Total and Reserve Power

Hi Tom,
That's true that the vast majority of us have boats w engines (still running) and don't NEED to know how to power load a FD boat. And on top of that only 5% or so actually have FD boats. I partake in and contribute to threads that I have no need for information or problem solving material. Most of what we do here is just talk about things related to trawlering and learn things and about things we normally pass up. Most probably from threads and posts revealing things about backing into a slip or warming up our engines ect. There's many different ways of doing many things. Reading and talking about such things keeps me posting. Never thought I'd make 10,000 posts .... can't belive I have really. But I have. So if you wonder what this old guy thinks just ask me .. you may find out.

Opps ...?
I thought I was on the old guy thread.

While I'm not looking for the minimum engine possible with a boat, I do question that approach. I've always felt that you turn to the builder. You look at the engine manufacturers they recommend and have experience working with. They then either recommend an ideal solution based on experience or a minimum accepted. Then you select their ideal or you go one size larger than their minimum.

While I haven't read or attempted to digest all the technical information in this thread, I am just always comfortable having a little reserve. It may help with conditions to be faced on rare occasions. It may allow you to reach the minimum speed for a canal. It may mean that decades from now after the engine has aged it still is adequate, just no longer has the reserve. My way of looking at it isn't the science, which I'll let others figure out, it's also not a rule of thumb because I don't like rules of thumb. I've found they often don't apply across the board. No, it's simply a comfort matter. And I do like to feel comfortable in the decisions I make.

Here's something that some might find interesting...

The following are the specs given for my George Buehler designed Diesel Duck (Note: The part that I find interesting is that George is calculating about 41 horsepower to drive this Duck at its sweet spot of 8.53 knots. With this in mind, Seahorse Marine, with the blessing of George B., has called for a JD 4045 which produces 125HP. Doing the math, that's only 1.41 HP/1000 lbs or for you long ton folks that's just a hair over 3 HP per long ton).

I'd also like to point out that at 1.41 HP/1000 lbs it has less HP than the Nordhavn 43 and 46 which have 1.75 HP/1000 lbs which is the least amount of HP/1000 lbs than the rest of the Nordy fleet.

LOA: 53'
LWL: 50' 6"
Beam: 15' 1"
Beam WL: 15' 2"
Draft: 6'
Displacement: 88,402 lb.

Projected Speed and HP requirements, FLAT CALM conditions:

V/L ...Knots ... HP
1 ...... 7.11 .... 16.7
1.1 ... 7.82 ... 25.7
1.15 .. 8.17 ... 31.5
1.2 .... 8.53 ... 40.9
1.25 .. 8.88 ... 54.8
1.3 .... 9.24 ... 74.3
1.35 .. 9.59 ... 105

RATIOS:
Length to Beam: 3.56 D/L: 306

COEFFICIENTS:
Prismatic 0.691
Block: 0.325
Midships: 0.470
Waterline 0.806

Displacement and Weight Required for Various Loadings from DWL

Displacement at DWL = 88,908 lb.
At 3" below DWL loading needs 9365 lb; displ = 98,273 lb
At 4" needs 12,397 lb; displ = 101,300 lb
At 5" needs 15,663 lb; displ = 104,571 lb
At 6" needs 18,860 lb; displ = 107,768 lb

sunchaser said:

Eric, my point is quite simple. With but rare exception we all own a boat that has a given engine. No matter what the perfect theory is, few of us are going to yank out a perfectly good engine and install a smaller one to save a few dollars in fuel per year.

OC Diver is that rare exception. Kevin Saunders another, but less for saving fuel bucks and more for gaining entry to the 21st century. I'm sure there are a few others. Would those guys please raise their hands?.

...snip.....

Click to expand...

I'll raise my hand. Mk 1's usually came with a pair of Lehman 120's or the Cummins 555 (270 or 320 HP). Some had Cat 3208's, but not many. I repowered with JD 6068 in 201HP version. So right in the middle of the minimum and optional power choices from the builder.

It wasn't so much about saving fuel. The 555's were not as efficient as JD's for sure, and the difference was large enough that LA-Hawaii was not feasible with the 555's but would be possible with the JD's. And I was contemplating that because at the time the cost of freighting the boat to Australia was over $100,000.

The engine change arose as I had to replace leaking fuel tanks, and to do that I had to pull the 555's. I looked at going over them while they were out - new hoses and various other PM but stopping short of stripping them down. Afterall, they started first turn, made WOT and didn't smoke. And had only done 1900 hours. So why not put them back in? Well, two reasons. One was that the 'external' PM for both engines would equal the bare cost of one new JD factoring in parts and labour. Two, parts for the 555 are expensive, can be hard to get or need to be aftermarket. That might be OK in USA but I did not want to be waiting long times and paying 'Volvo' part prices when in Australia. If I put them back in without doing any PM I might get a few seasons without needing to do much, or I might not.

The choice of HP for my new JD's was based on experience running the boat. I knew that to cruise around 8-9 kn only needed +/- 150 HP. The Mk 1's fitted with Lehmans were in a sweet spot really, provided you were happy at displacement speeds in a SD hull. I also knew that the 270 HP versions of the 555 would get me to 16kn. But at 34 gph, with trim tabs down and ploughing a hole in the water that created a fearsome wake. Not really semi-planing, a bit short of that it seemed to me. In other words, running at a better SD speed needed more HP. Probably a total of around 800, maybe more. I thought about that, but only briefly. I would rarely be able to justify the fuel burn of semi-planing speeds compared to getting out of bed a bit earlier!

It was near the end of 2012 when I was ordering. Form Jan 2013 JD were only allowed to supply Tier 3 engines. Cleaner than Tier 2 certainly, but not as fuel efficient. For Tier 2, the dealer could readily get 300 HP versions of the 6068, and was willing to supply them at the same price as the 201 HP I wanted.

But I stuck to my guns and they managed to obtain a pair of the last Tier 2 201's to be sold. I did not want aftercoolers (on the 300 HP but not the 201 HP) and I had calculated that the 201's at 2600 rpm WOT were on the same prop curve as the 555's, 270 HP at 3000rpm. That turned out to be the case. We did not even have to adjust the prop pitch! Whereas, putting in the 300 HP versions (at 2600 rpm WOT) may well have necessitated new props.

I run the 201's at 35-50% load for 8-10kn speeds. Wind and waves do have quite an impact on loading level.

I could go on, but hell this post is already too long. Tom, be careful about asking folks to put their hands up.....

Brian,
That's what happened to us. One bad fuel tank and moving to Alaska. Didn't picture us very well off in the wild and considerably remote places w a 40 yr old engine. Willard had the power right (36hp) but I spent a lot of time convincing myself it was right. It all worked out perfectly and I'm still happy.
Most trawlers don't have the power right and some here may be faced w a power choice. Researching that question reveals a lot of things worth learning whether or not a power change is contemplated.

Brian

Sorry I forgot about your great conversion and detailed information you provided then and to this day. As you and OC Diver did, bringing these vessels back to life in a top notch way is worth knowing about for all of us faint hearted souls.

Question, any issues with the 6068 electronic engine controls?

Diesel Duck said:

...
The following are the specs given for my George Buehler designed Diesel Duck (Note: The part that I find interesting is that George is calculating about 41 horsepower to drive this Duck at its sweet spot of 8.53 knots.
[/B]

Click to expand...

I've noted that normally-aspirated JD's are no longer offered in Seahorse boats in favor of compressed air. Suspect this is due to government-requirements. Glad I've got the 4-cylinder JD NA version. Don't need the complication or added power.

BandB,
Most here seem to like extra power. And there's no "sin" to having it .. it's the boat owners money and decision. But any extra power does cost money and only justified if it's used .. IMO.

sunchaser said:

Brian

Sorry I forgot about your great conversion and detailed information you provided then and to this day. As you and OC Diver did, bringing these vessels back to life in a top notch way is worth knowing about for all of us faint hearted souls.

Question, any issues with the 6068 electronic engine controls?

Click to expand...

No issues with engine controls. But then I retained the morse gear and 'throttle' controls, even though the ones on the FB are a PITA to get the engine rpm in sync. Full electronic controls would have allowed sync, but I stopped short of that, and adding a joystick control as that would have entailed new gearboxes.

markpierce said:

I've noted that normally-aspirated JD's are no longer offered in Seahorse boats in favor of compressed air. Suspect this is due to government-requirements. Glad I've got the 4-cylinder JD NA version. Don't need the complication or added power.

Click to expand...

I don't see a normally aspirated JD engine that is EPA Tier 3 compliant. All of the JD engines seem to be turbo charged to meet the EPA requirements.

Later,
Dan

My understanding is that for Europe or USA, new boat builds require Tier 3 for the boat to be registered. Re-power of old boats has more flexibility.

You can get naturally aspirated JD's in Australia, designation 4045D, 6068D etc. Probably Tier 0 ! None of your damned EPA stuff forced upon us yet ! Mark must have just scraped through time-wise when the Coot was built. He could not legally do it now.

For Mako, Tier 3 has to be the way to go. But listen to Ski !

Insequent said:

...Mark must have just scraped through time-wise when the Coot was built. He could not legally do it now.

...

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The turbo version of the engine was an option at the time of purchase, but the naturally-aspired version I selected provides quite enough power for the boat, thank you.

markpierce said:

The turbo version of the engine was an option at the time of purchase, but the naturally-aspired version I selected provides quite enough power for the boat, thank you.

Click to expand...

Understood.

My point was that these days you would be obliged to have a Tier 3 turbo, like it or not. Either you bought the Coot before the new regs came into force, or it was not compliant but nobody checked at time of importation.

We had discussed emissions standards more on http://www.trawlerforum.com/forums/s3/old-engine-new-trawler-15857.html. My research on pretty much any available engine was that all the T3 engines are common rail with turbo and intercooler, electronically controlled of course. Non of the mechanical or naturally aspirated engines would meet the T3 rating.

I did however have conversations with Gardner and they were looking into adding some sort of catalytics to their old engines in order to meet modern standards. I don't know if they were ever successful, but they are an expensive option anyway.

makobuilders said:

Ski - I've sent a request to technical support to find out if the engine is fitted with twin counter rotating balance shafts or something similar.

Click to expand...

Here is the answer

"Non of the mechanical or naturally aspirated engines would meet the T3 rating."

Customer refusals have some of the engine mfg rethinking upgrading to Tier 3 some pure mechanical, non turbo engines.

Repairable , reliable may see the light of day again!

FF said:

Customer refusals have some of the engine mfg rethinking upgrading to Tier 3 some pure mechanical, non turbo engines.

Repairable , reliable may see the light of day again!

Click to expand...

Not a chance. Heard the same thing about automobiles a few decades ago. Look how good they are now. Cat, Cummins, MTU etc have far too much invested after being forced to adopt Tier 3. The big guys are not going to lobby EU or US governments for a roll back to satisfy a very small audience.

Specific to this thread, Mako's AGCO company choice builds tens of thousands of emissions compliant engines annually. There is a diesel engine world beyond a few US boaters that has set a course and is moving forward.

So if I'm going to repower Willy I'm going to need to find a 37hp turbocharged, common rail, intercooled and electronicly controlled engine? Surley not. It would cost four times as much as I paid for my new Mitsu in 06. There must be a power cut-off so small engines can be cost effective. How would on replace an old Onan generator engine?

Rebuild Eric, that is why we have our non compliant engines and will not give them up.

My first contribution to this interesting thread.

I'm with Ski overall.
One thing that hasn't been mentioned directly is Duty cycle of the engine.
It's OK thinking the engine can produce X bhp at Y rpm, the question is, for how long?
In a FD marine application the engine will need to produce this at a much higher duty cycle than in an automotive application. This is the main reason why a power reserve is needed in a marine application.
Working at 80% duty cycle seems way too high for my liking.
For any kind of acceptable life out of the engine my gut feel is you don't want the engine working any higher than 70% load for long periods. Ideally between 50-70% I would say. That's load, rather than revs, although of course the two are related.
In short, I'm sure your smaller engine will give its 80%, but it may only last less than 5 years. Stressing it less it will last longer, although diesels do like to be worked. In my view that's why many vessels are over powered.

FWIW my 33ft FD boat weighs about 7 long tons. It has 2x 62bhp na VP diesels.
I worked out that's 17.4hp per ton! Slightly higher than some of the figures quoted above! But the engines are only rated as light duty, so that may partly explain it.

Trundlebug - What you say makes sense, but I asked the manufacturer about estimated time between overhauls (assuming normal maintenance routine) and at what continuous rpm duty cycle. Here is what they had to say:

Hello,
1. I would say that best rpm range considering fuel consumption and lifetime for this engine is 1400-2000rpm
2. We have seen hours up to 30000h without major overhaul for this engine family, with medium duty usage and good service. With good fuel and maintenance, 15000 hours should be no problem even with higher duty cycle.

I don't know how this engine compares against Deere or other similar brands, but it is basically a marine commercial engine, not really marketed to the recreational boaters. Perhaps that has something to do with the solid record of AGCO.

Mako,

That's good news. Having read through all the thread postings I was concerned that duty cycle hadn't been directly mentioned and thought it should be considered every bit as important as power & rpm.
Glad you've got it covered and the response is detailed and encouraging.

I agree Trundlebug!
Fifty to 70% load should produce a long engine life.
And probably 80% load would shorten it a small amount like 5%?
But what would engine life be if run at 25 to 35%?
And to cut all corners what engine load would provide the longest life?

Mako- Good news on the balancer. I still would prefer a six for idle smoothness and to get cruise rpm and load lower, but that is your call.

Regarding CPP on your earlier post, I really LOVE CPP, but on your project I think it would be of minimal benefit. Aside from purchase cost, it has other costs down the road. If you pick an engine right and prop it right with a fixed wheel, you can optimize for hull speed and anything below that will be fine. Above hull speed sounds like a no go zone, and it would be with a CPP also, just that while hogging along you could load the engine properly. But what is the point in that.

manyboats said:

So if I'm going to repower Willy I'm going to need to find a 37hp turbocharged, common rail, intercooled and electronicly controlled engine? Surley not. It would cost four times as much as I paid for my new Mitsu in 06. There must be a power cut-off so small engines can be cost effective. How would on replace an old Onan generator engine?

Click to expand...

I'm not a student of the epa rules, but as I understand it, small engines are rated differently and still can be bought as mechanicals. I don't know the break point. Marine gennies are still mechanical. I think.

Thanks for the feedback everyone. As I think about it, there is an advantage to running the engine at 80% load. Assuming the boat is floating somewhere near DWL then the prop will be almost loaded to its design and be relatively efficient.

I'm intrigued about this Brunton's Autoprop H62 since it will mount to a standard shaft. The Southeast Asian dealer is working up a quotation for me. An extra 10-15% fuel savings could work out well in the long run, especially on a 60 ton boat that barely gets 1 nmpg.

Regarding manyboats' comment, I had discussions with the EPA legal team and since your boat would be a repower then you would not have to abide by latest tier, only us guys dumb enough to be building new boats. Give it another year or so, and Tier 4 will be here - can't imagine how sucky that will be.

Your duty cycle comments are spot on except that some commercial engines are rated at full load 24/7. Typically they are down rated heavy versions of high hp family of engines for pleasure craft.

"I'm intrigued about this Brunton's Autoprop H62 since it will mount to a standard shaft.


Beware , many of this style prop is made for sail or motor sailors and might not have the required blade area for a pure power vessel..

Check in Skines , what area you need or with your NA. The blades look thin to me.

The 80% load at 90% of rated RPM was given to me by an engineer that kept HUGE! gen sets going for years at desert hospitals.
\
For best efficiency a fuel map or BMEP graph is still required!!!!

DEMAND one before you purchase the engine.

Maybe they will part with one.

makobuilders said:

I'm intrigued about this Brunton's Autoprop H62 since it will mount to a standard shaft. The Southeast Asian dealer is working up a quotation for me. An extra 10-15% fuel savings could work out well in the long run, especially on a 60 ton boat that barely gets 1 nmpg.

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I would be cautious. I have an Autoprop on my 40' sailboat and love it. It allows me to motorsail very efficiently. It changes the effective pitch to account for the variable power being provided by the sail, allowing the engine to change its effective power at a given rpm. (or at least that is how my simple brain envisions it). It has allowed me to get very good motorsailing performance while reducing prop drag when strictly under sail.

A power boat is going to be different. I suppose that wind and sea state would be providing variable resistance much like my sail is providing variable assistance. But you don't need to worry about drag while under sail and the prop won't be as efficient in reverse. Brunton does a good job of sizing their props for different applications, but you want to be sure that the prop isn't providing too much load.

The only discussion more heated than anchors on a sailing forum is the discussion of props. There are some sailors that hate Autoprops and some, like me, that love them.

makobuilders said:

Regarding manyboats' comment, I had discussions with the EPA legal team and since your boat would be a repower then you would not have to abide by latest tier, only us guys dumb enough to be building new boats. Give it another year or so, and Tier 4 will be here - can't imagine how sucky that will be.

Click to expand...

The last I had read, the EPA was NOT going to require Tier 4 in the engines used by most trawlers/small boats. I hope that has not changed. I most likely read this when the engine emissions discussion was ongoing last year.

Later,
Dan

My little 37hp is Tier2.

Something I've been hesitant to introduce is best working loads for turbo'd engines compared to NA's.
Say you have a Cummins 115hp NA engine and you put in a turbo'd 210hp engine. I think they are basically the same engine. If the best working load for the NA engine is 50 - 70% load what would it be for the 210hp? With a Lehman a minimum load of 50% means a min. of 3gph as the FL burns 6gph at full load.

What will the 210hp engine burn at full load? And not a number derived by using the hour meter and gallons put in the tank but actual fuel flow. Would the 210 burn double or more at full load and rpm? Then the load per the 50-70 rule would be WAY higher heat wise and mechanical forces factor than the 115 engine.

Seems to me the 50-70 rule (that of course isn't a rule) would'nt apply to the 210 engine. I would guess that after all the variables were factored in the turbo engine's rule (if there was one) would probably be much lower than as a percentage of power delivered compared to max than the NA engine.

Or is the turbo engines so capable that they can run at 50-70% of max power just like the NA engines? And perhaps an engine designed as a turbo and was/is not offered as an NA may need yet another catergory of minimums and maximums.

What do you turbo people think of my thinking. Bashing permitted.

Tom I only have 900hrs on my Mitsu.