merc 502 mpi vapour lock ?????
09-25-2007, 04:22 PM
#12
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jayhawk dont rekon they have ever had the pump looked through all the paperwork ive never had the upgrade.
hi jerry mine is also the starboard engine really weird but so damn frustrating merc delear is going to look at it next week,if i cant cure it before and save dollars!!!!!!!!!!!!!!1
hi jerry mine is also the starboard engine really weird but so damn frustrating merc delear is going to look at it next week,if i cant cure it before and save dollars!!!!!!!!!!!!!!1
09-26-2007, 12:42 PM
#13
Jerry B
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From everything I have read this is a comon problem. Fresh air just doesnt get into a parked boat engine compartment. When we set in ours we climb accross the hatch all the time so leaving it open is not an option. I guess I'm going to try running the blowers some at different intervals. I dont see leaving them on for long periods while sitting.
I may try Marval mystery oil. I have used it some but not as a fuel additive.
I have a theroy on why the starboard engine on mine vapor locks and not the port. The VST tank is close to two exhaust manifolds on that engine and central to the engine compartment where the heat may be the greatest where as the port is only close to one exhaust manifold and also close to a vent area so maybe it stays just a bit cooler. Just a therory.
Sounds like some do this worse than others. Mine always restarts. Then it dies right after throttle up. Then it's a bit hard to restart but then no problem untill the next hot soak.
It is anoying.
Jerry.
I may try Marval mystery oil. I have used it some but not as a fuel additive.
I have a theroy on why the starboard engine on mine vapor locks and not the port. The VST tank is close to two exhaust manifolds on that engine and central to the engine compartment where the heat may be the greatest where as the port is only close to one exhaust manifold and also close to a vent area so maybe it stays just a bit cooler. Just a therory.
Sounds like some do this worse than others. Mine always restarts. Then it dies right after throttle up. Then it's a bit hard to restart but then no problem untill the next hot soak.
It is anoying.
Jerry.
09-26-2007, 01:08 PM
#14
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vapor lock
i had a similar problem with my engines when i had my sonic. Ask your tech about Brady Check Valves. They are fairly easy to install and stopped the problem....
09-26-2007, 03:15 PM
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hi eric where did you get the brady check valves , sounds interesting.any help is good ,the merc guy is coming over next week later part!
hi jerry b , your problem is the same as mine you explained it exactly,from cold ie not used it at all that day it normally starts ok, you go for a run ,i always idle for a bit before shut down always run the blower at idle etc, you can stop for at least an hour go to re start first time you think great got it, then as you go to throttle up it dies, even tried giving it little more revs once started but that doesnt work ,as you say it eventually restarts but now mine is taking longer and longer every time some times upto 15 mins of keep trying ,it always happens in a busy area manouvering for gas or in a marina ,and your going aaaaarhhhhhhhhhhhhhhh damn thing !!!!!!!!!!!!ill let you all know how it goes!
hi jerry b , your problem is the same as mine you explained it exactly,from cold ie not used it at all that day it normally starts ok, you go for a run ,i always idle for a bit before shut down always run the blower at idle etc, you can stop for at least an hour go to re start first time you think great got it, then as you go to throttle up it dies, even tried giving it little more revs once started but that doesnt work ,as you say it eventually restarts but now mine is taking longer and longer every time some times upto 15 mins of keep trying ,it always happens in a busy area manouvering for gas or in a marina ,and your going aaaaarhhhhhhhhhhhhhhh damn thing !!!!!!!!!!!!ill let you all know how it goes!
09-26-2007, 05:41 PM
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I had a similar problem with 1997 502 MPIs earlier this year. One response to the thread I posted suggested using Marvel Mystery oil in the fuel (it raises the fuel vaporization temperature). I have been adding it since and have not had a stumble/stall/hard restart since then. My engines have VST (Vapor Separator Tanks) which I disassembled and cleaned but did not find anthing unusual. The VST system does not have a schrader valve but there is a plug on the top of the VST which can be removed to release pressure in the tank itself. I was going to try this but the problem has not repeated. Good Luck.
09-27-2007, 08:43 AM
#18
Jerry B
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Inspector: Thanks. I found a can of Mystery Oil in our shop. I didnt know that using it as a fuel additive was one of it's many uses but it does state on the lable how to mix. I will try it next year when it gets hot again.
Jerry.
Jerry.
09-27-2007, 12:00 PM
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I chased same issue with 500 efi motor, thought for sure it was vapor lock, tried all steps to avoid with no solution.
Ended up being "heat " expansion of full pump armiture.
Replaced full pump and all has been well ever since.
Ended up being "heat " expansion of full pump armiture.
Replaced full pump and all has been well ever since.
