mercruiser vapor lock question

[Hot Rod Rooster]

hey people i am new here (first post) and i would like to ask a couple questions about my boat. i have a 95 malibu echelon with a 350 magnum multi port EFI. when it is hot outside and the boat has been running for a while and i shut it off for an extended period of time (more than half and hour) it will vapor lock on me. it will usually start but will die shortly after. the only way to get it started is to press the snifter valve on the end of the fuel rail and let it sit of a few minutes. once it starts it is good to go. if i leave the blower on or the motor cover up it' doesn't do it.

is there anything i can doto keep it form doing this again. i.e tighten up some fittings, change feul filters ect ect???

thanks in advance for your reply

Dallas Ostrom

[electricjohn]

Most of the inboard motor manufacturers had to develop some sort of add on kit to remedy the V.L. problems they had in the early years of marine EFI (early '90's). One remedy was as simple as useing an extra large fuel filter close to the motor. It was as big as an oil filter and twice as long.

[footnlongline]

Make sure the vent hose(should be under your dash and looks like a dryer hose. easy to knock off) is connected. unless you are motoring at idle, the vent hose should provide plenty of air circulation without the blower being on. Also make sure the vent(below the windshield) that it attaches to is not obstructed, My kids shoved a squishy ball in there once and I could barely see it.

[Hot Rod Rooster]

yes my vent hoses are hooked up and they work fine, i can feel the warm air coming out he back of the boat when we are moving. the problem arrises when i have the motor warmed right up (hard work for a period of time) and then i shut it off and leave it sit for half hour or better. if i leave the blower on or the motor cover up it doesn't do it but i hate leaving the cover up when it is sitiing there, i look like some knob wanting to show off his motor!LOL but i suppose it is better than having it vapor lock infront of a packed beach. i have this fancy fuel do dad above the mechanical fuel pump, i am assuming it might be some sort of a cooler/high pressure fuel pum but i am not sure it is like nothing i have seen on anything else.

did malibu ever come out with any kind of retro kit to "cure" the problem??? i know when it does it and how to make it not happen so i can live with it but i would rather cure it than live with it if oyu know what i mean!

thanks again

dallas

[Baddog]

If it is truly vapor locking you can try insulating your fuel lines and rails with standard 1/2" pipe insulation from Lowes. If it is acting like it is flooded, i.e. you get a lot of black smoke and gasy smell when you do get it restarted, it could be a bad engine temperature sensor telling the computer it is cold when in fact it is not and the conputer runs the engine too rich. A $20 part.

[Hot Rod Rooster]

i am pretty sure it is vapor lock as i don't recall ever seeing any black (feul rich) smoke coming from the back of the boat. if it were a bad temp sensor it would tend to start hard every time it was started hot wouldn't it? this boat starts like a champ ALL the time except when it has been let sit hot for an extended period of time.

when these engines vapor lock where exactly is it that the fuel getts boiling? rails, fuel line, fuel pumps, injectors?????

dallas

[Hot Rod Rooster]

see if this link to pics works

Edited August 26, 2007 by Hot Rod Rooster

[Hot Rod Rooster]

Edited August 26, 2007 by Hot Rod Rooster

[Hot Rod Rooster]

one other thing i was owndering about, i has seen 100's of other malibu engines and not one other one with this type intake manifold on it? is it some odd ball intake?

i looked in to the engine thing and mine is a 350 magnum EFI/MP tournament the others i have seen are just the efi. i take it the MP stands for micro precessor or something like that?

Edited August 27, 2007 by Hot Rod Rooster

[Hot Rod Rooster]

this is the boat it is in.

[Baddog]

Next time you ahve the vapor lock issue try dumping a can or two of lake water on your fuel rails and lines. If is vapor lock, the cooling water should condense the fuel vapor back to liquid and then start fine. If this is all true then try to insulate the fuel lines.

[Hot Rod Rooster]

i might just have to try that and see if it works. what would you insulate the lines with? is there anything that would look nice and not really out of place?

dallas

[footnlongline]

one other thing i was owndering about, i has seen 100's of other malibu engines and not one other one with this type intake manifold on it? is it some odd ball intake?

i looked in to the engine thing and mine is a 350 magnum EFI/MP tournament the others i have seen are just the efi. i take it the MP stands for micro precessor or something like that?

The MP stands for multi port which is a much more sophisticated fuel injection than throttle body which many boats have. That square thing you showed with the clear hoses on it are the vapor separating tank, if you see fuel in those clear hoses you should take it to a dealer.

[FlatBlackCJ]

I have a 02 VLX w the Monsoon engine and I have/had the same issues. I have spoken with Malibu, Indmar, local dealers, a certified MC/Malibu mechanic and all say they never heard of it nor SHOULD it happen w/ FI boats/or cars. I have told them to Google Malibu Vapor Lock and see all the "non-existent" vapor lock. I did all the things the boards have said: New fuel pump, fuel filter, bypass regulator, cycled key on and off several times, purges shrader valve on the fuel rail, insulated the lines and poured cold water on the pump. So far, the cold water works best. Well, I was not content with that so I decided to make up my own fuel system. The biggest challenge was plugging the hole in the end of the fuel rail where the fuel pressure regulator goes. I went to a local pull and pay junk yard and snagged two regulators off a Grand Prix and one off a Cavilier. Went home and cut off the plug portion and welded it to some flat bar and made my own filler plug. Then I added a 40 PSI fuel pump from MSD and a fuel pressure regulator w a return from Aeromotive and some fittings and braided high pressure lines from a local speed shop. Had to do some swapping of fittings to get 1/2 inch out of the fuel tank to the fuel pump, after all is said and done, it works great. We took it out this last week and after some fuel pressure adjustment, she runs likes crazy from idle to wide open. Let it sit for 30 minutes and she fired right up and I threw my spare water bottle in the trash.

This may not be USCG approved, but I have never seen an officer ask to see the engine compartment. Besides, it has all the high pressure stuff a race car would have, so I figure it is as safe or safer than what came in the boat to begin with.

[Dukester]

I have a 02 VLX w the Monsoon engine and I have/had the same issues. I have spoken with Malibu, Indmar, local dealers, a certified MC/Malibu mechanic and all say they never heard of it nor SHOULD it happen w/ FI boats/or cars. I have told them to Google Malibu Vapor Lock and see all the "non-existent" vapor lock. I did all the things the boards have said: New fuel pump, fuel filter, bypass regulator, cycled key on and off several times, purges shrader valve on the fuel rail, insulated the lines and poured cold water on the pump. So far, the cold water works best. Well, I was not content with that so I decided to make up my own fuel system. The biggest challenge was plugging the hole in the end of the fuel rail where the fuel pressure regulator goes. I went to a local pull and pay junk yard and snagged two regulators off a Grand Prix and one off a Cavilier. Went home and cut off the plug portion and welded it to some flat bar and made my own filler plug. Then I added a 40 PSI fuel pump from MSD and a fuel pressure regulator w a return from Aeromotive and some fittings and braided high pressure lines from a local speed shop. Had to do some swapping of fittings to get 1/2 inch out of the fuel tank to the fuel pump, after all is said and done, it works great. We took it out this last week and after some fuel pressure adjustment, she runs likes crazy from idle to wide open. Let it sit for 30 minutes and she fired right up and I threw my spare water bottle in the trash.

This may not be USCG approved, but I have never seen an officer ask to see the engine compartment. Besides, it has all the high pressure stuff a race car would have, so I figure it is as safe or safer than what came in the boat to begin with.

I have a 02 VLX w the Monsoon engine and I have/had the same issues. I have spoken with Malibu, Indmar, local dealers, a certified MC/Malibu mechanic and all say they never heard of it nor SHOULD it happen w/ FI boats/or cars. I have told them to Google Malibu Vapor Lock and see all the "non-existent" vapor lock. I did all the things the boards have said: New fuel pump, fuel filter, bypass regulator, cycled key on and off several times, purges shrader valve on the fuel rail, insulated the lines and poured cold water on the pump. So far, the cold water works best. Well, I was not content with that so I decided to make up my own fuel system. The biggest challenge was plugging the hole in the end of the fuel rail where the fuel pressure regulator goes. I went to a local pull and pay junk yard and snagged two regulators off a Grand Prix and one off a Cavilier. Went home and cut off the plug portion and welded it to some flat bar and made my own filler plug. Then I added a 40 PSI fuel pump from MSD and a fuel pressure regulator w a return from Aeromotive and some fittings and braided high pressure lines from a local speed shop. Had to do some swapping of fittings to get 1/2 inch out of the fuel tank to the fuel pump, after all is said and done, it works great. We took it out this last week and after some fuel pressure adjustment, she runs likes crazy from idle to wide open. Let it sit for 30 minutes and she fired right up and I threw my spare water bottle in the trash.

This may not be USCG approved, but I have never seen an officer ask to see the engine compartment. Besides, it has all the high pressure stuff a race car would have, so I figure it is as safe or safer than what came in the boat to begin with.

I have the same issue with my 95 Echelon , and have tried many remedies over the years with limited success. I have been considering replacing the fuel pump in a similar fashion to what you describe. Do you have any pics of that retrofit that you can share. Also, since the post is a few years old, did this solve the vapor lock issue?

[MadMan]

Vapor lock is caused by the fuel pump pulling fuel from the fuel tank through a hot fuel line. This suction causes the fuel to boil (it boils at a lower temp when it's at less then atmospheric pressure). This is vapor lock.

In later years it was prevented by installing the pump in the fuel tank. It was also fixed by installing a low pressure (~6 psi) fuel pump at the tank to pump fuel to the higher pressure pump. You could do this. Just install a marine carburetor fuel pump at the tank.

Edited July 26, 2015 by MadMan

[Vtxdave]

I had this happen all the time on my 07 moomba outback with inmar 350. I would put a to in the cooler and soak it with water and put the town on the fuel line and it would start up after the to sitting there for a few minutes. The only other thing I could do to prevent if from happening was run ethanol free fuel. With the ethanol free fuel it never did it

[toddthelineman]

Ethanol free never vapor locks for me either, and my boat vapor locks a lot.

To the original poster: a friend of mine has a similar intake on his 94, but it is a 454. He also has a mercruiser cool fuel system. Water cooled fuel lines, I believe

[TeamAllen]

Mercruiser makes a kit that uses a secondary fuel pump to push the fuel from the tank to the primary fuel pump. The kit is more expensive than probably the other remedies, but well worth it in my opinion. It is engineered to work with your systems so all of the safety features are there. With fuel in boats, that was important to me. it plugs right into your existing wiring harness. Mercruiser has a TSB on this problem. http://www.boatfix.com/merc/Bullet/99/99_07.pdf

It is reposted here and has links to the different part numbers. I would search the part # at other sources for possible better pricing.

https://www.perfprotech.com/blog/articles/mercruiser-vapor-lock

Edited July 28, 2015 by TeamAllen