2011 Mercury optimax pro xs

[Jwhit1704]

I am in need of some help. When I got my boat out for the first time this year it ran fine for most of the day and then it would stall and die at idle or low rpm's. I was able to get it started if I gave it a little throttle right away. I drained the gas that was in the tank, and changed the fuel filter. I put it on the hose and it ran fine after a few attempts. I thought I had the issue fixed until I took it out last Friday. Everything was good for most of the afternoon and it started doing it again, but this time it would not start up at all. I had to use the trolling motor to get back to the launch. I have since changed the plugs and checked for spark. I had spark. I have taken the vst apart and checked for blockage and put 12v to the high pressure pump and it worked. I have heard a lot of people talk about the rubber seal on the high pressure pump getting corroded but mine looked fine other than it being a little tapered. When I turn the key I can hear the pumps start. I did not mess with the pulse pump yet. It seems like a gas delivery issue. I found where the line from the primer bulb connected to the line from the motor had a small leak and I fixed that and still no start. I am no mechanic, but I do have common sense and would like to learn everything I can. I have not put guages on the shrader valves yet because I do not have a set. I did press the fuel one carefully and fuel came out. I have also noticed that when I prime the bulb and let it sit for a few minutes the bulb is not hard anymore. It's this normal? Any help would be appreciated. I just got the boat at the end of last year and have not even gotten the chance to really fish yet. Lol.

[EuropeanAM]

Please identify WHICH Optimax ProXS you have (preferably including the serial number). If over 130hp... it would go into a specific forum.

Welcome to BBC, BTW.

[Jwhit1704]

Thank you. I hope to learn as much as I can.
It is a 115 and the serial# 1B903362

[EuropeanAM]

Need to check the air and fuel pressures with a dual-pressure (glycerin-dampened) gauge set. Watch for air pressure not building or dumping off quickly (can be caused by reed-plate problem in compressor).

[Jwhit1704]

Well I was finally able to test the fuel and air pressure. At the vst shrader valve I am getting 30psi with the key turned on. On the fuel rail I am getting about 50psi for both air and fuel pressure while cranking the engine. I was not able to get a dual guage so I had to test them one at a time with guages from auto zone. I have since taken the belt loose and checked the air compressor and it seems fine. I have also checked the air and fuel diaphragms and they are both good. I have an appointment on Tuesday to take it in, but I was just wondering what you guys might think. Thank you.

[EuropeanAM]

Air pressure should build to approximately 94 psi within just a few revolutions of the flywheel.

Does it hold air pressure if you stop cranking?

Note: Tests done with non-dampened gauges are very limited in what information they provide.

[Jwhit1704]

It would drop down some and then hold at about 30psi. I took it in to a local retailer that services Mercury's in the area. I should hopefully get some info tomorrow. Thank you.

[EuropeanAM]

Working solely from the limited info provided, I'm going to say it may be a problem in the air compressor/reed plate.

[Jwhit1704]

So after the boat was looked at by the service guy he said everything looked good except I did have low pressure at the vst and it would not hold pressure. They told me that it would need to be rebuilt and that done of the parts are on backorder from mercury. I decided to take the boat home so I could look into it. I started taking the vst off to open it up and when I removed the return hose from the back of the vst I noticed what looked like a torn o ring. When I removed it, it is actually a seal. #888852
Could this have been causing all of my problems from the beginning? Thank you.

[EuropeanAM]

Possibly... I'd be checking the one inside the VST (seals the HP pump to the top cover) as well.

Still can't ignore that your air pressure is low.

[Jwhit1704]

Thank you for the response. I have the seal that you are talking about on order as well as the other one. They should be here by Thursday. The gentleman that looked at the motor said that everything checked out as good except the vst. I sure hope he is right, and the guages that I used from auto zone were just garbage. I just want to get out on the water. Lol. Thank you again for all of your help. This is all new to me, but I am happy to be learning what I can especially from someone as knowledgeable as you.