Repowering - Cummins or Yanmar Engines

[rhyoung]

Hi Everyone,
We have a 1984 55-ft Lin Hwa Trawler; Full displacement; 78,000 LBS; that we absolutely love. Its time to re-power. The original 185 hp twin Perkins have no more life left in them, gears are equally worn out. A couple of different mechanics have looked at them, including the local Perkins dealer, and all recommended replacing as they are not even candidates for rebuilding. Given that Perkins stop making parts for its motors relatively quickly after the model is produced we are not interested in pursing Perkins motors. We are looking at equivalent 250 BHP engines from Cummins and Yanmar. For Cummins its the QSB6.7 (not sure why Cummins 4 cylinder motor is not being recommended by the boat yard) and we are exploring twin Yanmar's 4LV 250 HP motors on our own before we get back to our boat yard to have more discussions with them. Our top speed is 8Kts but usually try to stay around 4 to 6. Any thoughts on 4 cylinder motors for our size boat and Yanmar versus Cummins? Thank you in advanced.

 

[Bacchus]

I'm not familiar with the 4 cyl version of either. I do have a single Yanmar 6LYA STP in our Mainship 34HT and have had a Cummins 6.7 in a motorhome. Both work(ed) well for me and I believe Both are respected and tested diesel engines. I believe there were a few well documented issues with specific models of both 6 cyl... not sure about 4s.
Generally parts were readily available for both.

 

[kapnd]

You may be able to retain your prop, transmission and running gear if you use a Cummins 6BT@ 180 or 210 hp.
The Yanmar revs higher to make the hp, so the whole drivetrain will likely be wrong.

 

[Comodave]

Back in the day the 4 cylinder Cummins were not balanced so they shook a lot at idle and low speed. Ok in a wood boat but not necessarily in a glass boat. As far as which engine to put in a trawler hands down the Cummins. It is a lower reving engine and probably heavier built than the Yanmar. The Yanmar is more for a planing hull where weight is an issue. Cummins used to sell remans that had a warranty just like the new ones. But you will have to install them within Cummins specs to make the warranty good. I would contact Tony Athens at sbmar.com. He is a Cummins repower guru.

 

[O C Diver]

It is my understanding that Cat bought Perkins. Buddy of my services forklifts. He refers to the cat engine in some of their forklifts as "Perk a pillars".

First, I would check with Trans Atlantic Diesel about rebuilding what you have. If your engines were original to the boat (40 years old), served you and previous owners well, and were a good match, why spend 3 or 4 times the money.

Regarding the transmissions, are the clutches tired or are reduction gears torn up. If the transmission can't be rebuilt, you may be able to buy rebuilt ones from TAD.

TAD has a great reputation and usually rebuildable engines.

Trans Atlantic Diesels | Perkins Diesel Engines | Perkins Engine Parts | Cummins Diesel Engines

Buy Perkins Marine Diesel Engines and Perkins Engine Parts at Trans Atlantic Diesels

www.tadiesels.com

If TAD can't rebuild or doesn't recommend rebuilding your engine consider the below following.

Pause: I repowered the trawler in my avatar doing most of the work myself. So I have some experience.

If you repower the boat with significantly more HP you will likey have to change the propeller shafts, propellers, shaft through hulls, struts, and stuffing boxes to handle the additional HP. Remember, if you want a warranty, the engines need to turn rated RPM which usually means full HP at seatrial. Pushing 250 HP through 185 HP drive train isn't a recipe for success!

Next, unlike rebuilding what you have, assume the engine beds will need to be rebuilt. Most likely your exhaust systems from the engines back will need to be replaced, completely if increasing HP.

If reducing HP (as I did), you may be able to reuse the shafts and everything else associated with them. In my case, I reused the transmission, shaft, stern bearing and stuffing box (needed to change the propeller). So while I did rebuild the engine bed, the transmission had to be in the same place for the drive train to line up.

My buddy who did all the Fiberglass and paint work in his building, also does repowers occasionally. He is less expensive than some but knows the market well. Depending on the install, you can easily exceed the engine and transmission cost with the install!

If you do repower, try to go same or smaller HP and reuse shafts, shaft through hulls, struts, and stuffing boxes.

Ted

 

[rhyoung]

You may be able to retain your prop, transmission and running gear if you use a Cummins 6BT@ 180 or 210 hp.
The Yanmar revs higher to make the hp, so the whole drivetrain will likely be wrong.

I am concerned we may have to replace the entire drivetrain. I don't want to price myself out doing the repower.

 

[rhyoung]

You may be able to retain your prop, transmission and running gear if you use a Cummins 6BT@ 180 or 210 hp.
The Yanmar revs higher to make the hp, so the whole drivetrain will likely be wrong.

Back in the day the 4 cylinder Cummins were not balanced so they shook a lot at idle and low speed. Ok in a wood boat but not necessarily in a glass boat. As far as which engine to put in a trawler hands down the Cummins. It is a lower reving engine and probably heavier built than the Yanmar. The Yanmar is more for a planing hull where weight is an issue. Cummins used to sell remans that had a warranty just like the new ones. But you will have to install them within Cummins specs to make the warranty good. I would contact Tony Athens at sbmar.com. He is a Cummins repower guru.

I have not looked at remans. My assumption has been it might be easier to sell with new sometime over the next 5+ years

 

[rhyoung]

It is my understanding that Cat bought Perkins. Buddy of my services forklifts. He refers to the cat engine in some of their forklifts as "Perk a pillars".

First, I would check with Trans Atlantic Diesel about rebuilding what you have. If your engines were original to the boat (40 years old), served you and previous owners well, and were a good match, why spend 3 or 4 times the money.

Regarding the transmissions, are the clutches tired or are reduction gears torn up. If the transmission can't be rebuilt, you may be able to buy rebuilt ones from TAD.

TAD has a great reputation and usually rebuildable engines.

Trans Atlantic Diesels | Perkins Diesel Engines | Perkins Engine Parts | Cummins Diesel Engines

Buy Perkins Marine Diesel Engines and Perkins Engine Parts at Trans Atlantic Diesels

www.tadiesels.com

If TAD can't rebuild or doesn't recommend rebuilding your engine consider the below following.

Pause: I repowered the trawler in my avatar doing most of the work myself. So I have some experience.

If you repower the boat with significantly more HP you will likey have to change the propeller shafts, propellers, shaft through hulls, struts, and stuffing boxes to handle the additional HP. Remember, if you want a warranty, the engines need to turn rated RPM which usually means full HP at seatrial. Pushing 250 HP through 185 HP drive train isn't a recipe for success!

Next, unlike rebuilding what you have, assume the engine beds will need to be rebuilt. Most likely your exhaust systems from the engines back will need to be replaced, completely if increasing HP.

If reducing HP (as I did), you may be able to reuse the shafts and everything else associated with them. In my case, I reused the transmission, shaft, stern bearing and stuffing box (needed to change the propeller). So while I did rebuild the engine bed, the transmission had to be in the same place for the drive train to line up.

My buddy who did all the Fiberglass and paint work in his building, also does repowers occasionally. He is less expensive than some but knows the market well. Depending on the install, you can easily exceed the engine and transmission cost with the install!

If you do repower, try to go same or smaller HP and reuse shafts, shaft through hulls, struts, and stuffing boxes.

Ted

Our trawler always felt under powered. I am concerned that 250 may be too much and RPM's are definitely a concern. Perhaps 210 may be better. If I can reuse my props, shafts, etc.. that would be a plus. I will reach out to TAD on Monday. Thank you.

 

[rhyoung]

You may be able to retain your prop, transmission and running gear if you use a Cummins 6BT@ 180 or 210 hp.
The Yanmar revs higher to make the hp, so the whole drivetrain will likely be wrong.

Good advice, I will look into this. Thank you!

 

[O C Diver]

Our trawler always felt under powered. I am concerned that 250 may be too much and RPM's are definitely a concern. Perhaps 210 may be better. If I can reuse my props, shafts, etc.. that would be a plus. I will reach out to TAD on Monday. Thank you.

The factory remain engine from Cummins is a 6BT at 220 HP. It's a new engine with one used part mechanically injected and no after cooler.

Ted

 

[Diep]

I don't think low-hour re-manufactured Cummins 6BTs would do you any harm at all on resale in a '84 boat.

I like our 6BTs and they are simple and pretty easy to service. I would definitely look into them before automatically going newer and higher HP, especially if there are knock-on effects causing the re-power cost to spiral.

 

[Insequent]

For a re-power you could also look at John Deere engines. Either a 4 or a 6 cylinder. To get over 200HP from the 4 it is turbo plus aftercooler. With the six you get 200, or a little more, without the aftercooler. I would price both the Cummins 6BT and the JD 6068's. My guess is that the 6BT's will be the most cost-effective, it will depend on how sharp the pencil is at your local dealer. Similar HP, likely similar additional work to install and both lower rpm than the Yanmar.

I put in a pair of JD 6068's at 201HP each in 2012, max 2600rpm. Very happy with them. They replaced a pair of Cummins V8's which made 270HP at 3000rpm. I was able to keep shafts/props, did not even need to change prop pitch.

 

[BruceK]

The Cummins 210 is turbo but not aftercooled, excellent engines imo. But if you could rebuild the Perkins, so no changes required to mounts, exhausts, instrumentation, fuel supply, etc. it is a far cheaper process, I`d suggest exploring that to the full.
IMHO,the Cummins 4cyl is not as smooth running as the 6. The Yanmars rev higher and servicing may cost more than Cummins, and make sure you can get a safe install for introducing water to the exhaust so there is no risk of back flow to the turbo.

 

[Xlantic]

I replaced my GM 220 HP V8s with rebuilt Cummins 5.9 6B 120 HP and new Twin Disc gears, keeping the props.

My boat displaces 27 metric tons.

I have not noticed any difference in power but then I don't exceed 8 knots.

There are on-line calculators you can use to see if you can keep the current props as they are.

 

[Gdavid]

For Cummins its the QSB6.7 (not sure why Cummins 4 cylinder motor is not being recommended by the boat yard) and we are exploring twin Yanmar's 4LV 250 HP motors on our own before we get back to our boat yard to have more discussions with them. Our top speed is 8Kts but usually try to stay around 4 to 6. Any thoughts on 4 cylinder motors for our size boat and Yanmar versus Cummins? Thank you in advanced.

My best guess why the yards are recommending 6-cylinder engines for your boat, in spite of your modest power requirements is based on the size of your boat and its running gear. While a modern 4-cylinder diesel can put out the power you need, the torque curve at low rpms may not be suited to your heavy boat and existing running gear. I'm assuming your current transmission is around a 2:1 ratio, you would probably need a 3:1 ratio transmission and now you are going to be running significantly higher cruise engine speeds which may be less pleasant.

A 6bt is very similar in dimensions to a perkins T6.354 and use the same bell housing pattern, so they were very common replacements. The velvet drive transmissions that most perkins are pair with (in US markets at least) are very compact and allow for about as small of powerplant footprint in the engine room. Other transmissions may require the engine to be mounted higher, which may interfere with the deck height, or they may be longer or wider. While the block size of the modern cummins b series is very close to the older engines, all of the accessories are pretty bulky, resulting in a pretty large footprint. You may not have the height or width required without making some modifications to your engine room.

I'm intimately familiar with the T6.354 engines and they are pretty good old powerplants. Parts and support are limited, and this definitely impacts the sale of any boats with them. That said, with some forethought, research and TAD, I've been able to get everything I've ever needed for mine, and mine is one of the contra-rotation versions, which complicates several aspects. I'm on my 5th season with my boat, and while it has always started smooth and ran well, it carried low oil pressure that just continued to get worse. I raised the engine in the boat and dropped the pan to find a damaged crank and main bearings. I had the crank machined and put it all back together for less than $1K in parts, but I spent many hours of my time which would have been quite expensive in mechanic's labor.

If you love your boat, and return on investment is not a concern, I would go with the remanufactured 6bt's as a straightforward and similarly performing engine. I was too cheap to go this route even at half of your expense (mine is a single). If you aren't comfortable putting more into the boat than you are likely to be able to sell it for, I would consider used perkins or talk to TAD about having them rebuilt. They are a sleaved engine and unless there are corrosion issues, they are relatively inexpensive to repair.

Are yours the range 4 version with the integrated exhaust manifold-multicoolers?

 

[Baker]

Not only in my opinion, but in others on this thread, the Cummins 6BT is the winner here. Super simple. American made. Parts easy to come by and cheaper than Yanmar. And the aftermarket for Cummins is more robust….meaning you can buy the same part without the Cummins part number on it and cut the price in half(all the hang on stuff). Y’all mars also have a tendency to make their power in the higher rev range so you might be running a higher RPM for the same amount of power. I will reiterate. The Cummins 6BT is a slam dunk for this application.

 

[Gdavid]

Not only in my opinion, but in others on this thread, the Cummins 6BT is the winner here. Super simple. American made. Parts easy to come by and cheaper than Yanmar. And the aftermarket for Cummins is more robust….meaning you can buy the same part without the Cummins part number on it and cut the price in half(all the hang on stuff). Y’all mars also have a tendency to make their power in the higher rev range so you might be running a higher RPM for the same amount of power. I will reiterate. The Cummins 6BT is a slam dunk for this application.

This degree of consensus seems impossible, we must change the subject to anchor design or something more contentious.

 

[Ken E.]

Late to the party but I repowered 10 years ago with Cummins 6bt 5.9's, 210 hp new factory remans, mechanically controlled. New engine warranty, much cheaper than new engines. On a scale of 10 for liking them, I'd say 12. Also put in new Twin Disc gears, also satisfied there.

You should run a prop calculator app to check your existing props against whatever engine you decide on and various gear reductions. Boatdiesel.com had one of these but others are available.

 

[Greg QS]

My vote Cummins . Lower rpm engine will last longer than the yanmar.

 

[Comodave]

With 78K pounds I would always go with the big slow turning engine rather than a lightweight high speed engine. With that weight there is something to be said for larger displacement engines.

 

[lwarden]

This might be of interest. Pair of 210 6BT with 3,600 hours. $26K with Twin Disc 2.5:1 transmissions.

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[Jeff F]

This degree of consensus seems impossible, we must change the subject to anchor design or something more contentious.

Ok, just to keep the conversation alive, I'd recommend checking into the Beta 115. Or a pair of reman 4bt 150(?) HP. Put big reduction gearing on.

OP, what's your maximum cruise speed/rpm/fuel burn?

Nothing wrong with the 6bt, but you might be happy with smaller engines and have significant $$ left over. Ted listed the reasons.

 

[sean9c]

I'd chose a Deere 4045 over a 4bt any day.

 

[Jeff F]

I'd chose a Deere 4045 over a 4bt any day.

Sure. Maybe they offer remans. No need for more than 135 HP IMO and remans are allowed for repowers.

 

[Comodave]

If you want a 4 cylinder engine then I would not want the Cummins in a glass boat. I have run an ex Navy tender with the 4 BT in it and it was fairly rough at idle. The last time I checked, a long time ago, the 4BT wasn’t a balanced engine. I was looking to repower a trawler and spoke at length to Tony Athens about it. His recommendation was not in a glass boat but in a woody probably ok since the wood would absorb some of the vibration. Ted, OC Diver, had a John Deere 4 cylinder in his boat and had good experience with it. I believe it is a balanced engine.

Although if I were doing this I would go with the 6BT remans. Having the larger engines with that big of a boat would just feel better to me.

 

[Diep]

OP is starting out with 370 installed HP and looking at putting in 500. Most folks are recommending 420.

Even if 230-270HP makes sense, the number of people who understand that is small. I think a 55 footer with that kind of HP would struggle at resale which was a concern for OP.

 

[rhyoung]

Hi Everyone,
We have a 1984 55-ft Lin Hwa Trawler; Full displacement; 78,000 LBS; that we absolutely love. Its time to re-power. The original 185 hp twin Perkins have no more life left in them, gears are equally worn out. A couple of different mechanics have looked at them, including the local Perkins dealer, and all recommended replacing as they are not even candidates for rebuilding. Given that Perkins stop making parts for its motors relatively quickly after the model is produced we are not interested in pursing Perkins motors. We are looking at equivalent 250 BHP engines from Cummins and Yanmar. For Cummins its the QSB6.7 (not sure why Cummins 4 cylinder motor is not being recommended by the boat yard) and we are exploring twin Yanmar's 4LV 250 HP motors on our own before we get back to our boat yard to have more discussions with them. Our top speed is 8Kts but usually try to stay around 4 to 6. Any thoughts on 4 cylinder motors for our size boat and Yanmar versus Cummins? Thank you in advanced.

Hi all,
After careful consideration we are going with the cummins 6BT 5.9 210 HP. Thank you all for your thoughtful responses as they were very helpful!
Much appreciated,
Rob

 

[Comodave]

Good choice.

 

[Capt Pappy]

Very informative post for us that are not quite there yet, but hope to soon

Seen a few vessels for sale that reference fairly recent install of the cummins 6BT 5.9 210 HP
and now understand why

 

[Hobbit]

Hi all,
After careful consideration we are going with the cummins 6BT 5.9 210 HP. Thank you all for your thoughtful responses as they were very helpful!
Much appreciated,
Rob

Good choice. I've used these engines in our excavating machinery and they are bullet proof....and they don't vibrate. Our boat has a single 215 Hp Cat D333 that gives us 7.5 kts at 4 US gals/hr boat is 94000 lbs.
Good Luck.