Replacement diesel?

[FF]

Looking at a boat with a pair of DD 8.2 , not a good engine from years ago.

The engines are under the aft cockpit floor (V drive) SO should be pretty easy to swop.

Wondering if any modern medium truck diesels have been marinized ?

A pair of rebuilt 500ci Cummins would be first choice , but the height of the inline engines would require the cockpit to be rebuilt UGH!

The boat requires 220 shaft hp @20K ,, claimed burn 10.5 gph

27k is claimed @ 18.8gph , and only 72 hp for 10k, burn 4gph.

The 27K @ 18.8 gph might be about 10gph per engine which should be reasonable for a modern medium duty engine to produce.

10 to 15K would be sweet spot for our style of cruising , as long as the engine would accept our 10-12 hour days.

Any suggestions on modern engines of a V config?

 

[rslifkin]

How much height do you have to work with? Would the smaller (B series) Cummins 6cyl fit in there? Based on your power output needs, they should be capable of a good lifespan assuming you don't plan to cruise much over 20 kts.

Otherwise, take a look at the Yanmar 8LV. Not a ton of info out there on them, but they've been around for a few years at this point. 370hp V8, similar footprint to a gas big block and only about 1000 lbs. Based on the little bit of info I've seen and the published fuel burn numbers from Yanmar, they're very efficient (better than the Cummins QSB 5.9 or 6.7).

 

[Rufus]

How many hours on the 8.2's? What's wrong with them exactly? Lots of folks have had great experience with them as long as they have the big head bolts and haven't been constantly run on the pins as is typical in a sport fish. Is the boat a sportfish?

As you probably know there are some very attractive turbo V6 and V8 diesels in the current field of pickups...the Fords, and I believe the Dodge Rams (Fiat diesel for the V6) use an SAE bell housing. None marinized to my knowledge, but you might getaway with minimal heat shielding or use of heat extraction on the exhaust manifolds if they're located under the transom. Not sure about how far you'd have to go with emissions....maybe not at all if you do it in your back yard.

 

[Ski in NC]

The QSB 5.9 and 6.7 are at least a few inches less tall than the C series, they might fit. Maybe. The 8.2 is definitely shorter than most and if they built the deck to fit tight to the 8.2 there may be no room for a QSB.

20kt at 10.5gph (assuming total??) is pretty stellar economy. My light and skinny 38 with a single 450C does 20kt at 11gph, and I like to brag about it!! So a boat with two engines doing the same is pretty dang good.

Also the 8.2 does not have the greatest reputation, agreed, but most of that comes from boats where the engines have to work HARD and if they are overheated. With proper care and feeding and especially if they are run gently, they hold up ok.

 

[High Wire]

30ish+ year old engines that are still running can't be all bad. Are they running or is this a project boat?
Yanmar 4LHA 240 hp may fit but are light duty engines.

 

[tiltrider1]

I can’t imagine it being cost effective to repower an old boat. The Volvo D6 would fit. While Volvo gets a lot of bad press for replacement parts expense new D6’s won’t need any replacement parts for along time. The Duramax diesel has also been marinized but it probably makes the Volvo look cheap.

 

[Pete Meisinger]

Thirty year old engines must be in a thirty year old boat, right? Repowering with brand new engines will run you close to $75,000, probably more. Then you still have the thirty year old boat.

Unless the blocks have holes in them or sat underwater for a period of time I would look to rebuilding them.

pete

 

[jleonard]

Mercruiser 7.3 D-Tronic

https://www.ebay.com/itm/Mercruiser...ne-Long-Block-Boat-Engine-300hp-/172356369807

 

[ranger58sb]

Looking at a boat with a pair of DD 8.2 , not a good engine from years ago.

Wondering if it's worth it to bother swapping... at least at first...

The DD 8.2T doesn't get much love out there, but the one we had worked fine. Had the larger head bolts, after we did the J&T recall.. otherwise, stock as far as I can remember.

Maybe if you ID a suitable replacement, should it become necessary, do nothing else... just run the 8.2Ts until/unless replacement becomes mandatory?

-Chris

 

[Ken E.]

Even if you had to put some money in the 8.2's and replace some hang-on parts, you'd still be way ahead over a different engine re-power. These engines do get a lot of bad press, but I have two friends who have them and like them.

 

[Rufus]

The 8.2 got bad press from the trucking and bus community because of the early head bolt/gasket problem, and the fact that users didn't like spending the effort to keep the injector racks in adjustment. In a boat, the rack typically sits at one position most of the time, and are not an issue. The low fuel burn numbers quoted by the OP are characteristic of the "fuel pincher". A gem of an engine in my experience. When we bought our boat I found a low mileage truck engine for a spare, and stocked up on rebuild parts. Everything is still sitting in the garage 15 year later. The only thing I've done to those engines is change oil, filters, and belts. Now, the 300 horse intercooled version typically installed in small sportfish boats was pushed beyond it's limit from the outset.

 

[sunchaser]

Why not gassers? Fuel costs will not be an issue for the foreseeable future. A pair of V8s would provide the dimensions you seek and be lighter too.

 

[FF]

Gas engines would be OK with me the boat is an inshore boat not a voyager so less range would not be a big deal.

The hassle is gas engines require spark proof everything in the engine space , haven't itemized the list to guesstimate a cost. Yet,

The best suggestion so far would seem to be the Mercruiser 7.3L diesel, if there still made .

The boat is a 44 ft Midnight Lace .

My dream boat for 20 years , so if not now when?

The current plan would be to operate the boat at modest speeds and do next to nothing except plenty of PM .

I am looking for a plan B should the engines die early in our ownership.

To a great extent the boat would replace our Sprinter class C to snowbird every year from CT to Fl and back in the spring.

 

[rslifkin]

With the amount of stuff that would need to be re-done, swapping to gas probably wouldn't make sense. Yes, the engines would be cheaper, but there would be far more to do than bolting in a different set of diesels, I'd think.

I'd say the biggest thing is to measure the available space for engines and also get a ballpark weight for the current setup. That'll rule out some options as either too big a weight change or just won't fit. Then you'll have a smaller, easier to choose from list. With engines all the way aft, a huge weight change is likely a bad idea.

 

[smitty477]

Midnight lace 44 ....

https://www.cheoyleeassociation.com/Power/PowerMLace.htm

 

[jleonard]

The best suggestion so far would seem to be the Mercruiser 7.3L diesel, if there still made .

That's why I posted the link to ones for sale on ebay.

 

[rslifkin]

Also, thinking about it, if those fuel burn numbers are correct for total burn, that's an incredibly efficient hull. Looks like it's pretty light, with an estimated loaded weight of 17,500 lbs. The 20 kts and 27 kts fuel burn numbers are just about half of what I estimated for my own (admittedly heavier) hull with modern diesels.

If there's ever been a boat for going fast in the 40+ foot range that's not a super stripped down express cruiser, this seems like it considering that the fuel burn penalty is really not bad for high speeds.

 

[Pete Meisinger]

On my first read through on your issue I guess I missed that you have a "V" drive installation.

Changing from D.D.s to almost any other brand will probably mean changing the "V" drives as well as everything else including mounts, shafts, transmissions, props, etc.

My original estimate of $75,000 just doubled. The numbers and cost just plain don't support an engine swap. Don't even consider it.

pete

 

[smitty477]

Also, thinking about it, if those fuel burn numbers are correct for total burn, that's an incredibly efficient hull. Looks like it's pretty light, with an estimated loaded weight of 17,500 lbs. The 20 kts and 27 kts fuel burn numbers are just about half of what I estimated for my own (admittedly heavier) hull with modern diesels.

If there's ever been a boat for going fast in the 40+ foot range that's not a super stripped down express cruiser, this seems like it considering that the fuel burn penalty is really not bad for high speeds.

I believe the fuel burn numbers come from the link I posted above with Renault engines, that link also has comments on the hull design.
From link....
"To keep the interior free of clutter, Fexas decided to put the engine well aft, under the cockpit - another reason for the high-buoyancy stern sections. The engines - Renault RC 210 DTS diesels, with 2:1 reduction through V-drive units, turning (ideally) 22x23 props - were expected to be more than adequate.
Representatives from Renault tested the boat's performance and were completely satisfied at the results, calling the test,"...a tribute to the design of the bottom of this yacht." Renault's figures boiled down to the following: Fuel consumption: 18.8 gph at 27 knots, 10.5 gph at 20 knots, and 4 gph at 10 knots. Fuel: 200 gal, range at cruise: 380 nm. Cruising Displacement: 17,500 lb."

 

[Baker]

Midnight lace 44 ....

https://www.cheoyleeassociation.com/Power/PowerMLace.htm

There is one of those for sale in my marina!!!!

 

[DavidM]

I am with Rufus above- keep the DD 8.2s. In addition to the injector rack problem he mentioned and the need to swop out the head bolts for better ones, there is also a fix to the coolant system that includes a vent from the aft cylinders to avoid a pocket of air building up and blocking coolant flow.

If you do these mods, I don't see why those engines can't keep producing 200 hp each for a long, long time.

Pretty boat though. Keep your money for new engines and spend it on keeping the cosmetics sparkling.

David

 

[rslifkin]

If you do these mods, I don't see why those engines can't keep producing 200 hp each for a long, long time.

Even better than that, I'm under the impression from what FF posted and the other link that was given that a 20 kt cruise is about 200-ish hp total, not per engine. Based on the numbers for the Renault powered boat, it was doing 27 kts at less than WOT with 420 total HP. So cruising at 20 kts is going to be very easy on the 8.2s with only somewhere in the 100 - 120 hp per engine ballpark for continuous power demand.

 

[Lepke]

The Ford 7.3 turbo diesel (designed & built by International) was marinized and there are rebuilt engines out there. But it has several electronic sensors that are a pain. Marine accessories like exhaust manifold could be hard to come by. Newer Ford diesels are nothing but trouble. Especially the 6.0.

The Dodge diesel would be too tall. No idea on the GM.
If cost is an issue, there are marine diesels from China. Some Cummings are made there. And parts of many other diesels are made there.

 

[FF]

"Changing from D.D.s to almost any other brand will probably mean changing the "V" drives as well as everything else including mounts, shafts, transmissions"

Now you have me stumped . The V drives I have seen were mounted to hull stringers to take the thrust and the engine was a distance away with a short shaft to the V drive.

I would hope to keep all that intact and simply have the machine shop create a plate to the DD tranny. A new shaft is no big deal. Re use filters and exhaust .I don't suffer Bestitis (any more).

The more modern engine would be almost the same power , so the V drives and tranny should be OK.

New motor mounts is also no big deal , controls should come with the engine , if not Murphy Gauges would monitor the engines.

The biggest problem I see is all the new engines have electronic injection , nice and quiet if they do it right , but perhaps Sea Tow in lightning capital FL.

All the more modern engines spin at a higher RPM , which might demand a different tranny , or a different set of props.

A marine exhaust manifold for a converted engine could be avoided with a dry stack exhaust.

Yes , unquestionably keeping the stock DD 's would be best , and a 10-12K cruise would be just fine with us .

I'm trying to figure worst case ,just in case, as I don't want to end up too broke.

 

[Mrwesson]

If you're talking new.. Well you shouldn't be talking new engines.

You can buy modern engines used, freshen them up before install and save yourself tons of money. Big diesels don't trade hands often on craigslist and other regular sources. My advice would be be calling places in Ft Lauderdale once you decide on a engine. They are the yacht capital of the world and always have lightly used engines laying around.

You can get more HP in a much smaller package but i'm not sure how that'd work out for you. The 5.9 Cummins QSB engines are putting out up to 480hp. I occasionally see them for 10k for a pair but typical is about 20k and new is about 20k per engine.

 

[rslifkin]

If the transmissions are an integrated trans / v-drive there might be fitment issues. But I don't think it would be anything un-solvable.

It looks like the 8.2s turn anywhere from 2800 to 3200 RPM depending on rating, so plenty of other engines would be in the same ballpark. And there are enough marinized diesels out there that at least one of them of sufficient power will fit into the holes the 8.2s are in now. Looks like the 8.2s are 31.4 inches tall, so depending on how much space you've got above them, you likely have choices. A QSB 5.9 is 33.8 inches tall, for example, so only an extra 2.5 inches. The newer Yanmar V8 diesels are just over 30 inches tall, so they'd definitely fit.

Looks like the Detroits are just over 1500 lbs, so the QSB or Yanmars would be lighter.

From what I can find, the 8.2s in marine form were rated anywhere from 130 to 300hp, depending on who marinized them and turbo or not. I'm seeing mentions of Detroit calling the turbo versions continuous rated at 160 or 200hp at 2800 RPM. NA continuous ratings were 130, 145, or 160hp at 2800. So I wouldn't worry about cruising at 20 kts with the 8.2s if the total power demand is only in the 110hp per engine ballpark at that speed. Doing that for days on end wouldn't be pushing them too hard, IMO. I'd personally consider that to be standard fast cruise with the ability to sprint a bit faster.

 

[Pete Meisinger]

Dear F.F.

If you are looking for advice here it is. Don't do it!

If you have never attempted it don't say something is simple. Motor Mounts, simple? (Not) , Dry exhaust, simple? (Not) Wiring, gauges, fuel delivery, adapter plates, longer or shorter shafts, etc, Simple? (NO, NO, NO)

Have fun, Good Luck, you will need it

pete

 

[bluebyu]

FF ran a marina for many years.
He is very savy. Motor mounts would be easy for one of his knowledge.

 

[Rufus]

If the 8.2 engines check out on survey, they will run for decades at low to medium power levels. Just pay close attention to the cooling system. The ones in our OA have a factory installed coolant temperature sensor on the engine that sounds an alarm at 205 F. I added thermocouples/alarms after the exhaust risers. Also, water temperature at high power settings dropped almost 10*F after I cleaned out the calcium deposits in the transmission coolers.

Back in 2005 Johnson and Towers sent me an excellent prop chart for the engines in our boat. Matched up very closely to real world values when I checked them against actuals. FF, if J&T did the marinization on the subject boat, you might give them a call to see if they have one for a boat like the one you're considering. I spoke with one of the engineers who actually worked on the marinization/certification of the 8.2 back in the day. His view was that it was a marginal truck engine, but made a great marine conversion. A "gem" to use his word. By the way, the engine uses the truck/street governor...takes a little familiarization, but fine in actual use.

 

[Arc]

Swapping out a V drive boat is a can of worms. A set of QSB’s [ that would be a good choice} will cost 100k. 70 k for factory rebuilds. Now the fun starts, gear engine beds, props, wiring, check tanks while you are there, paint bilge, change out all hose and thru hulls. Here we go. $150 easy