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How stop whine on high pressure fuel pump 2002 Mercruiser MPI 5.0

M

mohlmann

New member
Folks,

I have 2002 Mercruiser 5.0 MPI with a Bravo 3 outdrive. I replace both the lift fuel pump ( low pressure) and the high pressure fuel pump ( high pressure i replace twice in an attempt to stop the whine)

the engine starts and runs perfectly.

the high pressure pump makes a high pitched and very annoying whine. any ideas on how to eliminate it?

thanks,
Rick
 
High pressure pumps tend to be noisy. That is why, at least on cars they have in tank pumps. So the solutions are soft mounting with a foam pad in a clamp so that the sound isn't transmitted to the mount point. or an in tank pump, I'm not sure if that is a thing in the marine world. Also These pumps are quieter if they aren't over capacity.

What I mean is that the tendency in the hot rod world is to buy the biggest baddest pump, you can, but the end result is that the pump is building pressure, and only a minimal fraction of it's potential throughput is being used. If you are only using a small fraction of it's pumping capacity it is essentially trying to pump the fluid up against a restriction, resulting in noise. An appropriately sized pump for your application will minimize the noise.

In a custom application this is a difficult thing to determine. Essentially you want your WOT fuel flow at the required pressure. So if your fuel consumption at WOT is 120 LPH at 60psi, then maybe you want a pump that is capable of 150 lph at that pressure, but you definitely don't want a 250 lph pump.

Having a return fuel system will also help some. Anyway I don't know if this helps at all as it's mostly related to my experience working on hot rods, not boats.
 
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