what is killing my fuel pumps?
 

boat is a 1978 scarab with twin 502's that have been converted to carbs. bought the boat 2 months ago, both motors ran and fuel pumps worked. needed lots of little things here and there like bellows oil and gear lube change etc. Spent my free time getting it ready for the water but both fuel pumps died at the exact same time while the boat was parked. Both motors were working on a sunday, towed it 200 miles from my parents house to mine, and monday they wouldn't start. It's as if overnight the fuel pumps died. Ordered replacements from JEGS, they are just carter electric pumps...seem pretty simple. I installed them and was back to running status. maybe 3 min of runtime on the hose before being parked for 2 weeks due to weather and busy schedule. Go to start it and the port side pump is dead. Has power and oil pressure switch is functioning, but the pump is just dead. I sent it back to jegs and got another one, and in the week I spend waiting the starboard pump stopped working.

So that's a total of 4 fuel pumps that have died in a 1 month period with maybe 10 min of run time total. The fuel in the boat had been drained before running. At my parents house I could only get fuel with ethanol so I put 10 gallons in (figured I would burn through it pretty fast) and now that I'm home I added another 20 gallons of non ethanol fuel.

Not familiar with your brand of pumps but went thru a similar issue with electric pumps on a big boat that the electric pump was used as a lift pump to bring fuel to a diesel generator.

After going thru a few I got some info from my buddy who owns a autoparts store that almost all pumps are not meant to be subjected to having to lift the fuel from a depth of more than a couple inches and more than a foot or 2 for length.

He told me they were getting hot trying to draw the fuel up from such a depth of 18 inches that i had to pull fuel from and that was why they were failing.

He said the pumps are designed to push fuel not pull it so much .

Lowered the mounting of the pump and never had another problem

I am sure there are many on here who know more ,

I will certainly give that a look, and i've got the space to drop them about 10 inches if that will make a difference. they also have a fuel filter in line before them if that makes a difference, but the paperwork that came with the pumps says that's how they're supposed to be setup; after the filter

2 things:

1) Some electric fuel pump manufacturers still use epoxy to adhere the magnets to the motor structure. Ethanol fuel can/will eat most of the epoxy used by those manufacturers and thus the pump eat's itself.

2) Cavitation. As mentioned above - if the pump is not gavity fed fuel, it can and will cavitate and burn itself out.

Note: Big issue with #1 is, you'll be hard pressed to find someone in that company that not only understands this but also can tell you if they use epoxy or 'weld' the magnets on.

If you can get yourself mechanical pumps, do so, and end most of your pump worries forever or near forever.

This is an issue with our drag car engines. You are supposed to mount the pump as low as the pickup or lower, to gravity feed the pump. As stated, they usually push fuel better than pull it. Most pumps will state how to mount them properly.

I have noticed since getting into the boat market that some electric pumps are mounted higher and further away from the tank. I'd suspect these pumps are better suited for pulling fuel. Maybe try a different pump or call Carter and tell them what you've got going on.

How do you beat a Diaphragm when trying to pull fuel up ?

As far as some electric pumps being further away and higher ? Yeh, some elec pumps are better than others but they still stink at it. A reservoir like a fuel seperator/filter canister being higher than the pump can help. But..........

^^I totally agree^^

This could also be a wiring issue. Maybe there's no relays on the pumps and they're burning up from lack of proper voltage or current?

Yep, I was typing a response to check voltage earlier and got sidetracked.
Check it right at the pump.
Electric motors DO NOT like to be run under their rated voltage.

you beat me to it,,i was gonna say its his fuel,,needs e85 pumps lol..

Motors are designed to run at a given rpm.
When a motor is not supplied with its rated voltage the motor pulls more current to keep the rpms up and the extra heat from the increased current burns up the windings.