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Bob C.

95 Echelon Vapor lock

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Bob C.

I own a 1995 Echelon, throttle body fuel injection, 350 mercruiser.

In the past 2 years we have had vapor lock problems. After the 1st. year, installed new fuel line, new low pressure pump and rebuilt vapor separator tank(replaced needle valve, diaphram and gaskets). It appears that the high pressure fuel pump is Okay.

This year returned from ski trip to Lake Trinity in Ca. and again had vapor lock issues. Symptoms are, engine won't start when engine compartment is hot, either during a hot midday temp.(around 100 degrees). I have solved this problem temporarily by opening engine cover and placing cold wet towels over fuel lines and vapor separator tank.

Question: Why has this become a problem in the last two years? From what I have read in this forum, the fuel lines can be insulated with foam tubing insulation. What about the vapor separator tank?

Question: A friend has an boat, different make, inboard with an out drive, uses the same fuel, on the same lake, but never has a vapor lock problem. Maybe his engine compartment is more insulated from the heat and maybe his fuel lines are insulated, also, his boat is 1989 era, no TBI, but carburetion.

Edited by Bob C.

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martinarcher

Mine is a carbed Merc as well. These late 80's motors has the mechanical low pressure pumps (at WOT my fuel rail is about 8-9psi versus your 50psi on an Fuel Injection fuel rail) so vapor lock doesn't occur on the old carb motors. I would give the fuel line insulation a shot I know I have seen claims from other members claiming it solved their vapor lock issues. If it is only happening at mid day extreme temps, it sounds like you would only have to knock the fuel line temps down a little bit to keep under the vapor lock temp.

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Bob C.
Mine is a carbed Merc as well. These late 80's motors has the mechanical low pressure pumps (at WOT my fuel rail is about 8-9psi versus your 50psi on an Fuel Injection fuel rail) so vapor lock doesn't occur on the old carb motors. I would give the fuel line insulation a shot I know I have seen claims from other members claiming it solved their vapor lock issues. If it is only happening at mid day extreme temps, it sounds like you would only have to knock the fuel line temps down a little bit to keep under the vapor lock temp.

I am kind of new with the tech stuff. Your boat is a '88, carbed, mercruiser. Mine is a '95, TB injection, mercruiser. Is the TBI considered carburetion or fuel injection? What is WOT? Fuel rail is the fuel line delivery system and my '95 boat has a higher psi, which sounds like it has more issues with vapor lock. Are fuel mixtures provided on Calif. lakes causing more problems, such as being more heat sensitive? Thanks, Bob

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martinarcher
Mine is a carbed Merc as well. These late 80's motors has the mechanical low pressure pumps (at WOT my fuel rail is about 8-9psi versus your 50psi on an Fuel Injection fuel rail) so vapor lock doesn't occur on the old carb motors. I would give the fuel line insulation a shot I know I have seen claims from other members claiming it solved their vapor lock issues. If it is only happening at mid day extreme temps, it sounds like you would only have to knock the fuel line temps down a little bit to keep under the vapor lock temp.

I am kind of new with the tech stuff. Your boat is a '88, carbed, mercruiser. Mine is a '95, TB injection, mercruiser. Is the TBI considered carburetion or fuel injection? What is WOT? Fuel rail is the fuel line delivery system and my '95 boat has a higher psi, which sounds like it has more issues with vapor lock. Are fuel mixtures provided on Calif. lakes causing more problems, such as being more heat sensitive? Thanks, Bob

Sorry Bob,

WOT is Wide Open Throttle or maximum throttle. The carbed engines require much less fuel pressure. You engine has fuel injection. The higher pressure is required for the fuel injectors to properly spray a conical anatomized pattern of fuel into the engine. If you were to run a fuel injected engine on the fuel pressure delivered by a carb fuel pump you wouldn't get a nice spray from you injectors (think of a garden hose with your thumb over it - the higher the pressure the nicer the spray you get). While fuel injection is a great thing which gives you many things such as better fuel economy, more consistent fuel mixture, better overall performance, usually high reliability, they do require a higher fuel pressure which can be prone to vapor lock since fuel under pressure gets warmer than fuel at a low pressure.

Hope this helps explain thing a bit better.

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Bill_AirJunky

Several years ago I had a vapor lock problem in my 94 PS205 with the TBI 350 in it. We experieneced it several times, typically on hot days, ie; over 90 degrees, after we were puttering around the lake at idle speeds, which is probably the hottest the motor is running, not a lot of wind or water flow at low RPMs. I'd cut the engine, sit for a bit, then try to restart it. Many times it would act like the battery was dead, turning over very slowly, then abruptly start up. But a few times it would not start at all. Almost like there was no spark. I'd check the spark & look down into the TBI to see fuel spraying. Everything seemed fine. 30 or 45 minutes later, it would start right up like there had never been a problem.

I talked to MC & Indmar about it a few times & guys at both insisted there was no way I could have vapor lock issues with an EFI system.... even though the TBI is not really true EFI, but a glorified computer-controlled carb.

In my search to find the solution, I called the guys at Skidim.com. They suggested the fuel line insulation kit. It was a whopping $13. I don't know why it worked, it's totally black magic to me, but insulating the fuel lines definitely did the trick.

I can't begin to think why it would be fine, then just start effecting you recently. Other than maybe something about your routine has changed in the last 2 yrs. Maybe give the guys at Skidim.com a call & see what they have to say about it?

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Bob C.
Mine is a carbed Merc as well. These late 80's motors has the mechanical low pressure pumps (at WOT my fuel rail is about 8-9psi versus your 50psi on an Fuel Injection fuel rail) so vapor lock doesn't occur on the old carb motors. I would give the fuel line insulation a shot I know I have seen claims from other members claiming it solved their vapor lock issues. If it is only happening at mid day extreme temps, it sounds like you would only have to knock the fuel line temps down a little bit to keep under the vapor lock temp.

I am kind of new with the tech stuff. Your boat is a '88, carbed, mercruiser. Mine is a '95, TB injection, mercruiser. Is the TBI considered carburetion or fuel injection? What is WOT? Fuel rail is the fuel line delivery system and my '95 boat has a higher psi, which sounds like it has more issues with vapor lock. Are fuel mixtures provided on Calif. lakes causing more problems, such as being more heat sensitive? Thanks, Bob

Sorry Bob,

WOT is Wide Open Throttle or maximum throttle. The carbed engines require much less fuel pressure. You engine has fuel injection. The higher pressure is required for the fuel injectors to properly spray a conical anatomized pattern of fuel into the engine. If you were to run a fuel injected engine on the fuel pressure delivered by a carb fuel pump you wouldn't get a nice spray from you injectors (think of a garden hose with your thumb over it - the higher the pressure the nicer the spray you get). While fuel injection is a great thing which gives you many things such as better fuel economy, more consistent fuel mixture, better overall performance, usually high reliability, they do require a higher fuel pressure which can be prone to vapor lock since fuel under pressure gets warmer than fuel at a low pressure.

Thanks very much, very helpful. Bob

Hope this helps explain thing a bit better.

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Bob C.
Several years ago I had a vapor lock problem in my 94 PS205 with the TBI 350 in it. We experieneced it several times, typically on hot days, ie; over 90 degrees, after we were puttering around the lake at idle speeds, which is probably the hottest the motor is running, not a lot of wind or water flow at low RPMs. I'd cut the engine, sit for a bit, then try to restart it. Many times it would act like the battery was dead, turning over very slowly, then abruptly start up. But a few times it would not start at all. Almost like there was no spark. I'd check the spark & look down into the TBI to see fuel spraying. Everything seemed fine. 30 or 45 minutes later, it would start right up like there had never been a problem.

I talked to MC & Indmar about it a few times & guys at both insisted there was no way I could have vapor lock issues with an EFI system.... even though the TBI is not really true EFI, but a glorified computer-controlled carb.

In my search to find the solution, I called the guys at Skidim.com. They suggested the fuel line insulation kit. It was a whopping $13. I don't know why it worked, it's totally black magic to me, but insulating the fuel lines definitely did the trick.

I can't begin to think why it would be fine, then just start effecting you recently. Other than maybe something about your routine has changed in the last 2 yrs. Maybe give the guys at Skidim.com a call & see what they have to say about it?

Thanks for your help, I will check with Skidim.com

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dalt1

Ethanol fuel contains alcohol which vaporizes easier than fuel. I have had issues the last 2 years with my 06 Monsoon. My area of the country just started using 10% ethanol fuels for the last 2 years. I never had problems for the 2 years before that. I have talked to Indmar techs and they agree with the diagnosis. They have a secondary low pressure fuel pump that installs before the original pump. That pushes cool liquid fuel past the vapor locked lines to the original pump to keep you going. I have not gone that route yet as I know if I open my center engine hatch for a bit to let out the hot air, I can keep it from locking up. The pump kit was somewhere around $240.

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coldwater-echelon

I totally agree with the ethanol theory. Several weeks ago a few ski buddies and myself were talking about this very issue. I have a '93 Echelon LX with a carbed 350 motor. When I run the motor for a long time and shut it down for say 10 minutes or more it crankes a few times before it starts, the longer it sits the more it cranks. My guess is that ethanol flashes to a gas at lower temperatures than gasoline does so, what is happening is the ethanol in the float bowl is flashing off and the motor has to crank over a few times to replenish the fuel that was lost. It has been getting worse as the last few years go by and as the ethanol content goes up. My motor never use to do this and has been a recent thing in the last few years. As I said, I have this problem and several of my ski buddies with carbed and fuel injected motors. The government thinks ethanol is great but to us boaters it is horrible and frustrating.

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Michigan boarder
I totally agree with the ethanol theory. Several weeks ago a few ski buddies and myself were talking about this very issue. I have a '93 Echelon LX with a carbed 350 motor. When I run the motor for a long time and shut it down for say 10 minutes or more it crankes a few times before it starts, the longer it sits the more it cranks. My guess is that ethanol flashes to a gas at lower temperatures than gasoline does so, what is happening is the ethanol in the float bowl is flashing off and the motor has to crank over a few times to replenish the fuel that was lost. It has been getting worse as the last few years go by and as the ethanol content goes up. My motor never use to do this and has been a recent thing in the last few years. As I said, I have this problem and several of my ski buddies with carbed and fuel injected motors. The government thinks ethanol is great but to us boaters it is horrible and frustrating.

Same thing here. I recently bought the boat, but knew it well from the owner who is a close friend. Never did it in years past. Seems funny to pump the throttle twice before starting, when I just ran it 15 minutes ago. Just something to get used to I guess.

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dalt1

And now there is talk of raising to 15% ethanol. I hope it don't happen.

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BillFooter
And now there is talk of raising to 15% ethanol. I hope it don't happen.

It's part of the 'Change that you can believe in." Cry.gif

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fambu

British Columbia: all 94-octane Chevron fuel is ethanol-free.

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