2013 Mercury 175 pro XS two-stroke intermittent problem when temperatures above 80.

2013 Mercury 175 pro XS two-stroke intermittent problem when temperatures above 80. I have a mercury 175 that I’ve been having problems with. It started acting up last fall when it was hot but started working fine when weather cooled off and ran good all winter and early spring. I had it to the shop twice last week and taking it again Next week. It will run great in morning but when temperatures get above 80 Degs out side. It will start to shutdown when running or idling, no alarms. It sounds like it running out of fuel. When it does shut down it is hard to start back and coughs spits and sputters. Primer bulb stays hard. If you give it gas it appears to clear sometimes and may die a few times but if you can run it and will shut down again. It seems if you can get it on plane and run it long enough and get air moving across motor and cool cover it will start Working. It’s alway 80 degrees and sunny or hotter outside and if you place hand on motor cover it hurts to leave hand on cover. If you park in shade and allow to cool, it starts working. With mechanic on boat it started acting up and after removing cover to connect laptop it only shut down once in 30 min. We had to place cover back on motor and it started shutting off again. Laptop did not show anything. They have rebuild first pump that pumps from tank and went through VDM? and replaced top gasket on high pressure fuel pump. Has anyone saw a similar issue?

thanks.

is it loosing fuel psi or spark at plugs ????? need to know

I will give update Tuesday.

Just a guess... Take an infrared thermometer with you, and when it's stalling and acting up, use it to check the OUTLET end of the low pressure fuel pump.

Temp greater than 110F indicates the pump may be failing.

Update:
Spent the afternoon at the lake with a mechanic working on my boat. It has to be above 80° and sunny, little wind outside for probably start happening. 3 times it did shut off than running any rpm. It will die, and is hard to start back if you don’t give it gas when starting. Sounds like it got too much air in fuel and air injection. When we pull cover off and hook up fuel pressure gauge and computer problem goes away. We even installed cover on motor with gauges coming under cover. It ran fine until we ducted taped opening to prevent any air from coming in motor. We got it to do it a couple of times with fuel gauge on it and starting up. Fuel pressure would run 100-110 when motor was cool but when it would get hot. By hot I referring to air temp going in air intake above 147 deg F as hot. Fuel pressure gauge would start going between 90-120 really fast. After a mile run at 4500 rpm and then shutting down and waiting 10 minutes is when we would see air temp inside motor on laptop go above 147-152 and problem would show up start or idling it would shutting off motor and then hard to start. Fuel pressure would be 100-110 after key turned on and fuel pump ran for 3 seconds before key was turned to start. If you got boat on plane and cooled motor or parked in shade, got in wind, removed cover. Problem would go away and run fine.


Boat mechanic suspects, diaphragms, or possibly master relay.
We probably started it 100 times in the four hours working on it and two times when the boat switch was turned on, the fuel pump did not come on and pump the fuel up on the high pressure rail.


If you were on plane going above 45 mph and it shut off and keep throttle the same it will turn off for 2-4 seconds and then start back before it comes off plane and keeps going.


He was going to check on parts and replace diaphragm’s first.


Any suggestions ?

should be a constant 109 psi or very close to it.
Need know air pressure at the exact same time, 14.2 psi difference between air and fuel.

I did have tracker valve recently with very similar symptoms, took while to catch in the act, first look at tracker valve did not see the problem with it. What was odd was that it had no leak down at all most of time. Setting down watching the fuel pressure gauge and thinking this thru the pressure suddenly dropped 15 psi in about 10 seconds then held with no drop. pulled tracker valve back out and used a magnifier for inspection, sure enough found a very small hole in one side of it.

Quote:

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Originally Posted by EuropeanAM

Just a guess... Take an infrared thermometer with you, and when it's stalling and acting up, use it to check the OUTLET end of the low pressure fuel pump.

Temp greater than 110F indicates the pump may be failing.

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was this test done as requested ????

what was fuel psi at rail when it died 3 times and would not start , internal rail problem is not likely due to heat temps

No this test was not done. “Just a guess... Take an infrared thermometer with you, and when it's stalling and acting up, use it to check the OUTLET end of the low pressure fuel pump.” When we would remove cover, motor would start operating normally.

the pressure at the high rail was erratic and showed 90-120 PSI when it died 3 times. The weird thing is if motor was hot, fuel reading would be erratic 90-120 idling at low RPMs. Water pressure would be 3-5 on boat gauge but motor was peeing. But if I increase RPM and motor cooled down with water pressure going above 15 psi at 2500 rpm , fuel rail pressure would stabilize at 100-110. We saw this several times.

almost sounds as though fuel is vaporizing in rail from lack of water flow through rail i would think it should drop more than that

Quote:

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Originally Posted by JOE54

almost sounds as though fuel is vaporizing in rail from lack of water flow through rail i would think it should drop more than that

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Sounds like vapor lock plain and simple.
My 150 does this exact same thing once the air temps get into the 80's and I make long runs in the afternoon like this past Sunday. It's beyond frustrating.

Quote:

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Originally Posted by RattleHeadBaits

No this test was not done. “Just a guess... Take an infrared thermometer with you, and when it's stalling and acting up, use it to check the OUTLET end of the low pressure fuel pump.” When we would remove cover, motor would start operating normally.

.

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Make sure you check the idle relief boot. If it's leaking even slightly it can cause "instantly works fine with cowling removed".

Same for any other exhaust leak.

agree ^^^^

Update. After spending an afternoon on lake with mechanic and not finding the problem, we called it a day. It did shut off a couple of times, rough running after restart then clear up. Internal temp from his laptop but always read above 150° F, When the problem would show up. That day on the way home boat was empty, I filled up boat with 100% gas and motor has not shut off since. I have run 3 tanks of 100% gas in temps above 80 degrees and it has not acted up once. The only thing I can figure is gas with ethanol is vaporizing in the rail under certain conditions. I’ll just continue to run 100% gas.

Thanks. RHB.

:smile: vapor loc plain and simple :nanner:junky fuel can be a killer , if your in the south might try new waterpump and use 120 degree thermostats will drop temp on it some

Quote:

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Originally Posted by RattleHeadBaits

No this test was not done. “Just a guess... Take an infrared thermometer with you, and when it's stalling and acting up, use it to check the OUTLET end of the low pressure fuel pump.” When we would remove cover, motor would start operating normally.

the pressure at the high rail was erratic and showed 90-120 PSI when it died 3 times. The weird thing is if motor was hot, fuel reading would be erratic 90-120 idling at low RPMs. Water pressure would be 3-5 on boat gauge but motor was peeing. But if I increase RPM and motor cooled down with water pressure going above 15 psi at 2500 rpm , fuel rail pressure would stabilize at 100-110. We saw this several times.

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Take the temps as Don recommended.
That is not stabilized by any means air 95 fuel 109 +or- 2 max
Sounds like cavitation or vapor from one of the pumps to me!
Put another gauge on the vst low pressure port and take a video of all three and post a link to it,

Update

I have been running 100% gas in it for the last year and it has not shut off any with 100% gas. I fish 1-3 times a week and have filled it up 12 tanks with 100% gas. In Oct. after outside temp got down to freezing, I filled up with a tank of Regular gas with ethanol. I use this gas station in my GMC truck and always run fine. While it was cool out side it ran fine. But when it got back in the 80 in November the motor started acting up. It was the same as before, on a long idle it would die. motor would start back and run rough for 10-30 seconds. if you get on plane any rpm, it would shut off and if going fast enough the fire back before coming off plane. It did this 8-9 time while fishing with air temp 80+. It always shut off after getting on plain in the first 2 min. If i could make a 3-4 mile run and get air moving over motor it would run fine. It would happen more when I would running and gunning fishing. If I fished more than 30 min before starting and did not make a long idle it would work fine. This was on 11-8-2024 with Ethanol gas i ran most gas out of boat and left lake and filled up with 100% gas and problem went away. Last year the shop rebuild pick up fuel pump and cleaned junk out of fuel rail and replaced water pump. With the weather cooling off, not sure I will get problem corrected until next year.

Thanks Dow

I am betting on one of these three items based on what i consider a very good symptom list, High pressure fuel pump, split boot that seals to hp pump to outlet or the hourglass shaped boot (fuel director) that goes on the fuel return line where it connects to the VST. The ethanol is just enough to push it over the edge causing vapor lock, the item I listed could cause fuel aeration being the root cause.