2004 5.0 MPI mercruiser losing power, looking for help

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Ok, got bad info from son in law on fuel psi. Sorry.

checked it myself with new OTC gauge, ignition on pump pressures up to 40 psi and shuts off. Motor running at 1800 rpm, 37 psi. Pulled vac hose off of regulator, pressure comes up to 41/42 psi. I have read about a low psi pump prior to cool fuel system, do not see one on my boat.
serial# is om669798 if that helps. Could I install a 3/4 psi pump prior to spin on fuel filter as a booster?

Sounds like the regulator is failing...

Found this on line https://docplayer.net/46058600-Tabl...s-fuel-pressure-regulator-identification.html Had a look, and it's a great read. Plenty of good info on the regulator and pump theory of operations.

Chris........
 

Darwaypen

Cadet
Joined
Apr 7, 2019
Messages
16
Ran with fuel pressure gauge hooked up, up to 4800 rpm pressure remained 37-38 psi. Took vac hose off of regulator, pressure comes up to about 40-41.
 

alldodge

Moderator
Staff member
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Mar 8, 2009
Messages
40,581
Did you run it until it started loosing power or any kind of popping going on?

At those pressures I don't see it being the fuel pump.
 

Darwaypen

Cadet
Joined
Apr 7, 2019
Messages
16
No popping this time, but did lose its usual 1000rpm's after about 40 minutes of 4800-4900 rpm. pressure remained unchanged during the event. As usual slowed down putted around for a bit, acceleration was smooth, ran for about 15 min at the aforementioned rpm and lost power again. I can cruise all day long at 35 mph which is about 3800 rpm without issue, but that hard running brings something out in her. we've named her "Christine"
 

alldodge

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Mar 8, 2009
Messages
40,581
Guess, going to need a scan tool on the motor when it happens to see if any codes or faults show up
 
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