Vapor Lock
 

Vapor Lock...

So I had a new starter installed in the beginning of the season and the boat has fired up perfect all season… till this weekend. My trouble occurred after the boat had been warmed up and we will stop to hang out in a bay/pick up a boarder. During these situations I will turn off the motor. Once everyone is situated I will go to fire it back up and it will just crank and crank and crank. If I slip it into neutral and give it more throttle it will eventually fire up, but I have to kick it into gear to keep it alive. It will run perfect the rest of the evening with no issues. Sadly this again happened last night when we were out boarding. I called the shop and they said it sounded like a Vapor lock issue and for $324 they could sell me a new low pressure high volume fuel pump. Has anyone else had this experience/found a cheaper solution? (I have a 2001 direct drive Mastercraft)

Vlx
 

I had it happen two times in 4 years with my 2001 Malibu VLX. Same story, we had been running fine. We stopped for about 1 hour and it wouldn't start. I raised the engine cover, and waited about 15 minutes. It started and ran good after that. So two times in 4 years, I wasn't going to worry about it.

are you using fuel with ethanol in it?? if so this is your problem, while a new type of fuel pump "might" work, you might try a fuel additive. my houseboat on lake Powell has 2 westerbeke generators, one is vapor locking after about 1 hour of service, I'm not the only houseboat suffering from this problem, all marinas on Powell use ethanol in their fuel, in our case the fuel pump is next to the engine and once warmed up , the fuel will vaporize and shut the genset down. there are 50 houseboats up at bullfrog with this issue,at antelope point where I'm slipped almost all houseboats are suffering the same issue. if a fuel additive works for you it might get you through this season and you can address it in the winter...best of luck please report back as to what the outcome is.....

Vapor lock is caused by the fuel pump "pulling" fuel through a hot fuel line. This creates a lower pressure in the line and the fuel boils, aka vapor lock. The fix is to relocate the fuel pump to near the tank and "push" the fuel. j This creates a higher pressure in the fuel line. It's the reason most fuel pumps in cars are actually in the fuel tank.

Is it FI or carbuerated? If its carbuerated, install a $20 phenolic spacer (Summit or Jeggs) between the carb and manifold. Heat transfer can boil fuel in the carb and cause vapor lock. Some carbs are more susceptible than others though.

Wheelerwake is correct. It is how most 2014 brands have now been engineered and is the correct way. Most brands back in your model year refused to address the changes needed and came up with bandaid solutions that as our ethanhol% increase at the pump it rears its ugly head. The problem is that efi requires fuel pressures and if the excess pressure is not returned to the fuel tank it causes the fuel temp to rise as it gets comperssed over and over thus the vapor lock

Now to directly answer you question about cheaper way. Spend nothing and the next time it happens, simply reach in your cooler and pull out a bottle of cold water and pour directly on the fuel pump. The vapor will quickly condense and works 99% of the time. Seriously it really works.

i doubt that swapping fuel pumps will really help and i know it want fix the real problem. I cant imagine how much a shop would charge to modify a fuel tank not designed for return.

hey this happened to me at lake powell, it turned out to be the gas. it was high ethol...low cheap octain, so as the engine heated up / ran, it turned gas to vapor causing the vapor lock.. If you go get the green stable additive and add it into the gas it will clear the problem.

Moving the fuel pump closer to the tank fixed it for me.

Plus 1 !
This has worked for me everytime and that has been at least 4 or 5 times over the last few years.

You may be able to add a cheap heat shield depending on your setup. It may reduce the heat on the lines enough to get you by. Its probably happening because its much hotter outside and the fuel is a poor blend. You typically hear about this much more when people use the winter blend of fuel, such as the first few trips to the lake. Or just let it idle while picking someone up. If stopping to hang out, Ive read that opening up the compartments to cool the engine area off works, maybe turn the blower on for a bit.

I am assuming this is a 5.7 liter merc. I ran into the same problem with my 2000 Tige. I contacted Mercruiser, and they brought up the ethanol issue. Their tech was actually great to deal with. I used a fuel conditioner, but I continued to have intermittent vapor lock. Shortly after the vapor lock issue came up, the fuel pump crapped out completely. I replaced the pump then, as I had no choice, and I never had another problem. For what it's worth, I typically found that if I released the pressure at the valve on the fuel rail, the boat would fire right up. I'd always leave the cover open then to vent things.

I'm pretty sure Master Craft has never used Mercury...I know for a fact not in this era.