Clattering Noise in 1996 7.4 LX?

[Redhook98]

I have an intermittent clattering noise towards the front of my 1996 7.4L LX (with Bravo 3) engine. It is a fuel injected unit. The clattering is intermittent and does not seem to correspond to anything in particular. Hoping it is just a water pump going bad. I have a video, but can not seem to post it.... Help please! I need to go boating! Lol!

Really only notice at idle.

 

[Redhook98]

https://www.youtube.com/watch?v=TxNlIClTHnM&feature=youtu.be

 

[Redhook98]

Appears to be coming from the raw water pump/fuel pump assembly. What would make an intermittent clattering there, and only at idle/low RPMS? Is there a small pushrod or is the fuel pump working off a c am on the raw water pump shaft?

 

[alldodge]

When is the last time you checked and changed the gear lube in the pump reservoir?

 

[Redhook98]

In the pump reservoir? Which one? The outdrive reservoir? Just a week or so ago. It's a cenimeter below the full line, but good.

 

[Scott Danforth]

Not drive reservoir , the raw water pump / fuel pump reservoir. Right side of motor, about crank height

 

[Redhook98]

Do I pull the fuel pump off and refill? Or is there a port for this? Never had a Merc with this setup before. Can this cause the clattering in the video?

 

[alldodge]

Do I pull the fuel pump off and refill? Or is there a port for this? Never had a Merc with this setup before. Can this cause the clattering in the video?

Depends on which one you have. If you have one which has a plug in the bottom you can drain it and refill from the top. If not, its easy enough (if you can get to the pump) to remove the pump, fix it that way.

Look in my sig about raw water pump maintenance

 

[Redhook98]

Will try it first thing tomorrow. I appreciate the timely responses. This makes total sense with what I was seeing/hearing. 80/90w OK?

 

[Redhook98]

I pulled the fuel pump off and it was almost all gas. Black gas. I thought there would be a solid cam, but instead I see a loose ring that spins around the shaft. Is there supposed to be bearings in that ring, or is it loose? My water pump was not leaking and the bearings feel tight.

 

[harleyman1975]

I think you found the culprit!

 

[alldodge]

I pulled the fuel pump off and it was almost all gas. Black gas. I thought there would be a solid cam, but instead I see a loose ring that spins around the shaft. Is there supposed to be bearings in that ring, or is it loose? My water pump was not leaking and the bearings feel tight.

The shaft is a cam type lobe which the ring spins around it. If it had lube instead of gas, it would be quite. Look at items 15 and 16 in the link. They are simple enough to rebuild and cost about $60 to do so.

http://www.mercruiserparts.com/bam/s...31796/1614/330

Also time to replace your fuel pump

 

[Redhook98]

The shaft is a cam type lobe which the ring spins around it. If it had lube instead of gas, it would be quite. Look at items 15 and 16 in the link. They are simple enough to rebuild and cost about $60 to do so.

http://www.mercruiserparts.com/bam/s...31796/1614/330

Also time to replace your fuel pump

I ordered a new fuel pump today. $50 on Amazon can't be beat! I see even wear around the ring, so will try it with fresh gear lube and new pump. If that does not calm things down, I will rebuild or replace the water pump assembly entirely.

I saw lots of debris and crap in the clear hose coming off the fuel filter. I feel it has been leaking for some time. No degradation in performance that I could notice, but definately was leaking gas into the reservoir.

Thanks!

 

[Redhook98]

OK, got the new fuel pump on and it seems to take care of 99% of the clattering. Can still hear an occasional clatter, but not much. My big question though before I go out and buy a new raw water pump is "how much noise does the raw water pump make when it is good"? Am I supposed to hear the pump, or am I just to sensitized to anything making noise in that area now? It's hard to describe, but it is almost like a deep but subtle bearing noise. A hollow tube to that area does not tell me much. No grinding or anything out of the ordinary, I htink. Bearings and seals are tight though. New lube oil is in the pump. Am I worrying about nothing now?

 

[alldodge]

A good pump makes no noise, and you did fill the pump housing with gear lube?

 

[Redhook98]

A good pump makes no noise, and you did fill the pump housing with gear lube?

Its the pump. I did not see the trailer of oil under it. Although the bearings and seals looked good, they were not. It's got a bad bearing and seals. I found a brand new unit online for $315 complete and ordered it. New tensioner and belt while I am at it.