Do Boats Vapor-lock?

[ddevore]

I've got a marine power 454 (the 330) in an enclosed compartment. It seems when I heat up the engine (a few laps around the lake, nothing major), then shut down and let the engine sit with the hatch closed I have a problem. When I fire up I have no problem, but when I get on it to head out it chokes, sometimes dies... If I leave the hatch up some there is no problem. Last weekend I swapped all the metal lines out with rubber to see if it would go away and it didn’t, I also replaced the fuel pump to try to fix it.
One thing I'm thinking may cause the problem is the fuel/w separator is before the pump - isn't it best to use the pump to push, not pull??
Any suggestions??

[xs ultra]

I had some what the same problem except I would get a very low fuel which made the engine loose power. Pressure reading after running and getting hot under the hatch.was 2 lbs. If your engine set up is like mine where the electric fuel pump is mounted up high about the height of the dist. with the carter fuel pump this what cure the problem.
I replaced the pump with a holley electric(motor did not have a spot a mech.pump)and mounted the pump on the transit down by the floor.The key factor I think was to have the pump located low. I think the carter would have also worked but the holley looked better.I used the 14lbs holley with a pressure reg. Pressure stays at 7lb hot or cold. runs good any time now.
Good luck!

[SmokinLowriderSS]

I've heard of it happening to some 4.3L V-6 I/O's on other boards (Trailerboats & BABC) so it can happen. As above, find out what that fuel pressure is, could be leaking back, but from the sound of it, it's heat if it goes away with the hood open. If you do have an Elec fuel pump mounted high, they don't suck very well, are made to push and it needs to be lower in some manner, fuel tank level. I think I'd want the separator ahead of the fuel pump myself to keep from geting water run thru it.

[MESA BALANCING]

Yes it does what I've done to the racing engines we've built is modified the water strainer and ran the fuel through it to cool the fuel for long sustained periods.

[Sleek-Jet]

I'm pretty sure that's the problem I'm having with my boat. I've got a 454 under a dog house hatch. If I idle for any length of time, the boat will burp, fart, and die when I go to get on the gas. Let it sit for a couple minutes and then all is good again.
I'm replacing the electric pump with a mechanicle next weekend. Same reason's as stated before, it'll be lower and below a lot of the heat in the compartment.

[502 JET]

I'm pretty sure that's the problem I'm having with my boat. I've got a 454 under a dog house hatch. If I idle for any length of time, the boat will burp, fart, and die when I go to get on the gas. Let it sit for a couple minutes and then all is good again.
I'm replacing the electric pump with a mechanicle next weekend. Same reason's as stated before, it'll be lower and below a lot of the heat in the compartment.
Before you go replacing parts check the fuel pressure to see if that is the problem.If your fuel pressure is good when you are having the problem take a look at the coil it can heat up and break down and give the same symptoms.The boat will run great until it heats up then let it cool off and it will run fine.

[Sleek-Jet]

As far as I can tell, the FP is falling off... The ignition system is next on the to-do list if that doesn't help. There's quite a bit more to this story than what I posted.
Regardless, I'm ash canning the electric pump. Never been a big fan of them anyways.

[ddevore]

The fuel pump is mounted right behind the dist and the top of the fuel pump is about the same level as the bottom of the distributor - the fuel tanks are mounted on each side of the boat and would have to be about the same height as the motor... I'll check the fuel pressure next time I can get it hot. Anyone think just moving the fuel/water seperator after the pump instead of before it would help?
It's that carter 7psi pump (brand new) though.

[DEEWAYNE]

Mercury offers a type of boost pump specifically for vapor locking probs. It mounts (usually) down low and closer to the orig. fuel pump. There are many service bulletins on this problem. The engines with the most problems are the ones with the "cool fuel" system. The best thing to do is try a higher grade fuel, if you have not done so already. This can minimize the fuels ability to sit and boil (vaporize/evaporate) in the fuel system. Another way is to idle the engine in neutral for 1-3 minutes before you shut your motor down AND run the blower at the same time to try and cool your compartment down.

[Nucking futs]

Just another Idea and it was happening to me, the fuel tanks are not venting. Sometimes it acted just like what you are describing and I changed fuel pumps,filters ect.Then it did it again and just for some odd reason i unscrewed the fuel cap on the tank next to me and it exhausted like it was presurized. Turned out thew fuel caps were not venting and the vent on the tanks were not working right. All is great now.
Tim