R25 engine choices

[TimOb]

Hi All,
I almost hitched onto Mac's dingy thread with this, but decided it would be best to start a new one.

I'm wondering what the differences in fuel economy and performance characteristics would be on the R25 with the 75 yanmar compared to the 110. An r25 with the 75 hasn't been built, so it's just theory at this point. The engines are nearly identical except for hp and torque. With the 75, you'll need to run a smaller prop to get the rpms. RangerJeff thinks it'll get better fuel economy, but I'm wondering if that's true because typically, with the 75, you'll need to run at higher rpm (with the smaller prop) to get the same speeds as the 110.

Here's some numbers I came up with from the Yanmar specs:

110 - 2300rpm - 40hp - 200lb-ft - 2.1gal/hr
75 - 2300rpm - 27hp - 150lb-ft - 1.5gal/hr

110 - 2600rpm - 60hp - 190lb-ft - 3gal/hr
75 - 2600rpm - 40hp - 140lb-ft - 2.2gal/hr

110 - 2800rpm - 71hp - 190lb-ft - 4 gal/hr
75 - 2800rpm - 48hp - 135lb-ft - 2.8gal/hr

110 - 3000rpm - 90hp - 185lb-ft - 4.7gal/hr
75 - 3000rpm - 61hp - 128lb-ft - 3.5gal/hr

110 - 3200rpm - 108hp - 175lb-ft - 5.8gal/hr
75 - 3200rpm - 72hp - 102lb-ft - 4.5gal/hr

Thoughts?

Thanks,
Tim

[Doryman]

Les (when he was a Ranger dealer) told me that the original 75 was replaced because it did not deliver the performance that the factory advertised would come from the boat, before the first hull was splashed. If I remember right, he told me it was underpowered and inefficient. If you don't get satisfactory answers here you might give him a call and see what he has to say.

Warren

[thataway]

Fuel consumption comes from the "work" the engine is doing. If both engines are doing the same work, they will use the same amount of fuel assuming that the internal friction etc is the same.
I don't think you will have to drop the prop pitch too much, (you won't drop the diameter and go to a "smaller prop"--you want the effeciency of the largest prop you can swing,) especially if you are planning to run at displacement speeds--which I assume that you are. I would suppect that most of the boats are running at dispacement speed (less than 7 knots) 80% or more of the time. One of the differences between the two engines is the amount of max torque, both of which reach this at about 2000 RPM. But the 75 hp is about 180 ft lbs and the 110 is about 200 ft lbs. Not a big difference.

You will see slightly better economy, but it is much more related into the speed at which you drive the boat. If you keep both engines down to 1.2 x sq rt LWL, or about 5.7 knots you will get very good economy--no matter which engine. If you go to 7 knots you are beyond 1.5 x sq rt LWL and the boat rapidly becomes less effecient.

You won't be able to run at the semi displacement speeds of 11 knots, but this is ineffecient, and you probably will not want to do that anyway. We ran 85 hp in a 60,000 lb boat with an LOA of 62 feet and still got 9 knots.
So 75 hp is plenty for any head winds or seas you will get into. However, I would stay with the stock engine, because of resale and the occasional time you want to run at 10 knots.

[starcrafttom]

This is what turned us off from the tug in the first place. I mean that we really loved the looks and the room of the tug, but 8 knots is just to slow to get any where. I would die of bordom and never have enough time to get any where in the short amount of time I have to go boating. 20 mph is bad enough but I have learned to live with it. I the tug got the speed as advertized ( 14 to 16 knots at the show when first released?) then the extra room and nicer ride are worth the loss in speed. No at 8 knot you can buy bigger boats at lower cost and get almost the same milage. its to bad the tug is not the fast trawler it was advertized as, I really like the looks and the room.

[Island Ranger]

From what I understand, the 75, 90 and 110 are the same engine. The 75 is naturally asperated, the 90 is turbo charged and the 110 is turbo charged and intercooled.

I wonder if the 75 will get the boat up on a plane - I believe our 110 had some degree of trouble when the boat was loaded. We ran at the recommended 80% power, 2800-2900 rpm and got 10 kts (11.5 mph). Any lower rpm and we would really slow down (not planing as well) and not save much on fuel. At WOT, the boat feels like it is planing much better - running 12 - 13 kts (13.8-15.0 mph). But, you aren't supposed to run at WOT for more than 5 minutes per operating hour.

I think we have two speeds to choose - either 70-80% power, the recommended operating range and go 10-11 kts (11.5-12.6 mph), or run at 1700 rpm and get 6.5 kts (7.5 mph with a heck of a lot better fuel economy). The Yanmar manual says NOT to run the boat slowly during breakin (first 50 hours) and if you do - be sure to rev it up periodically.

If you would be happy at hull speed (6.5) - the 75 might be a better choice since it would be loaded more while running at the low speed - better for the engine I think.

Mac
Mac

[captd]

Bob,
Maybe you can figure it out. I have a friend in Panama City who has a 27 ft lobster boat. He repowered with a 240 horse Yanmar. (Turboed) He burns 5 gal per hour at a cruising speed of 25 miles per hour. It is an old boat with lots of fiberglass. I have gone out with him several times and never see him put in as much fuel as I did with twin 40 's on the 22 ft C-Dory doing the same trip. It is a true planing hull, which is probably the biggest reason

Point of interest: he has the boat up for sale and it won't sell. He has come down to the price of the new engine and it still don't sell. Never get your money out of repowering an old boat.
Captd

[thataway]

The 45 hp 4JH4AE is the Natural aspirated engine. The 4JH4-TE is 75 hp and turboed. The 4JH4-HTE is the 110 hp engine, which has more turbo boost and aftercooled. (not sure about the after cooling on the TE model)
All are the same basic block.

The 75 hp would not plane the C Ranger 25. Just not enough HP. If you get good mileage at 7 knots--try 5 knots, you will do even better. If you only want to do 5 to 7 knots, go with the 45 hp NA engine. It will last longer. The 110 is almost 1 HP per cubic inch (127 cu inch displacement)--and at 1 hp / cu inch you start having longivity problems. True highly turboed engines need to be run up every hour or so under load. But they need to cool down after this also.

Captd, the 27 foot lobster boat sounds like one a friend of mine used to own. When they had it there was a 6 cyl Ford Lehman in it and it would plane. The Yanmar is a lighter and high hp engine. At 5 gallons an hour he is using 100 hp. Of course it often takes less hp to keep a boat on a plane than to get the boat on a plane. Sounds like a nice boat. Do you have a reference on the sale? I might have a friend who is interested.

[TimOb]

As always, thanks all!

My comments from Mac's last post:

"From what I understand, the 75, 90 and 110 are the same engine. The 75 is naturally asperated, the 90 is turbo charged and the 110 is turbo charged and intercooled."

re:the 75 is turbo charged.

"We ran at the recommended 80% power, 2800-2900 rpm and got 10 kts (11.5 mph). Any lower rpm and we would really slow down (not planing as well) and not save much on fuel."

re: Is this a Yanmar recommendation, or is it just for this "type" of engine. Also, did you ever run around 1700-1800rpm for an extended period? If so, can you comment on it?

"The Yanmar manual says NOT to run the boat slowly during breakin (first 50 hours) and if you do - be sure to rev it up periodically."

re: This seems to agree with Bob's comments on running a turbo charged engine up at least every hour or so. Exactly what does this mean though? Go up to WOT, but for how long? Spose it's not rocket science here - bring it up to WOT until the rpms max and then ease off (?). Question is though, is this an ongoing procedure, or just during break-in.

"If you would be happy at hull speed (6.5) - the 75 might be a better choice since it would be loaded more while running at the low speed - better for the engine I think."

re: hmm. Do you think lower loads and internal pressure might actually be bad for the engine to the point of reducing longevity? Can there be some kind of mechanical backlash effect going on that can cause more wear or something. Backlash is kind of a

My comments from Bob's posts:

"The 75 hp would not plane the C Ranger 25. Just not enough HP. If you get good mileage at 7 knots--try 5 knots, you will do even better. If you only want to do 5 to 7 knots, go with the 45 hp NA engine. It will last longer. The 110 is almost 1 HP per cubic inch (127 cu inch displacement)--and at 1 hp / cu inch you start having longivity problems. True highly turboed engines need to be run up every hour or so under load. But they need to cool down after this also."

Nice paragraph, Bob. Thanks! Regarding the durability issue though. We are talking about diesel blocks and components. I understand your point when comparing the 45, 75 and 110. Compared to a gas engine of similar power ratings, assuming both engines equally maintained, the 110 turbo diesel is still going to get a lot more hours, no? I'd be surprised if I put 2000 hours on it in 10 years (hopefully, I'm way low on that).... My question is, how many hours (on avg) should one expect from these engines before a rebuild?

"So 75 hp is plenty for any head winds or seas you will get into. However, I would stay with the stock engine, because of resale and the occasional time you want to run at 10 knots."

for me, that statement probably sums it up, which means I'm leaning toward the 110.

Thanks again,
Tim

[thataway]

The Rev up on turboed engines applies thru the engine's life, not just break in. At Break in I like to run any engine at low speeds for the first hour or two--but with occasionall run up to 50% of wot. As time goes on, then increase the amount and time of rev up and by 5 hours up to cruiisng RPM Regularly. (which would mean planing speed).

As for the amount of run up. I don't go to WOT in diesels often. I do run my outboards up to WOT each time I go out--but just for a min or two.
I like to go to at least 85% of WOT for the run up on a turbo diesel. NA--not necessary, but you don' like to vary the speed to some degree.

Longivity. One of my friends is Robert Smith who owns American Diesel, who was the importer of Ford Lehmans, and a Perkin's distributer. He had most of the trawler market covered. We talked one night about expected longivity of the small high speed Yanmars vs the Ford Lehmans, which generally go 10,000 hours before an overhaul--sometimes 20,000 hours. His feeling is that we will see many more at 2000 hours with the Yanmars. I also noted that many of the few years old Hinkley picnic boats were being repowered--they all have the highly turboed Yanmars.

So with good maintance a highly turboed engine should get at least 2000 hours--and quite likely more than that. Outboards used to be good for 1000 to 15000 hours--some of the new ones 4 strokes are getting over 10,000 hours in commercial use (every day running). Truck gas engines--marinized usually are good for about 2000 hours. Running The engines conservatively will increase the longivity--but keep an eye on the turbos..

But--most boat engines die from the lack of use, rather than too much use!

[Island Ranger]

Sorry I don't have my Yanmar manual home with me, but it specifies the break in speeds - and it pointedly says do not run the engine slowly at this time (first 50 hours). They say something like "now is not the time for a slow leasurely cruise" (during break in).

I do not know much about diesel engines - only what I've read recently (and from the manual) and I thought that they are designed to run loaded (70-80% of max power). Running slower apparently builds up deposits - and that needs to be burnt out or the engine will start smoking. You are supposed to be able to tell the "health" of the engine by the color (and amount) of the exhaust.

I was theorizing that the 75 hp version was a better choice 'cause you have keep it loaded more often if you were choosing to cruise at 6 kts or so.

During our trip, we cruised for two tankfuls at 6.5 kts - partially 'cause we wanted to see what our mileage would be, partially 'cause I wanted to feel what it would be like, and partially 'cause there weren't any fuel stops around so we needed the extra range. I loved it - mostly had the autopilot steering while we watched the world go by. We could do just about anything while underway - cooking, reading, crafts (when you were off watch). Those things are more difficult at 10 kts. But it sure was nice to be able to bump it up to 13 kts to run Malibu rapids 30 minutes before slack (current was still over 3 kts!). From what I can tell, the engine did fine. I did speed up periodically to keep the deposits from building up.

I'm glad I got the 110 version. We have 350 hours - and plan to take it in for service on Thursday.



Mac

[Old Dog]

The service manual that came with my 110 Yanmar recommended a slow break-in much like that described by Thataway.

However, there is a service bulletin out by Yanmar that contradicts the manual. It strongly recommends that the engine not be babied during the first 50 hours and provides some good technical reasons why that is a very bad idea for these engines. It specifies keeping the idle and low RPM time to a minimum in the first 50 hours and running at varying, but reasonably high RPM's and occassionally WOT for up to two mnutes. Quite a difference in procedures.

I would suspect that the Yanmar manual is out of date. Given that about 25% of the manual is cautions and warnings (did you know that if you dropped the Yanmar engine on your foot, that a possible injury could result?), it's likely that getting a change through their lawyers takes years.

Unless you get a different manual than I did, be sure you get a copy of the bulletin on break-in from the factory.

We only have about 90 hours on ours at this point. Typically cruise about 8.5 knots. Averaging 2.2 gallons per hour so far. Like this engine.

[thataway]

At 2.2 gallons an hour you are only using about 44 hp. The old addage still holds fairly close for the new dieselsl--20 hp per hour per gallon.

[Old Dog]

Interesting, but possibily about right. Assuming straight line fuel consumption (not likely), that would be about 4.4 gallons an hour at cruise speed. With idle time and time spent below cruise, something over two gallons an hour doesn't seem too unreasonable given no long cruises to date. Thanks for the confirmation.

Had a 220 HP Volvo diesel in a boat for a number of years that ran at about the same speeds. Kept very good records of fuel purchases and found that it used 4.5 gallons per hour on average through several hundred engine hours of use. Which seems consistent.

[thataway]

The only way to know exact fuel consumption at a single point in time is to have a calibrated fuel flow meter. This is much easier on the outboards because there is no fuel return line as in the diesels. (Diesel is used to cool and lubricate the injection pump and injectors, this is returned to the tanks). The flow meter has to have two transducers, one at a low flow level for the return, which makes the system considerably more expensive. Flowscan is one of the standard units. Navman started to build a diesel unit, but I believe that got lost in the buying and selling of the company. On the outboards it makes considerable difference in fuel economy in relitatively small amounts of trim. Displacement diesel boats are not as sensative, but the planing types are.

There is one other way, and that is to have a "day tank" or a small tank which is easily calibrated. This way you can accurately measure the fuel used in intervals of time when you have constant speed.

Just saying that one uses 2 gallons an hour can be rather missleading--as I believe you are pointing out--because a lot of time is at slow speeds, docking, and in congested areas. The more open water running you do from fill up to fill up at a constant speed, the more accurate the "consumption" will be. In our ocean crossing boats, we might start a journey and spend a few minutes at idle, hoisting anchor etc--but then there might be days when the diesel engine was at a constant RPM and speed. With that one could get a quite accurate determination of fuel consumption--and miles per gallon--which is really more important than gallons an hour.

The fuel consumption per HP is a constant. The fuel consumption per boat speed may not be, because of current, wind, waves, trim etc.

[thataway]

A couple of other comments about running diesel's at low speed and longivity. I had a 9 KW generator which I put about 4000 hours on, but my very good friend put 25,000 hours on the same model generator. This genset used the same engine which is used in the very common 3 cyl sail boat engine which is rated at 28 hp, and will turn up 3600 RPM--in fact some genset makers will used a smaller engine and run it at 3600, instead of 1800 (1500 for 50 hz power). Of course these engines are not turboed. But they are run at a constant speed of 1500 to 1800 RPM from the time they are first started, until they are taken out of service. My friend did valve jobs on his engine at about 10,000 and 20,000 hours (this represents a couple of circumnavigations and many years of living board on the hook). When he finally got a new generator, we torn down the engine prior to selling it. The cylinder walls were clean, no ridge or carbon deposits. The engine could most likely run another 10,000 or more hours--but new bearings, connecting rods and pistons were put in, after the cyl were honed and it was put into a sailboat--where it will probably only last a few thousand hours more.

Also the some of the ferries on the Calif. Delta run their engines 24 hours a day (at least used to--not sure if there are still any ferries) for two years (about 17500 hours) at 1200 RPM without stopping or varying the speed. The oil is refined and added to while they are running. They have never had a failure. (These run an azmuth type of drive, in the center, so that the boat does not change direction--the drive does--and when at the "dock" bow in, the prop is pushing the boat against the dock--to leave, the drive is turned 180 degrees for the trip back across the channel.

The important issue is that all of these engines are operating under load. The marine diesel has to come up to temp and stay at temp. The varying speed at breakin is to prevent ridging on the cyliner walls. When the manuals say avoid prolong idle, this means at very low speeds not under load. Avoid low speed idling with no load. Generally the WOT is only for a brief time and only after the engine is warmed up. Until the engine is warmed up, avoid going above 3/4 speed RPM. Also be cautious about lugging a diesel during break in peroids (or any time for that matter).