I was told people are converting from mechanical fuel pumps on Merc 5.7 carb engines to electric fuel pumps because of E10 gas and mechanical fuel pumps.
Fuel pumps in carb engines
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Boat fuel pumps are designed and built, to drain gas into the motor if the diaphram leaks. You can't do that with a electrical "use it on anything" type of fuel pump. Marine carbs also route the overflow tube back into the motor so you don't dump fuel into the bilge.The alternator is designed to contain any sparks. That's why Marine parts cost more then car parts.,,,
There must be electric fuel pumps for boat engines.
Originally Posted By: BigCahuna
Boat fuel pumps are designed and built, to drain gas into the motor if the diaphram leaks. You can't do that with a electrical "use it on anything" type of fuel pump. Marine carbs also route the overflow tube back into the motor so you don't dump fuel into the bilge.The alternator is designed to contain any sparks. That's why Marine parts cost more then car parts.,,,
huh I didn't know that. That's pretty cool!
Boat fuel pumps are designed and built, to drain gas into the motor if the diaphram leaks. You can't do that with a electrical "use it on anything" type of fuel pump. Marine carbs also route the overflow tube back into the motor so you don't dump fuel into the bilge.The alternator is designed to contain any sparks. That's why Marine parts cost more then car parts.,,,
huh I didn't know that. That's pretty cool!
A lot of folks are installing a booster pump (low pressure electric in-line pump) to help the mechanical pump on their boats. Some on an intermittent push button switch so you can overcome momentary fuel starvation, some on all the time...
Something like this Vertex unit: http://www.ebay.com/itm/112057409735?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
The thing about Gasahol is 1.) it absorbs water, so you end up with wet fuel and that can corrode an old style mechanical pump; and 2.) E-10 and E-15 vapor lock easier that pure gas, so between the vacuum pulling the fuel from a low tank, and the easier vapor state, some mechanical pumps will not do what you want ...
And if you add a fuel/water separator to the system, that is more restriction than some old pumps can deal with. Especially if the check valves have pitted and corroded in the pump so it's not 100% anymore ...
Something like this Vertex unit: http://www.ebay.com/itm/112057409735?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
The thing about Gasahol is 1.) it absorbs water, so you end up with wet fuel and that can corrode an old style mechanical pump; and 2.) E-10 and E-15 vapor lock easier that pure gas, so between the vacuum pulling the fuel from a low tank, and the easier vapor state, some mechanical pumps will not do what you want ...
And if you add a fuel/water separator to the system, that is more restriction than some old pumps can deal with. Especially if the check valves have pitted and corroded in the pump so it's not 100% anymore ...
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From reading it looks like the newer mechanical pumps are now designed for E10.
The mechanic working on my boat found a bad fuel pump and decided to replace with electric. Did not ask me. You need to power the pump and cut the power if engine stops. So cost of the pump and sensor/relay. And deal with the carb overflow tube.
I never had a problem with E10. Boat came with water separator installed on the engine.
The mechanic working on my boat found a bad fuel pump and decided to replace with electric. Did not ask me. You need to power the pump and cut the power if engine stops. So cost of the pump and sensor/relay. And deal with the carb overflow tube.
I never had a problem with E10. Boat came with water separator installed on the engine.
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So now I have an electric pump, sensors, relay, etc and if any part fails I am stuck. Maybe carry a new mechanical pump & fittings on board.
That pump relay needs to either be driven off of the alternator "tach" output, or on an oil pressure switch with initial power supplied by the second terminal on the starter.
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