Vapor Lock, Anyone Else?

[hre423]

So I just got my F29 with twin fresh ilmor 625s. It ran great first ride until we stopped and hung out for about an hour, then one of the motors would start right up and die after about a second. Mechanic is thinking vapor lock and that I just need to crack the hatch more and run the blower more often. Has anyone else had this issue? Any info is appreciated!

 

[NeedlesRat]

Here is an old thread regarding that.

Ilmor vapor lock

I love my 710 Ilmors except for one thing ..... Curious what you are doing or have done to fix or better yet cure the vapor-lock.

www.riverdavesplace.com

 

[plaster dave]

My buddy has an Eticket with illmors and if he doesn’t open the hatch as soon as he’s idling it will happen.
Mario at so cal speed and marine said he can fix the vapor lock issue on these motors.

 

[CanyonLakeDave]

Yep been there but have some great advice. Sent you a PM.

 

[pkrrvr619]

My buddy has an Eticket with illmors and if he doesn’t open the hatch as soon as he’s idling it will happen.
Mario at so cal speed and marine said he can fix the vapor lock issue on these motors.

Is this why I see people idling through channel with hatches open?

 

[FreeBird236]

Is this why I see people idling through channel with hatches open?

Even if you don't have a vapor lock problem, it keeps temps down and vapor levels down.

 

[Outdrive1]

It looks like your hatch is flat in your avatar. My F29 had the old school scoops built into it and it never vapor locked. My 33 Daytona vapor locked a lot, but it didn’t have scoops or anything in the hatches. Good thing is, it’s cooling down now. Crack the hatch when you’re idling and parked. It helps some.

 

[pkrrvr619]

Even if you don't have a vapor lock problem, it keeps temps down and vapor levels down.

Learn something new everyday. I’ve never done that and thought it was people just showing off their motors.

 

[lbhsbz]

I thought vapor lock went away thermoquad carbs and ‘70s dodge motorhomes.

How does a lake cooled fuel injected engine experience vapor lock?

 

[Big B Hova]

Those boats are made to go fast not idle!

 

[Outdrive1]

I thought vapor lock went away thermoquad carbs and ‘70s dodge motorhomes.

How does a lake cooled fuel injected injected engine experience vapor lock?

Mercury has a water cooled fuel cooler. The ilmors didn’t. At least not the models I had from the mid 2000’s. You could change the fuel system to include a bypass regulator and run a return line to the tank, that would solve the issue as well

 

[Todd Mohr]

Learn something new everyday. I’ve never done that and thought it was people just showing off their motors.

I always run my blower at idle speeds, gets fresh air running through the engine compartment. I've had it die after sitting and then a long idle out of the channel when you try to get on plane, , never does it I keep the blower on. It's a stock 1995 502 Magnum EFI. Not sure if it's vapor lock or lack of airflow.

 

[Your ad here]

So I just got my F29 with twin fresh ilmor 625s. It ran great first ride until we stopped and hung out for about an hour, then one of the motors would start right up and die after about a second. Mechanic is thinking vapor lock and that I just need to crack the hatch more and run the blower more often. Has anyone else had this issue? Any info is appreciated!

It is more than likely vapor lock. After doing a run and idling into a beach and hanging out for an hour the engine temps may be hotter than when you first parked. Look up heat soak. Hot engines and a closed hatch temps will continue to rise before they start to cool because there is no exit for the hot air and no entrance for fresh air. We had this problem with our jet boat in the summer. If we left the hatch closed it wouldn't start an hour later and the engine was too hot to the touch. If we put the hatch all the way up it would start an hour later and engine was warm to the touch.

 

[spectras only]

My Mirage only had the small side vents before I did install the old school scoops. The engines are 6.2 MPI's with cool fuel system. Never had a vapor lock even when the hatch is closed, idling. With two engines running wide open, there's a lot of heat under the hatch, so extra ventilation is the key. Don't get it why a high end builder can't figure that out,lol.
I had a Dodge Viper and that engine is a hot running one, even with the car's bottom open to vent.

My 72 Challenger 340 came with the phenolic body Thermoquad carb, never vapor locked. I have a 72 Volvo 1800 with fuel injection that has the vapor lock issue.Easy fix it, using a fiber washer on the injectors to insulate heat from the cylinder head.
A slighly fatter 'O' ring makes up the gap with the injectors further out.

 

[lbhsbz]

I had a Dodge Viper and that engine is a hot running one, even with the car's bottom open to vent.

Air needs to get in and air needs to get out. Cooling systems have a lot to do with pressures. When I built my V8 datsun, thing would cook after about 3 laps. The “open bottom” wasn’t helping…air pressure behind the radiator was the same as air pressure in front of it. I put a belly pan on it and added hood vents and that kept air from coming in the bottom, the hood vents lowered pressure in the engine compartment, the radiator saw airflow and all was well.

With wet headers and fresh water cooling or water to water heat exchangers…where is all the heat coming from?

 

[SJP]

Yes - with those motors it will happen in LHC. Here is what I did (take away at your own risk). On the Illmors there is a shraider valve on the fuel rail. I would cycle key kicking on fuel pump. Have a micro or shop towel and be Johnny on the spot with it. You can release the vapor but the fuel rail is very close to the exhaust header. Purge the vapor and air and you will get fuel out of valve. Obviously catch the fuel spray with the towel. Cycle fuel pump again and they will fire.

 

[spectras only]

Air needs to get in and air needs to get out. Cooling systems have a lot to do with pressures. When I built my V8 datsun, thing would cook after about 3 laps. The “open bottom” wasn’t helping…air pressure behind the radiator was the same as air pressure in front of it. I put a belly pan on it and added hood vents and that kept air from coming in the bottom, the hood vents lowered pressure in the engine compartment, the radiator saw airflow and all was well.

I have a 04 Miata with turbo. Have factory belly pan, but also have two hoods for the car. One with vents to run for track and one without for street ,lol.

 

[hre423]

Thanks for all the info everyone. Thought I would let it cool overnight and just be extra conscientious about leaving the hatch open at idle and running the blower often. Took it out to launch this morning and ran the blower for a few minutes prior to firing it and it idled great for about 5 minutes. Same motor shut off again and gave me the same issue and it wasnt even hot yet. Really confused. Almost sounds like a fuel issue, pump sounds different when primed than the port engine. Wish I could get it in a shop today but everything's closed

 

[n2otoofast4u]

Thanks for all the info everyone. Thought I would let it cool overnight and just be extra conscientious about leaving the hatch open at idle and running the blower often. Took it out to launch this morning and ran the blower for a few minutes prior to firing it and it idled great for about 5 minutes. Same motor shut off again and gave me the same issue and it wasnt even hot yet. Really confused. Almost sounds like a fuel issue, pump sounds different when primed than the port engine. Wish I could get it in a shop today but everything's closed

Sounds stupid, but those Illmors are SUPER picky about water in the fuel. Have you by chance added fuel to just that side? Did this start after getting fuel by chance?

 

[Javajoe]

Call Dillon at Image Marine. He knows Ilmors. My rebuilt 625 did the same thing twice right away. All good now. Just had to purge I guess. I didn’t do anything it just went away.

 

[calkid]

Possibly sucking air into the fuel system?

 

[hre423]

Sounds stupid, but those Illmors are SUPER picky about water in the fuel. Have you by chance added fuel to just that side? Did this start after getting fuel by chance?

I just got it and haven’t had to add fuel to it yet since previous owner topped it off before. The boat has been sitting for about a year and a half or so, so fuel might be bad.

 

[hre423]

Just realized a little bit of oil leaking from the drain plug as well. Going to try to see if I can get it in to Absolute tomorrow to try and get a diagnosis.

 

[SJP]

I just got it and haven’t had to add fuel to it yet since previous owner topped it off before. The boat has been sitting for about a year and a half or so, so fuel might be bad.

I would put 10 gallons of VP per side in.

 

[spectras only]

I'm guessing those Ilmors come with water separators, so change or empty those too.

 

[77charger]

Mines an old carb 350 mag and I swear couple years ago I had minor Vap lock issue at pleasant. Hot day went to eat left bar took off boat stumbled bad to get going idled fine take off again sputter etc finally cleared up.

I never lifted hatch to cool was only time it did this. Hot day too

 

[n2otoofast4u]

I just got it and haven’t had to add fuel to it yet since previous owner topped it off before. The boat has been sitting for about a year and a half or so, so fuel might be bad.

This right here answers the question in your other thread. Fuel (most likely ethanol) is old AF, probably been hot/cold 200 times in a storage unit over the last year, then you run it and it definitely gets hot from under hatch temps and the last of the real shit gasses off and you’re left with……..wait for it……. Shit fuel and most likely a bunch of moisture.

 

[Dog]

This right here answers the question in your other thread. Fuel (most likely ethanol) is old AF, probably been hot/cold 200 times in a storage unit over the last year, then you run it and it definitely gets hot from under hatch temps and the last of the real shit gasses off and you’re left with……..wait for it……. Shit fuel and most likely a bunch of moisture.

I was going to link this thread to the other thread when it was started but ...