vapor lock
 

any one having vapor lock problems in a 7.4 merc

Fuel-injected or carb ?

Ethanol-based fuel being used or not ?

A carb engine usually has enough fuel in the bowl to restart again. Fuel-injected engines without water-cooled fuel rails WILL have the problem. (Ethanol boils at 87 deg F)

I was experiencing vapor lock on my Merc 5.7 fuel-injected engines because of using Ethanol fuels. Switched to non-Ethanol fuels and problem went away.

Yep, happened a few weeks ago to my friend's 7.4. It was a 100 degree day, took us a while to figure out it was vapor lock. After the first time, we let it idle a while before shutting down and open the hatch a bit when stopped. No more problems :drink:

fuel injected twin 7.4's but only having trouble with the portside motor

push the throttles all the way fwd. then turn the key on and off 3-4 times. then, with the key in the off position, pull the throttles all the way back, to normal position, turn the key one more time, wait for the fuel to prime and then hit start. if it begins to girgle, give it appx. 1/3 throttle and watch it... it should catch fairly quickly - then pull the throttles back to idle position and you should be good.

this works 100% of the time on the 525's, 600's and 700's. It's a bit trickier on the 850's & 1075's, but does work w/ them also... and is much easier than pulling out the wrenches and releasing the pressure lock in the line.

Hope that helps.

PS: and yes, letting it idle before shutting down certainly helps.

this seems to be happening to me with 500 EFI's. Only on the port motor...is there a fix?

mine was having this same problem, it was about 105 out and like what was said letting it idle before shutting it down really helps.