5.0 Mercruiser MPI Question After Stalling On Me This Weekend

bajaboats

Cadet
Joined
Sep 8, 2021
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8
2004 Mercruiser 5.0 MPI - SN: 0W011661
Alpha Drive

I put my boat in the water on Saturday and it ran perfect. After a few trips up the lake, I was idling into an area we park and hang out at. I noticed the boat begin to idle and sound rough. It eventually died all together. After that, the boat would start fine, but immediately die shortly after. If I attempted to rev the engine it would die. It was like it was starving for fuel.

The next day, I took the boat and filled it completely full with gas. It took 37 gallons to fill it up, and since it was a 50 gallon tank, that means I had 13 gallons in the tank. I got it home and hooked it to the hose. The boat started fine, started to act like it wanted to run rough, but then started running great. I allowed the boat to idle on the hose all the way up to temp. In total it ran for 30 minutes on the hose and sounded great.

I am left wondering what the issue was. I am putting a new fuel filter on it this week. When I did my seasonal maintenance, my ship only had a sierra fuel filter. This is the first time I've ever used a non-mercury fuel filter. Is my fuel pump failing? I wanted to see if anyone else has had a similar issue.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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did you inspect the contents of your fuel filter when you changed filters?

what is your fuel pressure? that will tell you the health of your pump?
 

alldodge

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I'm thinking you just might have ran out of gas.
Fuel gauges can be finicky and just stop going down to empty when running out. I've had one boat, a car and 2 trucks run out a bit below 1/4 tank

Have never been able to put X number of galls in a X number of gallon tank. Boat just doesn't sit level enough with vent and fill being the highest
 

Rick Stephens

Admiral
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Aug 13, 2013
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6,118
With an MPI system, clean fuel is everything. As Scott mentioned, dump your fuel filter into a clear glass container and see what you get back out. Use the best fuel filter you can get consistently and you will have few troubles with that fuel system.
 

bajaboats

Cadet
Joined
Sep 8, 2021
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8
Thanks all! I am going to pull the filter off when I get home from work today and inspect the contents. I got a new merc one ordered just in case. I got to work this morning and had it on my mind all morning and jumped the gun on making a post! I was really hoping being out of fuel possibly being the culprit, but I wasn't for sure since the pump clicked off at 37 gallons.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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do not reuse the old filter (because the dirty side mixes with the clean side when you pour the contents.)
 
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