Mercury 700 vapor lock problems
 

My 2007 Mercury 700's have vapor lock issues. It has gone from bad to worse. The other day it vapor locked just idling in a no wake zone and would not start till the next day. Anyone have thoughts on this. It was 102 degree outside when this happen but it happened when it was running. Both engine are having the same problem now. What's up with this Andy Smith

What gas are you using...
 

...and are the fuel lines metal or rubber?

had this same problem on my 42 w/ 700s. only seemed to happen on extremely hot days. ran the blower and opened the hatches as soon as i slowed down to idle and while parked. not sure but it seemed to help the problem a bit. good luck.

Don't know if the 700's have the fuel pressure schrader valve on the motor, mines on the front of my 502 MPI. Not sure where on a SCI. In a pinch you can have someone turn the key to on a few times while relieving pressure. It will start and will get you home.

Easy fix, re-flash ECU and run non ethanol 89 octane you'll never have the problem again. Mercury did this from the factory stating in 2010. I have 2011 700's ran 92 with ethanol engines would not start in heat. Started running 89 non ethanol a year ago never had another problem. The re-flash will cost you approximately 10hp or so.

run your fuel return lines back to the fuel tank.. not the filter head. that seems to fix the problem.

I haven't had any problems with mine, even at 108 temps. They have Whipple upgrades.

I had (and probably still have) this same problem. Triple 700's and all three were hard to start after a run. Very frustrating and embarrassing. I posted and got a lot of good recommendations. One recommendation was to leave the hatch open after the run. Since this was easy, I tried it the very next day. Although it made a difference, the engines were still difficult to start. I have mechanical fuel pressure gauges and also the race view. I was concerned that the fuel regulators were not holding good pressure during cranking. I replaced the fuel regulators and that made a big difference, but the engines are still somewhat hard to start. The other recommendations that I received were more involved. I stumbled on 39 Unlimited’s post when he was experiencing problems. I talked with him and I am convinced that the re-flash is a good way to fix this. It will also help me because then I will be able to use 89 gas. At that time, the winter run season was about over so I have not done this yet and I have the donzi is in for an extensive refit. I will probably try to get this done by the fall season.

I have the 600. It is hard to start when hot. I found that cycling the key switch to the on position then off 3 times does the trick. No more problems.

Running fuel with no ethanol makes a major difference in starting all kinds of engines in hot weather. Get rid of the ethanol crap and only use non ethanol fuel in your boat. I bet that simple step will cure your problem and will be quick, easy and cheap to try. Check puregas.org to find non ethanol 93 octane fuel near you.