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Help with Engine Shutdown, Fuel Filter?

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I am looking for some advice.  I'm having a strange problem and I think it might be the fuel filter from the tank (not the water separator).  I was running the boat on Friday at varying speeds.  Spent some time at full throttle, and half throttle on Lake Michigan (<1ft waves).  I also spent some time at 1100 RPM on the Milwaukee river.  After an hour I left the river back onto the lake, and after about 5 minutes at full throttle the engine just shut down.  The engine restarted right away and as long as I kept it under 2300 RPM I was fine.  As soon as I went over that RPM the engine would shut down, but restart again right away.  I've never had the guardian kick in before, but I thought it just governed your RPM not allowing you to go over a certain point.  Does it shut your engine down? I have a Garmin 741 connected to my engine. There is no check engine light and all of the gauges look normal except the Fuel PSI which is reading 90 PSI even at idle.  Am I correct that fuel PSI should be about 43 PSI at WOT?  I'm guessing that the engine is shutting down because of lack of fuel, but it doesn't sound like its starving before it quits.

My first guess is the fuel filter and I will change that out first.  Does anyone have any other thoughts?

2002 Mercruiser 8.1L 496 / Bravo 3

Thanks for the Assist.

 

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Does your 8.1 have the cool fuel module? If so there is a removable screen at the base of the filter cavity, and another one on the suction of the primary fuel pump. I just did an 8.1 where an OEM Merc filter element had suffered from degradation of the element glue where the densite paper element attaches to the end plate. All the goo ended up in the screen at the base of the filter cavity.  W

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49 minutes ago, Senior said:

I do have a cool fuel module letter 'C' below

https://1drv.ms/u/s!AlN2qJ0_2_qu1Aowd0x-I1wZ9y35

Based on the exploded view below, are the removable screens you referenced listed?  If not could you point out where they are located.

https://1drv.ms/u/s!AlN2qJ0_2_qu1AtnZ6o8XA7c-xYV

 

Hopefully you can access the pictures from the links

Here is a better link that shows your cool fuel system. Yours was used on the Alpha equipped boats and does not have the screens I described. All filtration is done remotely. I would put a fuel pressure test gauge on your fuel rail and confirm that you have a fuel delivery issue before you chase ghosts.  W

http://www.marinepartsplus.com/catalog/mercruiser/serial/5.0L_MPI_ALPHA-BRAVO/8M0049000/15322-55

http://www.marinepartsplus.com/catalog/mercruiser/serial/5.0L_MPI_ALPHA-BRAVO/8M0049000/15322-75

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I'm revisiting this issue again hope someone can assist or at least tell me if this is in the realm of possibility.  I have had this same problem all summer with my engine shutting down after running it for about 30 minutes.  After it shuts down I can restart it right away but cannot go over 2300 RPM or it will shut down again.  I can rest the engine and let it cool down and it will be fine again.  I've tried numerous small things like filters and fluids.  I finally got it over to the repair shop to scan the engine and they couldn't find any codes so they started troubleshooting the old fashion way and found a dead plug.  They are currently as I'm writing this replacing all of my plugs.  So the question is does the symptom match the diagnosis?

Thanks for any help!!!

2002 Mercruiser 8.1L 496

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Had the exact problem on a 2008 Merc 8.1.

Cool fuel module was faulty, high pressure side would be intermittent. Put a fuel gauge on the schrader valve and when it starts happening watch for the fuel pressure to drop to zero, engine stalls, key off then on, back to 40 psi.

Replaced the entire module instead of R&R the parts and was fine for 3 years until I sold the boat.

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2 hours ago, paulswagelock said:

Had the exact problem on a 2008 Merc 8.1.

Cool fuel module was faulty, high pressure side would be intermittent. Put a fuel gauge on the schrader valve and when it starts happening watch for the fuel pressure to drop to zero, engine stalls, key off then on, back to 40 psi.

Replaced the entire module instead of R&R the parts and was fine for 3 years until I sold the boat.

Thanks for the response Paul.  I went to the marina and asked them to replace the cool fuel pump.  I also believe that the fuel sensor is on than module.  I thought the fuel pressure gauge was faulty because its pegged at 95 PSI.  It might be because the system truly has a fault. The pump module is only 4 deer without labor so fingers crossed that is the issue.

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I just wanted to provide a resolution to the problem I was experiencing with my 2002 8.1L Mercruiser shutting down unexpectedly after running it for 45 minutes.

To resolve the problem we needed to call the support engineers at Mercruiser.  The issue still existed after we replaced the Cool Fuel Pump.  It turned out to be the fuse for the starter.  It is apparently a known issue with this circa year Mercruiser 8.1L engine.   I got the boat back the day before I had to have it out of the marina for winter.  I was able to drive it on Lake Michigan from Milwaukee, Wisconsin to Racine, Wisconsin (20 miles) at 4000 RPM (speed was limited by the waves) without issue. 

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1 hour ago, Senior said:

I just wanted to provide a resolution to the problem I was experiencing with my 2002 8.1L Mercruiser shutting down unexpectedly after running it for 45 minutes.

To resolve the problem we needed to call the support engineers at Mercruiser.  The issue still existed after we replaced the Cool Fuel Pump.  It turned out to be the fuse for the starter.  It is apparently a known issue with this circa year Mercruiser 8.1L engine.  

Good to hear! Just to clarify, this is the 90 amp fuse on the starter motor itself? Part # 88-79023a91

Image result for 79023a91

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2 hours ago, Senior said:

  It is apparently a known issue with this circa year Mercruiser 8.1L engine.   

Too bad it was not a known issue with your mechanic. Would have saved you the cost of the fuel pump. 

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On ‎11‎/‎29‎/‎2018 at 11:41 AM, Shepherd1 said:

Good to hear! Just to clarify, this is the 90 amp fuse on the starter motor itself? Part # 88-79023a91

 

That was it!  I don't know how a fuse for the starter would effect the engine while its running, I leave that to you Shepherd. 

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16 minutes ago, Senior said:

That was it!  I don't know how a fuse for the starter would effect the engine while its running, I leave that to you Shepherd. 

The fuse is located on the starter positive battery terminal as a matter of convenience, but has nothing to do with starter function. The secondary side of the fuse feeds up to the engine power distribution harness that would provide primary power feed for ignition, injector coils, and electric fuel pumps. W

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It`s the reason I remove the ships Red power lead and go directly to the starters main post. See no reason to fuse 90A and have a inline 50A main power breaker too.

I leave the 90A in the alt charging circuit only

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   Somebody is not really solving the problem ???????????   How can a fuse act like a circuit breaker ?  When it is POORLY designed. The fuse is melting with less than 90 amps flowing threw it ??   Then cools down & reconnects internally time after time ?   Must be a Mercruiser or supplier NONE UL OR CSA approved design.  In a critical function.  Terrible standards.

A death trap in busy rivers & lakes with large ships & storms. 

A fuse is to protect the wires on the LOAD side of it.  The fuse can be rated & sized for any amount EQUAL TO OR LESS than the wire full load rating.

 

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