Re-Power 48 Californian

[knotheadcharters]

Alright here goes. I have a 1989 48 Carver Californian with DD 6-71TI's. They have a little over a thousand hours on them and run perfect. I usually run 8-10 knots but open them up for a few minutes every four hours or so. Now the issue at 8-10 they burn very little fuel approx. 3-5 gallons an hour each. Yes I know to some on this forum that is a tremendous burn rate and there lies the issue. When I was boat shopping I really wanted a pair of 120hp Lehmans or something along those lines. I was wondering the feasability of yanking the DD's and putting in a couple of low hp diesels. I am trying to maximize fuel range as I would like to retire in a year or so and do some extended cruising. Just a thought and wanted to get some feedback from others.

Thanks.

 

[THD]

You certainly don't need your current HP to get 10 knots. At 58' and close to 50 tons, we get a max of 10+knots with twin JD 158 hp. I would take a close look at the JD engines. They are very reliable and very efficient. Also, very good service.

 

[knotheadcharters]

Yes John Deere would be on the short list.

 

[Woodsong]

Only 1,000 hours and running great with no issues? You would only be saving maybe 3-4 gallons per hour. I think if you got quotes for the total repower, as well as factoring in the "while we're at it" additions that would be done, I think you'd probably be better off waiting til your DD's give up the ghost.

 

[ksanders]

Only 1,000 hours and running great with no issues? You would only be saving maybe 3-4 gallons per hour. I think if you got quotes for the total repower, as well as factoring in the "while we're at it" additions that would be done, I think you'd probably be better off waiting til your DD's give up the ghost.

I was going to say just that.

The 671 is probably the most widely used diesel in the world. Parts are everywhere as are people that know how to work on them.

I just went through a repower. You're going to drop 50K+ probably more like $60K on the repower.

That buys allot of gas

 

[ben2go]

If he resales his current set up,then he could recoup 1/3 to 1/4.Maybe he could do a swap with someone wanting more power and gain a few coins since he would be down grading,so to speak.

 

[Marin]

Something to consider when repowering with a smaller, less powerful engine and that is weight.

Case in point---- When we bought our old GB in 1998 the GB dealer in Bellingham was commisioning a brand new GB52 that someone had bought and was going to put into their charter fleet. The buyer had specificed smaller than standard engines. I don't know his reasoning but he did.

The immediate problem they were dealing with was that it was found that the with these smaller, lighter engines, the boat did not trim per design. This was manifested most obviously in the water that puddled on the side decks well forward of the drains where it would have puddled had the engines been the weight the boat was designed for.

So a lot of warranty time was spent by the dealer's shipwright (who was also doing jobs on our boat which is how we found out about this) to totally rework the deck drain system so the water wouldn't puddle in the wrong place.

Granted, these kinds of problems can sometimes be fixed with ballast, but in this case the owner didn't want to do that.

While the desire to get rid of a fuel-hungry engine is certainly understandable these days, the question becomes is it really cost-effective in the long run? A boat that is or is going to be cruised extensively for a good portion of the year may recoup the cost of the repower in fuel saved. But a boat that isn't going to be a full or near full-time cruiser may very well not.

I agree with KSanders---- the cost of the repower could buy a hell of a lot of fuel for the existing engines. It should be a fairly simple math excercise to figure out if the fuel saved by the repower will repay the cost of the re-engine.

I've never run a boat with 6-71s but I've been around them and from everything I've learned there's not much out there that can beat them in terms of reliability and longevity. So unless the fuel numbers really make the case for a repower, or unless one is really tired of the noise, it may well be a case of trying to fix something that's not broken.

 

[knotheadcharters]

All good valid points. The cost of the repower could buy alot of fuel. I do plan on living and cruising six months a year. The ballast is reasonable too due to the fact that those engines weight about 3 grand a piece give or take a few pounds so it could cause a stability issue. I do think that the DD's will probably outlast me as long as I take care of them and I do I do not run them hard at all. I keep them at operating temp and change the oil and coolent as specified. I just like reading about 1 and 1.5 gallons an hour instead of 1 gallon a mile. Aw well fuel is cheaper than a repower.

 

[Edelweiss]

I was going to say just that.

The 671 is probably the most widely used diesel in the world. Parts are everywhere as are people that know how to work on them.

I just went through a repower. You're going to drop 50K+ probably more like $60K on the repower.

That buys allot of gas

________________________________

I was going to say that too!!

Also keep in mind that you may have to swap out more than just the engines. Engine gauges, controls, and a 6-71 is going to swing larger props and shafts, maybe have to change out the shaft and struts as well? I don't think you will ever recover your investment. Unless there is some other issue with the DD's, I don't see any value in a repower at this point?

Plus 5 or 6 gallons per hours would be very typical fuel burn for a 48' trawler with twins at 10 knots. That's a little less than what my neighbor burns with his 52' Jefferson with twins at 10 knots and about the same as my twin 130 HP Perkins at 10 knots. At 6 GPH you're doing just fine and you should appreciate having the extra power and speed available for when you need it.

Larry B

 

[expat]

One of the fire trucks in our fire hall has a DD engine.I looked at it when doing equipment check last week and it has 15000 yes thousand hours on it and I know it has never had any major work, it runs either flat out against the govenor or at idle, it comes out of a heated hall but goes from full cld to WOT in about 1/2 mile. pretty much indestructable in my opinion.

 

[psneeld]

All good valid points. The cost of the repower could buy alot of fuel. I do plan on living and cruising six months a year. The ballast is reasonable too due to the fact that those engines weight about 3 grand a piece give or take a few pounds so it could cause a stability issue. I do think that the DD's will probably outlast me as long as I take care of them and I do I do not run them hard at all. I keep them at operating temp and change the oil and coolent as specified. I just like reading about 1 and 1.5 gallons an hour instead of 1 gallon a mile. Aw well fuel is cheaper than a repower.

You'll have to do the math to see if you'll recoup the money...which even on a tight budget will take a LONG time unless you are burning 500 plus gallons, maybe even 1000 gallons a year.

The stories of 1.5 gallons per hour for your size boats are doubtfull...unless you are willing to run 5-6 knots.

Your boat with twins, even small ones are gonna burn 2-3 gallon an hour to push your boat at 8-10 knots. Slow it back 2 knots and the fuel burn will drop considerably.

I would first start by looking at fuel burn curves of your engines and some different sized engines that you might consider.

If you truly think fuel burn could pay off in the long run...especially if you keep the repower costs down...you could look around for the 80 or so hp diesels that power generators/light towers for construction companies. My boss has picked up dozens of these at auction for a song...you just have to figure out how to marinize them and get them into you particular boat. ballasting may be important...but is pretty easy to do once the install is complete and you see what you might need to do.

 

[knotheadcharters]

More than likely I'll stick with the Detroits. They are great engines and have a long track record. I'm back in Afghanistan working an when I'm not flying I sit around and dream up stuff to do to the boat.

Now on another note does anyone have Flowscans? That would be a way to maximize my fuel burn. Last time I checked they were about 1300 bucks per engine but that might be more cost effective than a repower.

 

[Portuguese]

...To say the least, I wish I had access to rebuild 6-71 in Brazil. Rainha Jannota would have appreciated an engine like that....oh yeah!

...floscans are only good until you learn about your engines drinking rate. After that you don't need anymore...I am sure that you'll learn that rate as quick without spending extra $1300...that money buys a lot of gallons of fuel

 

[ksanders]

More than likely I'll stick with the Detroits. They are great engines and have a long track record. I'm back in Afghanistan working an when I'm not flying I sit around and dream up stuff to do to the boat.

Now on another note does anyone have Flowscans? That would be a way to maximize my fuel burn. Last time I checked they were about 1300 bucks per engine but that might be more cost effective than a repower.

Floscans are an invaluable tool. with them you will be able to tell your fuel burn at any speed.

After you know your fuel burn vs rpm curve, you can use them for maintenance. Here's a good example:

Once I noticed a sharp increase in fuel burn while out on a cruise. Checking the engine revealed a cracked return line from one of the injectors. Diesel was spraying on my hot engine!

 

[FF]

"I think you'd probably be better off waiting til your DD's give up the ghost."

Another 10,000 -15,000 hours may take a long time.

An engine swop will never pay, however when its time to rebuild the injectors there ARE other choices that may knock off some fuel burn.

The DD handbook will give some choices.

The Flow master suggestion is excellent .

You might install a set of prop locks to hold one shaft , and operate on a single engine, after getting underway.

More complex , but if you have HYD on the boat, is a small hyd motor to power the unused shaft , just to the trail, no drag speed.

Best use for Flow Scans I saw was the use of the total fuel burn feature.

When a capt in Block Island was handed the fuel bill, he knew the pumps were "fixed".

Gave them the choice between the State Inspectors and free fuel .

Guess which choice they took!

Never caught a crook , but since the sheen police go crazy over a table spoon of oil , it sure is nice to KNOW ! how much will be required , ans go slow for the last 2-3 gal.

FF

 

[FlyWright]

Never caught a crook , but since the sheen police go crazy over a table spoon of oil , it sure is nice to KNOW ! how much will be required , ans go slow for the last 2-3 gal.
FF

I've heard several stories from folks who have detected fuel leaks through their FloScan units before it became a larger problem. SeaHorse found a problem on the FloScan twice before confirming it on his video camera system.

Here are 2 items I have onboard to avoid fuel spill problems while refueling. They are inexpensive and work as advertised.

Fuel Fill Warning Whistle & No Spill Fuel Saver - YouTube

 

[FF]

ON Most 71 series DD the most common problem is a broken "jumper strut" .

This is the tubing that connects the injector , and if cracked (more likely over tightened) it will add fuel to the sump. CARRY SPARES!

Check the oil level on shut down , and if your DD seems to "make oil" don't call the patent office , pull the valve cover and take a look.

The DD hand pump recommended months ago is perfect if you wish to pressurize the system, to it works well as a priming pump too.

When you are at the DD shop get the proper timing pin , required should you ever need to pull an injector.

 

[knotheadcharters]

Thanks FF I am new to diesel and have been learning as much as I can about the 71's. Boatdiesel has been a great help.

 

[FF]

Perhaps someone there has the power/rpm chart for your engine down rated with smaller injectors.

Injectors come from 40 -135 for many engines , perhaps yours would be happy with the smaller units.

The goal on a DD is to size the injectors so the engine is running at 60% or harder at the RPM you cruise at.

60% of rated power at max hp , or better will get most DD up in the 16 HP/gal range, about the best you can do.

Big hassle is this still may be too fast for the hull to be driven cheaply (SLx1.15)

Then all you can do is accept the poorer fuel efficiency at slow RPM ,
but enjoy the quiet and wait another 15,000 hours.

Many 6-71 (non turboed) are run at 1200RPM as prime gen sets , if you can get well loaded at that low RPM , you will be waiting till at least 20,000 , perhaps 30,000 shows on the clock.

Too bad CPP are so hard to retrofit.

There is always a set of cruising props , to get efficiency , but then you need an EGT to keep from overloading and a different pip on the tach for max RPM.

 

[knotheadcharters]

Thanks again FF. Any knowledge I can garner about my motors is appreciated. I do believe I am over proped by 2 inches as I run up to 2050 rpms on both. I had a DD mechanic do a compression test and ride along in the engine room for the sea trial when I had the boat surveyed. I wish I would have asked him which injectors I have. At what rpm due the turbos kick in? I have been running the boat between 1000 and 1200 rpms for a speed of 8 to 9.5 kts depending on tides. When I get home I am going to search out a DD guru to completely go through the motors and get everything right.

 

[FF]

At what rpm due the turbos kick in?

I would install a gauge , far more accurate than some guesstimate.

same for the injectors DA Book will be the guide for downrating the Hp .

 

[markpierce]

Some railroads downgrade the diesel engines on their older locomotives when shifting from road to less-demanding switching duties. The object is to reduce engine maintenance costs. Downgrading includes removal of turbos and perhaps some other engine adjustments. Could such a tactic be worthwhile on higher-performance marine diesel engines?