minutes then it would die. Start back up and run for 30 seconds. And repeat. So next time I put gauges on it and air was 95, fuel 105 plus maybe 1 or 2 more needle bounced a little. So one question is gauges went to zero in 30 seconds after key off. Is one or both supposed to hold longer that when shut down? New filter was put on before trying on the lake after injectors put back in. So………I’m not afraid to take some stuff apart so where may be the next place I start to look? I know it could be diaphragms, maybe fuel pumps, maybe reeds? If I have to I will take it to a different shop but just trying to do a few things myself rather than someone else spending a lot of time trying to do the same thing. Thanks for anyones help

[25two.stroke]

I had a bad tps do the exact same thing. Check it with a ddt and engine off. Make sure the tps responds as you throttle up and down smoothly.

[half fast]

what color are the direct injectors ? what spark plugs are in it ? with it running does fuel come out of the air side if you dump a little off ? does it have old merc grey fuel line from fuel tank to the engine ? have you tried a diff fuel tank yet ? is there any water in the water sep fuel filter ? hf...

[David - WI]

Not much help, but it's not reeds if it runs good for even a few minutes. They are either good or bad... not intermittent.

If the fuel tank vent or vent line gets plugged then vacuum builds up in the tank and starves the motor for fuel... takes a while. Probably not it, but something to look at.

[BrianMStevens]

Thank you for your reply. Will see if I can get this checked out

[BrianMStevens]

Will have to see if I can get the TPS checked out. Thanks

[BrianMStevens]

Injectors are Red. Plugs will have to look. Will have to run it again and see if fuel comes out but don’t think so . Nothing came flying out or smelled like gas when I unhooked the gauge on the air. Fuel lines are good. Ran on 3 gallon tank first in the lake. Switched to main tank in middle of lake with no change. No water in filter. I pumped 2 gallons worth from main tank checking this before I even ran it again when I got it back together and fuel was very clean. This thing ran perfect when put away last fall and then decided to be a turd this spring

[pcrussell50]

Will have to see if I can get the TPS checked out. Thanks

If it works like a car TPS, you can check it yourself with an AVM and piercing probes. Probe between Vref and the other wire and the AVM needle should sweep smoothly without stopping or hanging up. Sorry not specific because I don’t know those motors well at all. Point being you probe the correct wires and with a healthy TPS, you should get a smooth needle sweep as you open and close the TPS.

Someone here can probably give you more specifics. I’m just trying to give you hope that you should be able to do this DIY. Similar to this youtube video testing another Opti TPS: https://youtu.be/kS6E2p8Uzug. It’s only a couple of minutes long, worth a watch.

-Peter

[half fast]

direct inj body is either blue , black or grey. If grey the spark plug should have a J in the model # and your air and fuel psi sounds close. If black or blue , 80 and 90 should be psi #'s .

[PanRonnie]

If those pressures are correct !?
I would suspect a partial clogged air pressure regulator giving higher than normal pressures

[25two.stroke]

If those pressures are correct !?
I would suspect a partial clogged air pressure regulator giving higher than normal pressures

I wouldn't worry about it. Its more likely his gauge is off. Bad regs usually cause more drastic changes in pressure. Usually, not always. But it will run on 95/105 just fine even if that is the true pressure. It wouldn't cause it to stall/not take gas.

[Jim Speros]

Nice call on pressures. Early optis ran 80 and 90 lbs. Pro XS run 90 and 105? Big ones anyway. Not sure what the specs are on 150 XS. Is that the manual you are referring too.

What I know is the regulators need special tools and replacement parts are limited. You, the owner of the boat, should be certain in your troubleshooting before you take them apart. I am understanding of your wish to fix it yourself but, There is nothing worse then rendering a running engine inoperable. Compounded by the nightmare of bringing an engine you disabled to a shop for assistance.

[PanRonnie]

Don't have the 150proxs manual but do have the 250
They do seem to be running higher pressures

[BrianMStevens]

Yes I know I need to get a service manual to help keep all of this in perspective. I do also believe that my motors pressures are where they need to be. I have some of this stuff saved in my favorites but I have saved so much stuff I have a lot to go through to find it. Prettier sure the tracker valve this has keeps it at the 15 pound difference too. These ProXS have a lot of Mercs Racing parts on them so it’s kind of a different animal compared to a regular Optimax. I’m feeling pretty strong that this is really fuel related so leaning towards trying to check the pumps out. May be something as simple as the screen on bottom of high pressure pump dirty or even the grommet on top of it dried and cracked or maybe the low pump is breaking down? Maybe the float in the VST is sticking? Won’t hurt I suppose to take the VST apart and check everything anyhow. Just trying to bend some peoples ears here these things have had to happen to someone else besides me and I do thank you all for trying to help me. Will get it figured out.

[Jim Speros]

Yes, I suggest you get the service manual for your engine before you take anything else apart. It will guide you thru troubleshooting. It also will explain theory. For example the tracker valve also acts like a shock absorber. Dampening and helps to stabilize pressures on either side of it. Manual will explain how the two regulators works and how to test them without dis assembling them.
The best thing you can do is troubleshoot systematically and not bounce around on assumptions.

[Jim Speros]

511609

That is only part of the pressure story. The air and fuel side each has a regulator. None are intended to be adjusted. My experience has shown
leaking diaphragms and pitted seats on the rail. A leaking tracker diaphragm will let fuel in the air side.

[BrianMStevens]

So one question I have is when the gauges were on it and the key was shut off it took 30 seconds for pressures to go back to zero. Is this normal or should it hold pressure for a given time

[Jim Speros]

I'm happier to see them hold. Fuel will leak down to 20 ish with engine off. Air should hold something.

[Jim Speros]

There are many places either can leak. The o rings in the gauges are notorious to leak as well. I've seen the pressure line from compressor to rail leak. Spray soapy water on external things.

[Jim Speros]

There are tests outlined in manual. On the air regulator you can pull dump hose from exhaust housing connection and listen to see if it is leaking down. There is a return fuel pressure hose to pinch to see if its leaking passed regulator.
Get the manual it will save you from chasing your tail and/ or creating un necessary work.

[David - WI]

Looks like the whole manual possibly?

https://www.manualslib.com/manual/824123/Mercury-Optimax-115.html#product-Optimax%20150

[BrianMStevens]

Some in here may pertain to my motor but more specific would be 150 Pro XS. 2012. Up I will see what I can find in this one that you sent. Thanks.

[BrianMStevens]

Thanks for trying but this is not the service manual that I ultimately need.