Vapor Lock, Replace Fuel Pump or add 2nd Low Pressure fuel pump?

[lowdrag]

I've had the vapor lock issue on my '06 21v since the first time I took it out brand new. I've now got a 2 year old and a 4 year old and this is the first year we've been able to start spending a lot of time on the boat as a family. I guess that's what made me realize this problem for what it is instead of an inconvenience. It's a safety issue. My boat was bad enough that it was a given that it would vapor lock if we let it sit for a half hour or more after running it. Nothing help, running the blower, leaving the cover open, etc. A lot of that is because all of the fuel available here is 10% ethanol and the lake we are usually on feeds a power plant so the water gets pretty warm. It hit me while we were anchored up and the kids were swimming. What happens if one of them gets hurt and I need to run back to dock in a hurry? The last thing I want to do is work on a vapor locked boat in that situation.

I finally just went ahead and bought the indmar secondary pump kit on skidim. Install isn't bad at all. It took me a couple of hours but most of that was figuring exactly how and where I wanted to mount it, not actually working. I mounted it right to the stringer on the port side just aft of the fuel tank. The biggest problem I had was space between the v drive and stringer. It's pretty much impossible to get a drill in there to start the holes for the mounting bracket. If you've got a drill that you can get an angle drive attachment for that would work. I've got a cordless impact driver which was just short enough to get the job done. The included bolts for mounting the bracket aren't ideal either. They are machine threaded so they're not made to hold well in fiberglass. I undersized the holes a little bit and they are working fine so far but I'll probably swap them out when I find some small lag bolts that are stainless or treated so they won't rust.

So far everything has worked great. Not a single problem since the install.

[LloydP]

Since I started using Marine Sta-Bil with every fill-up (after having to replace the fuel pump), I have had almost no vapor lock problems - in spite of the fact that it has been a really hot summer here.

[rtpaxton2]

I learned that the ethanol that they are putting in the fuel vaporizes and causes the vapor lock. Look for stations that use less ethanol in the fuel (if possible), add fuel stabilizers, and when you stop, open the engine compartment to vent it. One owner told me that he would soak a towel in the lake and wrap it around the fuel pump.

My boat had the second fuel pump added to it, and I don't have any problems (as of yet, knock on wood) with it vapor locking.

[ProZach415]

I have recently put the fuel pump through a heat soak period on a couple hot days and had no problems. I know this is a old issue from last summer but I just had a chance to really test my aplication on hot days. I relocated and replaced the exiting fuel pump and have had no problems since then using the cheapest gas I can find.

[CornRickey]

I would like to know how vapor lock (supposedly) is so prevalent in boats with fuel injection? I understand that the fuel possible could vaporize in the fuel line but with a electric pump. It should self prime quickly and clear up. No differently than running out of gas then putting gas in it. Cars would be on the side of the road all through the southern states. I don't get it.

[ProZach415]

I don't know how to answer your question… other than I know what fixes it. Someone on here probably will... I know how to fix this problem but cannot swear to what causes it other than a “heat soak” period. All I know is pouring cold water on an old fuel pump that has been through a "heat soak" period will resolve the issue immediately and get you going temporarily. Replacing the fuel pump totally resolves the issue permanently... until it wears out again I suppose. I guess the fuel pump just gets worn out over time and losses it suction power... Maybe ethanol wears the pump out faster, maybe not.

[CornRickey]

I'm thinking your right. It's not the traditional "vapor lock" you see with carbed engines but a heat seam issue with electric components.

[jdub667]

I had the same issue on my 07 21V so i went with a Bosch 044 fuel pump and mounted it next to the v-drive very little replumbing just the high psi line had one made at the parts store and no more issues. With the stock fuel pump mount on the motor it gets hotter than hell so I can see why everyone has issues.

[tg0824SSVGG]

Hmm - had this happen for the first time at Lake Powell last week 20 miles from NOWHERE ... the squirt gun cooling method stopped it, but I can't tell if
the pump is shot - it was an anomaly - had run hard at 30MPH for 1.5 hours in 105 temp, then sat for an hour -- then nothing until I "chilled" the pump a few times,
started and ran fine the rest of the week.

2008 240H Indmar Cat with the 2 fuel pumps to eliminate this problem, but it was HOT and I was pushing it hard.

[ProZach415]

Hmm - had this happen for the first time at Lake Powell last week 20 miles from NOWHERE ... the squirt gun cooling method stopped it, but I can't tell if
the pump is shot - it was an anomaly - had run hard at 30MPH for 1.5 hours in 105 temp, then sat for an hour -- then nothing until I "chilled" the pump a few times,
started and ran fine the rest of the week.

2008 240H Indmar Cat with the 2 fuel pumps to eliminate this problem, but it was HOT and I was pushing it hard.

You could run the boat all day in those temps as long as you dont stop and let the "heat soak" process take place. As long as you are running the motor it stays cool enough for everything to work. When you stop, the heat starts to radiate from the motor because the motor is no longer being cooled my the moving water.