New owner of a 38 Bertram Convertible with 6CTA 480ce's – immediate priorities?

[Nicholas]

Just closed on a B38 powered by 2002 6CTA’s with about 1500 hours. This is my first diesel boat so I’ve spent the last month or two pouring over this site and some others to get educated.

In 2016 the engines had heads rebuilt, turbos rebuilt, aftercoolers and heat exchangers serviced, and new injectors installed. One engine also had a piston, liner, rings, and bearings replaced and the other got a new belt tensioner and serpentine belt and had the exhaust pipe from the turbo to rubber boot rebuilt (not sure what happened there).

One engine blew a raw water hose during the sea trial, then in the second sea trial the other engine wouldn’t climb above 1900 RPM. However after the secondary fuel filters were changed the engines spun right up to just over 2600 and ran like a dream for several minutes with no issues.

My plan of attack is to change the motor and gear oil, change the zincs, racors, add a freshwater flush system, and replace any other hoses that look worn. Since the heat exchangers and coolers were done about 100 hours ago in 2016, i figured i could wait a year on doing those. I’m also going to go ahead and have about 100 RPM worth of pitch taken out of the prop. After all of the reading on this forum and others on the dangers of overloading these engines, and based on the fact that they seemed to have required a pretty major overhaul at 1400 hours, it seems to me like a prudent thing to do.

Is this logic reasonably sound? Anything else I should do right-away? Since he only did one of the belts should I go ahead and do the other? Thanks and I look forward to being a part of the community!

Topic

[Nicholas]

just pitched down again – now what?

After seeing my fuel burn numbers go up through the summer to where I was well above the desired curve, I just pitched down (for a second time) another inch and had all the cup removed from my props. With the fresh prop job and a clean bottom (they power washed the bottom while the props were being changed) I’m now burning:

2200 RPM (Port/Stbd): 12.3/14.2 gph
2400 RPM (Port/Stbd: 15.2/17.1 gph

(to save you from having to reference the chart, the 450 diamond curve is 13.6 gph at 2200 and 17.5 at 2400, the 480CE curve is 14.5 at 2200 and 19.0 at 2400)

Question is – is that close enough or do I need to keep going? I’ve now taken 2″ of pitch out and all of the cup. My prop guy doesn’t know if he can take any more out of these props. They are 4 blade nimbral and they started as 24×31 with a slight cup (i think he said #4) and are now down to 24×29 with no cup. Should I consider a completely different type of prop? 3-blade? Different radius?

Also, since both engines are well under the target curve at 2400 but one engine is slightly over at 2200, is it actually “easier” on the engines to run them at 2400 instead of 2200?

Quick recap – I bought the boat last November and have been trying to get the propping right ever since. I started with 24×31 inch props which were a little bent up. I had them re-conned and pitched down 1″ to 24×30 (scans are attached earlier in this thread). At that point I was burning:

[April 2018]
2200 RPM (Port/Stbd): 13.1/15.1 gph
2400 RPM (Port/Stbd: 16.3/18.1 gph

A few months later i had the after coolers replaced with new “seaboard style” coolers from this site and had all the raw water heat exchangers serviced. I measured fuel burn again, and, I suspect due to several months worth of bottom growth, saw the following numbers:

[June 2018]
2200 RPM (Port/Stbd): 14.6/17.1 gph
2400 RPM (Port/Stbd: 18.5/19.6 gph

That’s when I decided I was too far over the 13.6 @ 2200 RPM target and decided to pitch down again. The first time I pitched down, back in april, I lost hardly any speed at cruise. I attribute that to the fact that even though i removed pitch from the props, I also reconned them so they are more efficient. This time, when I removed an inch plus the cup, I lost about 3 kts of speed at cruise.

[Nicholas]

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Looking at your “Before” scans the port (LH) prop was a 1/2″ of avg. pitch lighter than starboard (RH). Then you had them matched as part of the recon. When you were running the “Before” props was the P & S data closer to one another?

Unfortunately I only have data from one engine before the re-prop. It’s a long story…when i first bought the boat the digital screens weren’t functional. I tried to have them repaired but they were too far gone. I ended up ordering a pair of gateways to translate the J17008 data to NMEA2000 so I could view the engine data on my MFD. But one of the two gateways was DOA. While I had just the good one hooked up and was waiting for a replacement for the other, I noted my fuel burn was above the recommended curve. I also was starting to see some soot accumulating on the transom. This was during my delivery of the boat from FL to the Chesapeake Bay and I still had several hundred miles left to go. I decided to go ahead and have the props pulled, reconditioned, and pitched down, even though I didn’t have data yet for one side.

I still think that was the smart thing to do, but it drives me crazy now not having a good before/after baseline for the discrepancy between the engines.

[Rob Schepis]

Nicholas Cummings wrote:

Question is – should I consider having the port engine prop pitched lower than the stbd to make up for the discrepancy between the engines? Or is that just asking for different problems?

Looking at your “Before” scans the port (LH) prop was a 1/2″ of avg. pitch lighter than starboard (RH). Then you had them matched as part of the recon. When you were running the “Before” props was the P & S data closer to one another?

[Nicholas]

Rob Schepis wrote:

So the EGT was 100% unchanged even when your other data recently went askew?

The EGT went up on one engine to about 900F when I had the problem with the split hose and broken hose clamp after the aftercooler job. Once I got everything tightened back up, the EGT returned to spec. I’m using the SMX dual engine pyrometer I got off this site – being an analog gauge it’s hard to say it’s 100% unchanged from before. But both engines are right around 700F now, or a hair under, which is what they were before the aftercooler job when I recorded the fuel burn numbers previously.

[Nicholas]

Thanks, I’d never noticed that tolerance on the spec sheet before. Makes me feel a little better.

I’ve removed the elbow to peek inside the turbo but wasn’t able to snap a photo because the elbow is so darn heavy and I was by myself. I did not see any evidence of water having got in. No corrosion, etc, and the bolts were fairly easy to remove.

I’ve attached the prop scans – before and after. And as I said before, just a month ago (after the prop job) I was at or below your recommendation for gph at cruise.

Perphaps the aftercooler replacement has nothing to do with it and, this being my first summer with the boat, is a natural increase in loading as barnacles start to accumulate on the prop shafts. If so, I suspect I’ll need to prop down again so that I’m still below the curve at the worst point of the season

Question is – should I consider having the port engine prop pitched lower than the stbd to make up for the discrepancy between the engines? Or is that just asking for different problems?

[Tony Athens]

Comparing Engine performance Numbers-Twin engine boat

Read the attachment a few times and think HARD.. This is from Cummins, not me as to engine performance tolerance.. This applies to EVERY DIESEL ENGINE Cummins makes, I’d guess it’s a universal engine tolerance spec for just about every diesel engine in this category……………………..+/- 5%, you are well within that spec.

Now add this to the equation…………….You are running around with 15+ year old 480CE’s, the first semi-electronic engine Cummins ever put in a boat.. Believe me, they left room for improvement………… Overall, I think you are chasing something that you won’t find.. As long as your fuel burn at cruise RPM’s in the 1900-2200 RPM range is where I said they need to be, you are good to go..

And last, remember this………….As the bottom and running gear fowl with any type of growth and with the addition of every POUND you add to the boat, the numbers you get will only go south as to what you would really like to see………….Just call it “BOATS”

P.S. Curious about a couple things:
1)When your props were done–Class 1 or better–Got scans?

2) Have I seen the inside of the exhaust outlet of your turbos?

Tony

[Rob Schepis]

So the EGT was 100% unchanged even when your other data recently went askew?

[Nicholas]

air leaks fixed, engine loading still higher than before changing the coolers

I think I’ve got all the air leaks sorted out. The turbos spin up more or less as they should. I still see a slight lag on the port side, but I can’t swear it wasn’t doing that before.

I’m still seeing higher engine loading than before. Quick recap – after buying the boat last fall I immediately set to work getting the propping correct per Tony’s recommendations. The engines weren’t horribly overloaded, but they were over the recommended fuel burn curve. After having the props reconned and pitched down, I got both engines down or below Tony’s recommendation. For some reason, even though the prop scans show they are matched perfectly, the port engine always seems to have about 10% higher fuel burn than the starboard, even at idle.

A few weeks ago, I had my tech pull the aftercoolers and the cores were shot. I ordered new ones from here. While he was at it, I had him service the heat exchangers and oil coolers, and also set the valve lash.

Once he got the new coolers and got everything installed, I had a few problems with busted hose clamps and cracked hoses that were causing air leaks. I think my tech got a little aggressive tightening the clamps. I got that sorted out.

Here’s the problem – after having this work done I went out and checked my engine loading and fuel burn rates again, and for some reason both engines are now higher, to the point where I’m over the desired fuel burn again.

I can’t imagine what would cause the engine loading to go up after pulling off NFG aftercoolers and replacing them with brand new ones. The only thing I can think of is that with the boat sitting for two or three weeks getting the work done the bottom growth built up. But the bottom job is only about 6 months old, and it feels a bit slimy in some places but I definitely don’t see any major growth on the bottom, barnacles on the running gear, etc.

Can anyone think of what might be causing the higher engine loading after having this work done? I’m not opposed to pulling the boat and propping down again, but it seems crazy since just a couple of months ago, before I had the work done, I was right where I wanted to be. Here are my before and after numbers. The “before” numbers were taken with full fuel and water, four people and a bunch of junk on board. The “after” numbers were taken with a quarter tank of gas and almost empty holding and water tanks, so if anything they should be lower.

Engine temps and EGT were in spec and the same for both engines. I have data at more RPMs, but just posting a few data points below:

2000 RPM
Port before: 12.6 gph, 16 psi boost, 57% engine load
Port after: 13.6 gph, 18 psi boost, 61% engine load

Stbd before: 10.6 gph, 14 psi boost, 45% engine load
Stbd after: 11.1 gph, 16 psi boost, 48% engine load

2100 RPM
Port before: 13.2 gph, 17 psi boost, 57% engine load
Port after: 14.9 gph, 21 psi boost, 65% engine load

Stbd before: 11.4 gph, 16 psi boost, 48% engine load
Stbd after: 13.0 gph, 19 psi boost, 55% engine load

2400 RPM
Port before: 18.0 gph, 27 psi boost, 72% engine load
Port after: 19.2 gph, 28 psi boost, 78% engine load

Stbd before: 16.3 gph, 24 psi boost, 64% engine load
Stbd after: 18.2 gph, 27 psi boost, 72% engine load

[Nicholas]

Will do. Thanks rob

[Rob Schepis]

I read this last night and just logged in to reply that you need to go over the charge air delivery piping/hoses on the port engine. Good to see you got that sorted out. If the starboard engine was making up for what the port engine was having trouble doing it will skew the numbers. Get the port engine air delivery 100% up to snuff and go for a another ride…

[Nicholas]

Ok I ran the boat today to get some more data. There is definitely something strange going on. Possibly more than one thing.

I measured my fuel burn about a month prior to getting the new aftercoolers.

At 2100 RPM, I was burning 13.2 gph on the port engine with 17psi boost. The stbd engine was burning 11.6 and 16 psi boost. EGT was around 700

Now, at 2100 RPM, I’m burning 15.6 gph on the port with only 14 psi boost, and on the stbd it’s 13.1 gph with 19 psi of boost. The port engine EGT is steady around 700 but the stbd is up around 900.

In addition, when I throttle up the port engine lags behind and has a harder time getting over the hump. Boost pressures seem to be consitently lower on the port side.

So to summarize- after having new aftercoolers installed, oil coolers and heat exchangers serviced, and valve lash set, my fuel burn on both engines has gone up 10-15% at cruise. My port engine is isn’t making as much boost and struggling to get over the hump while my my stbd engine EGT is about 200 degrees high.

I’d very much appreciate any advice…

Edit- I found the boost problem on the port engine. The hose going connecting the pipe coming out of the turbo and into the aftercooler was split. I suppose that could account for the fuel burn with the port engine trying to make RPM without full boost pressure.

But why would the stbd engine fuel burn be higher? And what could be causing the high EGT on the stbd engine?

[Nicholas]

Tony –

I’m well aware of where I need to be in terms of propping. I (regrettably) started a different thread on that topic here: https://www.sbmar.com/community/topic/480ce-overpropped-what-to-tell-prop-shop/page/2/

The upshot is that after having the props reconned and pitch taken out, I was at 14.1 gph on one engine and 13.4 on the other at 2200 RPM – which, the variation between the engines notwithstanding, is on or below fuel burn curve you recommend. I was also able to achieve rated rpm at well below 100% engine loading, though I realize that’s not the important factor for this engine. The cruise rpm fuel burn was what I used to get the propping right, as you recommend.

The problem is that now, just a couple of months after getting the propping right, I had the aftercoolers replaced (ordered from you), the heat exchangers and oil coolers serviced, and the valve lash set.

My old aftercoolers were in pretty rough shape and I thought if anything, putting on brand new aftercoolers would improve (reduce) my fuel burn. But it’s gone the other direction – I went from being right on the desired fuel burn curve to being over it again, and the only thing that changed was the new aftercoolers, valve lash, and servicing of the other raw water heat exchangers.

[Tony Athens]

480CE engine loading

If you want to see your 480CE last much longer, you need to throw out what you doing as to thinking you are propped OK.. WOT is not a good indicator for proper engine loading for this engine…….

Until you prop down to where your engine loads to 13.4 GPH at 2100 RPM, you are over propped with this engine…. Forget your WOT RPM or your load % numbers–Totally meaningless.. You will probably have to loose 2+ inches on pitch.

Tony

[Nicholas]

Engine loading higher now

Interesting…with the new coolers and the heat exchangers serviced the engine loading is now higher. I can still make 2675 rpm, but engine loading is now 98% and 100% with one person and half full tanks.. It was 89% and 96% before at WOT with a full load . Will run it more tomorrow and get some more data points.

[Rob Schepis]

Breeze CT clamps “nut-driver tight” —leave the 1/4” ratchet in the bag..

1 user thanked author for this post.

Nicholas

[Nicholas]

Yup. Busted clamp on turbo. Probably over tightened. Thanks!

[Rob Schepis]

Air leak from one of your air hose/tube connections not properly seated/tightened as part of the aftercooler install.

1 user thanked author for this post.

Nicholas

[Nicholas]

…also lots of black smoke when I try to throttle up on the stbd side

[Nicholas]

Help! No stbd boost after aftercooler install

Got the new aftercoolers from seaboard this week and had them installed. Had heat exchangers and oil coolers serviced at the same time. Just got the boat out to run it. Ran ok for a couple min at 2000 rpm. Then I tried to throttle up to 2200 and the stbd engine RPMs dropped off to 1800. Checked my guages and I’m not getting any boost on that side. Port side is fine, but maybe 2psi max on the port side. Won’t rev up past about 1800 rpm. No other signs of trouble. Temps, etc all ok. Any thoughts on what might be causing that after all the work we just did?

[Nicholas]

Well, the tech who did the work for me thought perhaps the cores hadn’t been removed, but cleaned some how in place. We were puzzled though because the damaged tube ends made it seem like someone had hammered the cores out. But Rob’s explanation of the zincs bouncing around damaging the tube ends might explain how that could have happened. So I guess my “forensic” theory would be that perhaps the cores hadn’t been removed in…? But they’d be “cleaned” in place. And the zincs pieces were what damaged the tube ends. But who knows. All we know for sure is that they weren’t taken care of properly.

What i hope is that I’ve caught it early enough to mitigate any damage to anything else. I guess time will tell, but I think I’m doing everything prudent on my end to enable the best outcome possible.

[Author]

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