Official Cummins 6cta 450C thread

Forrestkk said:
Convince me, how can a zinc cause damage other than breaking up?
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You can over-zinc a boat. The bottom paint usually shows an over-zinc condition. It will blister and almost look like it was burned around thru-hulls and the like. There is a balance.
 
ttmott said:
You can over-zinc a boat. The bottom paint usually shows an over-zinc condition. It will blister and almost look like it was burned around thru-hulls and the like. There is a balance.
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I don't have any extras except the rudders. Would anyone remove zincs that came with the boat?
 
Forrestkk said:
I don't have any extras except the rudders. Would anyone remove zincs that came with the boat?
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Sorry, I was under the assumption you were putting additional anodes on the engines which is really flushing money down the swirl.
So, rudders.... Why have anodes on the rudders? Both of the rudders should be bonded (the heavy green wires) and the anode to protect those is the hull anode. If the wiring is in good order to the hull zinc there is no need for additional anodes on the rudders.
Trim Tabs are different; they are not bonded to the hull zinc and definately need their own anode.
Your struts are bonded inside the boat.
The only thing up for discussion is the prop and shaft. One school says to put an anode on the shaft as there isn't good enough continuity through the gear. Another school including SR says the props and shaft are adequately bonded through the gear.
The bottom line is, if the boat's metallic elements exposed to raw water are bonded to the hull zinc then no additional zinc is required. Things that are not positively bonded should have their own zinc.
 
I did a 3 hour run today the last hour the port engine was dropping between 200 and 300 rpm from 2,250rpm. It would quickly come back then a Minute later drop off again this happens with sync on or off

any ideas
 
Blueone said:
I did a 3 hour run today the last hour the port engine was dropping between 200 and 300 rpm from 2,250rpm. It would quickly come back then a Minute later drop off again this happens with sync on or off

any ideas
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I'd guess a barely loose fuel line. Fuel flow goes up, sucks air, fuel flow goes down, recovers, gains RPM, and repeat.
 
ttmott said:
Sorry, I was under the assumption you were putting additional anodes on the engines which is really flushing money down the swirl.
So, rudders.... Why have anodes on the rudders? Both of the rudders should be bonded (the heavy green wires) and the anode to protect those is the hull anode. If the wiring is in good order to the hull zinc there is no need for additional anodes on the rudders.
Trim Tabs are different; they are not bonded to the hull zinc and definately need their own anode.
Your struts are bonded inside the boat.
The only thing up for discussion is the prop and shaft. One school says to put an anode on the shaft as there isn't good enough continuity through the gear. Another school including SR says the props and shaft are adequately bonded through the gear.
The bottom line is, if the boat's metallic elements exposed to raw water are bonded to the hull zinc then no additional zinc is required. Things that are not positively bonded should have their own zinc.
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I didn't install the rudder zincs. Came that way, but tracking on not being needed.

Agree, would not add engine zincs, but would also not remove what it came with from the factory.
 
Blueone said:
I did a 3 hour run today the last hour the port engine was dropping between 200 and 300 rpm from 2,250rpm. It would quickly come back then a Minute later drop off again this happens with sync on or off

any ideas
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Racors full? Pinched O-ring at Racor change out?
 
Blueone said:
I did a 3 hour run today the last hour the port engine was dropping between 200 and 300 rpm from 2,250rpm. It would quickly come back then a Minute later drop off again this happens with sync on or off

any ideas
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Just had a thought....was the engine actually dropping RMP that you could feel it or was it just an indication on the Tach?
 
Blueone said:
I did a 3 hour run today the last hour the port engine was dropping between 200 and 300 rpm from 2,250rpm. It would quickly come back then a Minute later drop off again this happens with sync on or off

any ideas
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A few thoughts. Assuming no black smoke, could be air in the fuel system, bad lift pump (letting air into the fuel system) racor letting in air or partially blocked tank vent. Chance it could be fuel filters. Start simple, check fuel valves to make sure one isn't partial closed, check racor for air. If you have drag needle vac gauges, see if it was pulling too much vac. Drain a little fuel out of the racor drain looking for water. If you don't get it sorted by the time you move again, send someone down into the bilge to look at the vac gauge on the racor while it's acting up if you don't have the drag needles. Possibly could be a partially clogged secondary (on engine 5285) filter if you are running 30 M in the racors. . Good luck
 
my3sons said:
A few thoughts. Assuming no black smoke, could be air in the fuel system, bad lift pump (letting air into the fuel system) racor letting in air or partially blocked tank vent. Chance it could be fuel filters. Start simple, check fuel valves to make sure one isn't partial closed, check racor for air. If you have drag needle vac gauges, see if it was pulling too much vac. Drain a little fuel out of the racor drain looking for water. If you don't get it sorted by the time you move again, send someone down into the bilge to look at the vac gauge on the racor while it's acting up if you don't have the drag needles. Possibly could be a partially clogged secondary (on engine 5285) filter if you are running 30 M in the racors. . Good luck
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No black smoke
 
Blueone said:
I did a 3 hour run today the last hour the port engine was dropping between 200 and 300 rpm from 2,250rpm. It would quickly come back then a Minute later drop off again this happens with sync on or off

any ideas
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I went down there today and went over everything and saw no evidence of any problems….. I ran it up at the dock it ran fine. Took it a half hour up the river ran perfect….. so scratching my head here
 
How much vacuum were you pulling when under a load? How much fuel was in the tank? If tank was low you could have picked up something on the pickup tube.
 
Burg guy said:
How much vacuum were you pulling when under a load? How much fuel was in the tank? If tank was low you could have picked up something on the pickup tube.
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I don’t have vacuum gages…. I am all mechanical. I was about 1/3 full
 
Sorry, I should have been more clear. Most racors have a vacuum guage on the top and some have a tee-tale that will mark how high the suction was on the racors.
 
Blueone said:
I did a 3 hour run today the last hour the port engine was dropping between 200 and 300 rpm from 2,250rpm. It would quickly come back then a Minute later drop off again this happens with sync on or off

any ideas
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Try cleaning or change your racor ...... had the same thing happen last year --- directly attributed to getting dirty fuel and pushed to RACOR. Easy fix.
 
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