150 Optimax fuel issue

[GSP_Lures]

How are you doing, I have a 2007 Optimax 150 with 131.2 hours on it SN 1B472302. Last summer I was cruising around 20 mph then all of a sudden, my motor stalled like it ran out of gas. I could get it to fire back up, but if I gave it enough throttle to go on plane it would stall again. After limping it back to the docks I got the boat in my backyard and started it in a tub. The motor ran rough and would die after about 30 seconds. I pulled the fuel hose and realized that the liner was starting to separate so I replaced the hose, primer bulb, fuel separator, and the spark plugs.

This year I went to start the boat to get it ready for this season and it fired right up and ran for around 5 minutes before it started to stumble and catch back up and eventually stalled again. I started it again and the same thing would happen.

I have an appointment to get it looked at by a certified Optimax repair shop, but they cannot get me in until the end of May.

I have checked the fuel and air pressure, and they are within spec with a 10-psi difference, I am not getting any warning beeps or any codes from the merc monitor that I have installed. I am a pretty good auto mechanic but not very confident when working on outboards, I was going to pull the VST and see if maybe the screen on the pump was clogged with anything. Outside of the VST is there anything else that could cause the issues that I am having or any tests to troubleshoot my issue? I would prefer to get it fixed before June, if possible, any help would be greatly appreciated.

Thank You!

[SilverFox579]

I was going to pull the VST and see if maybe the screen on the pump was clogged with anything.

Screen is probably clogged with bits of liner, if you've never replaced the pulse pump, now would be a good time to do so.

[JOE54]

agree

[GSP_Lures]

Screen is probably clogged with bits of liner, if you've never replaced the pulse pump, now would be a good time to do so.

I appreciate it. I ordered the gasket for the VST and clamps for the hoses. I am hoping to have it cleaned out this weekend.

[GSP_Lures]

Should I replace the pulse pump or would buying the diaphragm kit and rebuilding it be worth it?

[SilverFox579]

Rebuild kit should be fine IMHO.

[leonreno]

Yep, just the diaphragm kit, the rest is just the housing, which I would imagine never really go bad. Not much to the whole pump, most rubber and plastic pieces inside two outer metal shells.

[EuropeanAM]

Should I replace the pulse pump or would buying the diaphragm kit and rebuilding it be worth it?

Rebuild kit. This is quite possibly the problem- and SHOULD HAVE BEEN DONE WHEN YOU REPLACED LINES, BULB AND FILTER. You've likely still got debris being distributed from A to B to D to (oh shoot... C was left out, there's debris in it and it's not working right, but wait, D and E now have debris again).....

This is why the FAQ Post "Fuel Lines & Performance Problems" is brutally honest and straightforward. You can easily ruin a whole season chasing something simple if it's not ALL done at the same time.

[GSP_Lures]

Thank you all for the replies I will order the rebuild kit and hopefully have this running before I give up and have a shop do it. Thank you

[JOE54]

[GSP_Lures]

Well most of my parts came in, I rebuilt the pulse pump, and cleaned the VST. It was a lot cleaner than I expected. I found corrosion around the pump inside the VST and the small seal that goes around the intake of the pump was really corroded and dry rotted. I am hoping that it was allowing air into the VST and causing my issues.

The small seal is supposed to come tomorrow hopefully early enough for me to get the motor back together and fired up.

I plan on cleaning the external tank I have and filling that with fresh fuel and the quicksilver fuel additives and fire it up off of that before feeding it with the boats fuel tank so I know that it isn’t a tank or fuel issue.

I appreciate all the help and I will keep you posted if the issue is solved

thank you

[lpugh]

If fuel / air pressures were correct while the motor stalled, this is not a fuel starvation issue, though I do agree that pump needs rebuild. He was not clear on what pressure were when this happened. Symptoms matches a pulse pump issue or air leak on suction side.

[GSP_Lures]

If fuel / air pressures were correct while the motor stalled, this is not a fuel starvation issue, though I do agree that pump needs rebuild. He was not clear on what pressure were when this happened. Symptoms matches a pulse pump issue or air leak on suction side.

I rebuilt the pulse pump and cleaned the VST and changed out the sleeve on the pump inside the VST. I verified that all the pumps were spinning when the VST was out also.

I hooked the motor up to an external tank to make sure fuel or the tank was not the issue and I still am having the same issue.

It stumbles for a half a second and then catches back up idles out normal for a minute then dies like the key was turned off. I tried to post a video but it was saying I did not have enough privileges.

Is there anything else I can check for that could be a quick fix before I end up taking it in to a shop?

Thank you

[GSP_Lures]

I ended up putting a clear hose on the pulse pump to make sure I was not getting any air once I got the hose filled there were no bubbles and still had stalling issues. I also pulled the end going to the VST to make sure that it was pumping fuel into the VST

I put the gauges on to see what it was reading (cheap harbor freight gauges) the fuel pressure went to 15 psi and 0 for air with key on. Once started the fuel jumped to 90 but was bouncing between 90 and 100 and air went to 80 and bounced between 75 and 85. When the motor stalled the gauges stopped on 80 for fuel and 70 for air. Unfortunately with harbor freight gauges I know they are not 100% accurate but none of the auto stores around me rent the liquid filled gauges.

Could this be something other than a fuel issue?

Thank you

[EuropeanAM]

Yes, it "could" be, but your readings are really not conclusive using that type of gauge.

[GSP_Lures]

Yes, it "could" be, but your readings are really not conclusive using that type of gauge.

I was doing some more research and when I relieved the pressure from the fuel pressure gauge I noticed a lot of bubbles instead of a steady stream of gas came out of the fuel rail. Would that be a symptom of a bad tracker valve or fuel regulator?

[JOE54]

no sir

[GSP_Lures]

I appreciate all of your help, unfortunately this is the first thing with a motor that has been able to defeat me. I’m going to take it in on the 13th and let the professionals with the proper diagnostic equipment take over. I don’t want to keep throwing money and parts at it when I don’t know for sure.

I will update this thread once they let me know, and again thank you for your time and help!