NCDS2000

Can I open the vst unit and look at screens and stuff with out buying parts or once you open them do you need new gaskets and such?

NCDS2000

Both engines reading 32 psi at idle and drop to 28 at 1800 rpm seems low for both gonna run it now and see what happens changing water separators now on both

NCDS2000

Mechanical fuel pump is not pumping anything and engine will not run at all so I guess we have our answer I removed the screw and it's got gas in it. Anyone have a link on replacement​ looks super easy but how much oil and what type to fill it with and do I replace just the pump or the pump and housing.

SB

iTrader: (1)

If engine is not running. how do you know the mechanical pump is not pumping anything ? IE: what was your test method ?

NCDS2000

0 fuel pressure removed output line right off pump cranked engine no fuel at all engine had fuel pressure earlier in day we got on it under load and engine quit I watched fuel pressure drop right off and engine quit after that 0 fuel psi then checked lower housing where pump sits on and filled with oil and gas

NCDS2000

waiting on mechanical pump, thank you guys for all your help so far. I was thinking in my head that the original issue may be different then just this mechanical pump but will have to wait and see.

Here is what doesnt add up to me before the engine quit i had a fuel gauge on both engines running at idle they were both identical 33 psi. that seems low to begin with. When i brought the rpms up the psi went down to about 28 ish maybe 29 but never below 28.

what is your guys opinion about this fuel pressure?

both engines were identical before the one died completely mind you then as that engine died i was watching the fuel pressure go right down to 0. Like i said i removed the output line on the mechanical pump and cranked engine and 0 fuel output not even a dribble. I told my buddy i still think there may be an underlying issue but hopefully it is just this dumb pump.

Just before i left today i pulled the pump off lobe covering is ok no drastic wear on pump arm or lobe cover but loaded with gas and oil. Cleaned it all out prepped it with new oil and waiting.

SB

iTrader: (1)

PSI will go down when bringing up the rpm on the trailer. No load and higher rpm = more intake vacuum. Vacuum is attached to regulator. Higher vacuum lowers fuel psi.

When you put boat in the water and increase rpm in gear intake vacuum will go down which makes the fuel psi raise.

As far as the base fuel psi at idle, depends on your motor. Some 502's where near yours, other where higher psi.

NCDS2000

thank you so much for all the assistance. that made total sense cause i did see a rise in fuel pressure under load in the water exactly how you stated above.

so i am hoping it is just the mechanical pump then.

the other one died last year, i was not around to help him with it. the water housing was leaking into the oil for the pump and they replaced the whole housing they went to install the old pump back on it and it was dead between housing replacement and the pump they charged him 1300 i was like wtf. I think they ripped him off

SB

iTrader: (1)

Compared to doing it yourself it will sound like a ripoff, but it is not for a shop to do it. Those sea water pumps are expensive.
Discounted at $710.00 http://www.mercruiserparts.com/bam/s...31902/1614/330
Fuel pump discounted at $223.50 http://www.mercruiserparts.com/bam/s...31902/1614/130

Put it this way, how much do you think the VST units where from Merc when they where available ?

Hint, it rhymes with $2,000.

http://www.mercruiserparts.com/bam/s...31902/1614/150

NCDS2000

Oh I know all about expensive parts I work for Mercedes-Benz
i guy I know just replaced his brakes on his s63 AMG at the tune of 7800 dollars parts were 7200 of it.