6-71 TI Can't reach max full load rpm

[Dan Mapes]

Covingtons 2500 NL, 2300 FL and the port only winds up to about 21 max. It was fine when we put it down for the winter. The last time this engine acted up the shutdown lever return spring had broken thus not fully retracting the lever. The lever is solid this time and feels retracted all the way. It hits a stop.
Exhast looks fine (white steam the boat has alway put out). Smooth idle, and lopes along in gear at idle well.
Temps and pressures are also good. Since I put pyrometers in this spring before launching I was able to see both engines tracking together. As did smoke at 1900. Seemed reasonably stable at 1900 but not completely.
While the SO drove I went into the bilge and it happened to falter. Just a blip not a solid shutdown sort of falter. Maybe 25-50 rpm. I did not see any cause in the throttle linkage. By the way this is the master for the glendenning.
I did not change the fuel filters at layup and really don't expect to find an issue there but they are coming out in a while when I get back down there. I decided to let things cool off a bit before I starting in.
We did not have the racks adjusted and if you know a good mechanic in the upper hudson valley that won't set these up like trucks it would help. Rumor has it one shop did that to a buddy and he lost a cylinder heading south. Something about a valve falling apart in is engine but those were stressed out 6v53's running over 400 hp I think.

[Nonchalant1]

Before you do anything else, change the fuel filters AND THE FINAL FILTERS ON THE ENGINE. The RACOR gets particles down to 30 microns and the final filter gets everything smaller. Those little filters take a long time to clog up, but when they do, you get the symptoms you are describing.

Doug Shuman

[Genesis]

Yep - change BOTH fuel filters, including the on-engine one.

If that does not resolve it, get an IR thermometer and shoot the exhaust ports UNDER FULL LOAD. If you find one port that is materially colder than the others (be careful as the parts you're screwing with are HOT and you need to be precise to shoot the same, and the hottest available, place at each exhaust port) you have a hole that is not getting good fuel flow.

That hole then deserves investigation (e.g. potential bad injector?)

[Dan Mapes]

Ok Guys

I was able to get back to the boat yesterday and pull the filters. Sorry I did not post earlier. The one on the right was from the port engine which would not spin up all the way.
These are 2 micron (over kill) filters and I believe the spin ons I converted to are 10.
My theory on this is that in the fall even tho we were good about maintaining the algaecide I gave it another shot before I warmed it with a short ride. Changed the oil and we put her down. When we took it out everything that had settled out made its way to the filters.
So I swapped out the racors and left in the spin ons. For now. We ran it a bit and sure enough the port engine perked up. When it cools down I'll pull the racors again and if clean, I will change the spin ons. If they fowl again I'll replace them until we clear it the mess out and then do the spin ons.

Nicely gummed up..

http://i252.photobucket.com/albums/hh40/danno53/filters.jpg

[REBrueckner]

Those filters sure look jet black, but it's hard to tell from the coloring and distance.

Was there material build up visible on the surface of the filters, visible crud particles, or just black color without any visible visible thickness.

You can avoid this problem, if it's a recurring annoying repeating one, by adding RACOR vacuum gauges...they'll indicate the restricted fuel flow via increased vacuum...and protect your injectors

[Skip]

The 2 MICRON filter is not a good idea because it will restrict engine fuel flow. The engine filter is suppose to be 10 mircons, with a 30 micron filter in front of the 10.

[Dan Mapes]

Skip I'd agree with that except we don't run the engines hard for extended periods of time. Along with this we watch the smoke along with other indicators frequently and have never observed issues.
Having pulled the filters in the past and wondered why I was changing them I have to consider that the 2 microns are acceptable for our application and help "polish" the fuel with regular use. I look at it this way. If we remove the algae before it has a chance to grow too far we're doing ourselves a favor.

These are 340 hp 6-71s with 1000ma filters. Our max consumption is about 20 gph per engine.

The 1000ma has a max flow rate of 181 gph. I looked around a bit but as yet I have not seen the flow rate they support with 2 mike elements.

[Silverado6x6]

I would agree about the filters actually being too fine as well. try the simple approach to any problem, you changed a parameter in the fuel system and it talked back.

[Dan Mapes]

We have been out with the boat since swapping the filters and the engines run up fine. I pulled the filters and there is no appreciable sediment on them so it looks like we had some algae settle out over the winter.
We're going to run it a bit more and ensure that we 'polish' it a bit since these engines return so much to the tanks.
They hit 2300 n/p now, and more. We probably need a prop tune up to get them back into shape. I might even add an inch or some cup to them.