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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 11074
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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Customer Question

Hi there
Submitted: 2 years ago.
Category: Boat
Expert:  Tan replied 2 years ago.
Hello. My name is ***** ***** won't keep engine from turning over. It will keep the engine from starting but not turning over. So is it not starting or not turning over?
Customer: replied 2 years ago.
I am in Arizona. 110 degrees today. Boat starts fine in the morning. Then, if I shut the boat off and let it sit for 10-15 min it will not start. It feels like it is not getting enough fuel to start. If I play with the throttle sometimes it will start. I can hear the fuel pump turn on. I am also getting fuel through valve on top of the engine. So, seems like there is pressure. But, I don't have a gauge to test the fuel pressure.
Customer: replied 2 years ago.
Any ideas on what would prevent it from starting? The reason I think it is vapor lock is because of the excessive temperature.
Customer: replied 2 years ago.
I am just unclear how to fix this so it does not re-occur.
Expert:  Tan replied 2 years ago.
Ok I understand I'm in Tombstone Az. myself. The things you can do are keep the blower running when you slow the boat down and while it sits. Open the engine cover while sitting. What happens with vapor lock is the when the engine is shut off the fuel actually boils in the fuel lines turning in to a vapor. Fuel vapor doesn't combust it has to turn back into liquid form be fore it will combust again. So all you can do is use high test which has to be a higher temp to turn to vapor or cool the fuel as best you can with ventilation. The engine compartment only needs to be 176*F for fuel to turn to vapor. So when you are sitting the engine temp climbs raising the temp causing the vapor lock. Try this and see if it helps with your situation. Post back with findings.
Expert:  Tan replied 2 years ago.
Here is a service bulletin on vapor lock from Mercruiser. Most of this applies to all marine engines.
Post back with questions.