Vapor lock?

[Alaboat]

Just got boat out of the shop after having it there for a new long block, starter and exhaust manifolds. Long story but won't expound here. You can read all about it in another thread in the OMC section. Here's what I've got: reman VMC7 4.3 Vortec with 2 bbl carb with about 10 hours on break-in. was out on the lake 2 days ago and had run for a while and stopped for a swim for about 45 minutes; air temp was near 100. When we got ready to leave, I started the engine with no problem and throttled up. As I was about to get on plane, the engine just died. Tried to restart it and it sounded like it was starving for fuel. Within minutes, somebody stopped and towed us in. Tried again at the launch and it wouldn't start so we loaded up and went home. About 3 hours later, I decided to pull the fuel filter/water separator and see what fuel looked like and check for water. Looked good so spun it back on and after a few attempts (should have filled filter back up before reinstalling), engine fired right up. Tried this several more times and fired right up again and again. Talked to mechanic next morning and he said he just about guarantees I experienced a vapor lock because of the following conditions:

High outside air temp
Engine had been run for 45+- minutes before shutting down without a few minutes of idle cool down
Engine compartment had soaked in engine temp for that time with no ventilation
Use of Ethanol fuel which has a higher evaporation/ vapor rate
Engine vents are at back of boat at swim deck which doesn't promote good ventilation

Here were his recommendations in the future, run blower all the time when running when outside temperature is really hot, run at idle speed for 3-4 minutes after cruising before shutting down, when stopped, leave engine cover open to let hot air escape and engine cool down some.

My question after all this long-winded explanation is, are vapor locks common with my engine set-up and do you think this is what happened?

 

[alldodge]

It could be vapor lock but with a carb it is not as much an issue as with EFI. If the carb is vapor locked you should be able to pump the throttle to release vapor pressure and allow fuel to come in.

Agree, when its hot, come down to idle and idle for 4 to 5 minutes to allow engine to cool more. Running a blower will also help.

To find out if it is vapor lock, once it happens, remove flame arrestor and look down carb throat to see if fuel enters when throttle is pumped.

 

[Alaboat]

Spent some more time on the water this weekend and paid more attention to allowing for cool down and ran the blower more often. Also idled for several minutes each time before cutting engine. Didn't experience this problem again but did end up towing somebody for about an hour back to the launch. Need about 6 more hours on engine break in. At least if I ever experience the "vapor lock" again, I will have a few things to consider to help remedy the problem. Thanks Alldodge!