Governor/WOT?

Scary,

I think what you have was done most likely by Hatteras. Indicated by the fact that two others you found were setup the same.
Also that your book says rated rpm is 2800 so, to me, there has been some customizing.

Your boat is a full displacement hull or nearly so built to be an economical seakindly boat at hull speed, not planing or semiplaning.

Hatteras used the DD because they were good strong engines capable of operating many thousands of hours with decent service and servicing.
However, Hatteras realized the engines were capable of producing much more power than the hull could use so there is a limiter somewhere to prevent engine abuse and wasting large amount of fuel.

Hatteras could have asked DD to modify the injection pump and reduced the rating but I think, can't say for sure, that if done by DD, DD would have left a RATED and a HIGH IDLE that were different. The fact that your APPARENT rated and high idles are the same tells me the throttle is limited somewhere by a stop.

You can check if you wish but since your hull likely cannot use any more power there is no point other than just to know. They apparently left you with somewhat more power than the minimum to move the boat at hull speed to account for head seas or winds. Good and I'd be surprised if that were not so.

With this setup Eric has a point that you could be overpropped and not know it. If the engine had been derated by DD and a new rated and high idle left then you could use those differences to determine propping suitability. With a stop the governor could feed more fuel than the engine can use at that max rpm if the load is too high. The best way to monitor is the use of a pyrometer and watch for high EGT in your case.

"Hatteras could have asked DD to modify the injection pump and reduced the rating but I think, can't say for sure, that if done by DD, DD would have left a RATED and a HIGH IDLE that were different. The fact that your APPARENT rated and high idles are the same tells me the throttle is limited somewhere by a stop".

2 stroke DD are set to the power required by the injectors.

They (the injectors) ARE the injection pump.

The proper technique to reduce engine power on a DD is to install an engine with fewer cylinders.

That way they all work at over 60% , so the efficiency is high.

Probably the add dept nixed the more rational/efficient engine choice .

FF

Interesting comment

FF said:

"Hatteras could have asked DD to modify the injection pump and reduced the rating but I think, can't say for sure, that if done by DD, DD would have left a RATED and a HIGH IDLE that were different. The fact that your APPARENT rated and high idles are the same tells me the throttle is limited somewhere by a stop".

2 stroke DD are set to the power required by the injectors.

They (the injectors) ARE the injection pump.

The proper technique to reduce engine power on a DD is to install an engine with fewer cylinders.

That way they all work at over 60% , so the efficiency is high.

Probably the add dept nixed the more rational/efficient engine choice .

QUOTE] The 58 lrc was available with the 4-72 and the 6-72 so there you have it. Most west coasters preferred the 7-72 over the 4-72 for the wave conditions on the west coast. I believe there are a few 48's with 120 hp Lehmen's so Hatteras must have felt 120hp was the right amount of power. I don't use anywhere near that cruising.

Click to expand...

Bottom and prop condition also affect whether a mill will reach theoretical WOT under load particularily when the vessel is geared and propped to be at or above hull speed at WOT, and does not have an abundance of horsepower, meaning enough to bring the boat on a semi plane.

Secondly most modern diesel manufacturers recommend 'racing' the engines as well as a limited amount of time at WOT under load as maintenance practices for the fuel injection system, the high engine rpm and load removing combustion residues from injectors as well as breaking carbon deposits from ring sets.

I can not speak for Lehman engines, but this is the case for Cat and Yanmar. In the vessel cited above, a 48 LRC Hat with dual 120 hp engines would not be able to push itself very far up the bow wave even at WOT, thus hull growth and prop condition would definitely affect hp demand and impede attainment of theoretical WOT under load.

"mill"???
You mean engine?
I have'nt heard that expression since I was a teenager.
Are yiu a teen ager?

What's "theoretical" WOT? WOT is WOT.

One dos'nt gear/prop to achieve a boat speed......you gear/prop to achieve a specified engine speed that insures a certain engine load. Whatever the boat goes the boat goes.

"racing" engines for recommended maintenance? Interesting approach. Sounds like it could have merit though.....if the engine was loaded correctly.

"Growth and prop condition" is usually considered maintenance.

Sounds like your'e from another planet. Florida.....oh I see.....you are from another planet. Being from Alaska (at the moment) it seems that way anyway.

Interesting comments Tim and I believe there are many here that speak for and against Lehmans.

manyboats said:

"mill"???
You mean engine?
I have'nt heard that expression since I was a teenager.
Are yiu a teen ager?

What's "theoretical" WOT? WOT is WOT.

One dos'nt gear/prop to achieve a boat speed......you gear/prop to achieve a specified engine speed that insures a certain engine load. Whatever the boat goes the boat goes.

"racing" engines for recommended maintenance? Interesting approach. Sounds like it could have merit though.....if the engine was loaded correctly.

"Growth and prop condition" is usually considered maintenance.

Sounds like your'e from another planet. Florida.....oh I see.....you are from another planet. Being from Alaska (at the moment) it seems that way anyway.

Interesting comments Tim and I believe there are many here that speak for and against Lehmans.

Click to expand...

Funny...I understood what he was saying....unfortunately there really isn't better standardized "terminology" with engines through the years. My Lehman manual calls it "gross power" xx hp at xxxx RPM....never heard it referred to that before that manual. So his use of WOT was what the manuf. says you get at the pins whereas others know WOT is what you get at the pin. Certainly we all agree that growth loads up the engine and may reduce the recommended max RPM...and a vessel engined near it useful power versus overpowered suffers speed while all will suffer fuel burn.

Many of the higher speed, modern diesel manufacturers recommend so many minutes of max throttle if you have been underloading them for long periods...some I have heard /read recommend it at the end of the day no matter what...just to make sure.

Mill???? hear it every once and awhile...but not like yesteryear...maybe more aviation oriented because I don't hear it as much since I've been away from aviation..

psneeld,
I remember "mill" as a slang term used by hot rod guys and wanna be's. In car magazines too but have no idea if it's used today.

It does sound like tinb7734 is into faster boats. That's fine......I'd rather go twice as fast as I go in Willy.

And yes .....lots of trawler guys never ever run their engines at full or near full power. They think ther'e engines are going to fly apart or somth'in. But if they are over propped it's just as well. But they need to find out. Under propped a little (50 - 100rpm) is fine too as far as I know but I think running at WOT for brief periods is most valuable as a test to learn that nothing performance wise has changed. But MOST importantly it needs to be done as a step to insure a boat's engine is correctly matched to it's load......the propeller and gear ratio. When I first bought Willy (w her original Perkins) the engine ran perfect until I opened her up and after about a minute the engine quit. We need to know if our "mills" are there for us to perform at 100% or more importantly to know if there is something wrong.

Just a little deuce coupe with a flat head mill
But she'll walk a Thunderbird like (she's) it's standin' still
She's ported and relieved and she's stroked and bored.
She'll do a hundred and forty with the top end floored
She's my little deuce coupe
You don't know what I got
(My little deuce coupe)
(You don't know what I got)

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I think this is the only time I can remember someone referring to "mill".

manyboats said:

psneeld,
I remember "mill" as a slang term used by hot rod guys and wanna be's. In car magazines too but have no idea if it's used today.

It does sound like tinb7734 is into faster boats. That's fine......I'd rather go twice as fast as I go in Willy.

And yes .....lots of trawler guys never ever run their engines at full or near full power. They think ther'e engines are going to fly apart or somth'in. But if they are over propped it's just as well. But they need to find out. Under propped a little (50 - 100rpm) is fine too as far as I know but I think running at WOT for brief periods is most valuable as a test to learn that nothing performance wise has changed. But MOST importantly it needs to be done as a step to insure a boat's engine is correctly matched to it's load......the propeller and gear ratio. When I first bought Willy (w her original Perkins) the engine ran perfect until I opened her up and after about a minute the engine quit. We need to know if our "mills" are there for us to perform at 100% or more importantly to know if there is something wrong.

Click to expand...

I think tinb7734 knows that and is saying you'll never get to WOT if you're all dirtied up..

Interestingly: The word "Mill" referring to auto engines was a slang term used (and I think the term may have actually originated) in the clandestine distilleries’ "Booze Running" days... reason was... “Gin Mill" to bootleggers was a common term. The drivers took up the word in reference to their engines because they found that the engines performed even stronger if they added some of what they called the “high test” (98 proof or better) distilled alcohol to their fuel. Thus, they started a slang term, calling their engine their “mill”

How do I know this: Starting in 1976, at 6K ft. elevation in Sierra Nevada Mountains, for 7 years I was in construction partnership with a tough old boy named Ivan (and I do mean tough!). He and I became primary masonry and concrete contractors on an 18 hole golf course, octagonal Club House protruding out the side of a mountain cliff, and the adjacent 750 condominium project. Ivan was in his 60’s I was in my 20’s. He was the money and biz smarts, I was the estimator and job site ramrod. I learned a lot from Ivan. We together hired workers and had up to 50 on payroll in the best of times. Ivan and I became great friends and worked very well together, made lots of money, and shared many a drink and raucous night! To the point - -> Ivan had been a hot-rod driving booze-runner, back in his very young days! He told me many a story. The reason for calling the engines the Mill was one of them. Ivan would only run illegal booze in Chryslers because he said they were the fastest cars then on the road. In the 70’s and early 80’s he still would only drive Chryslers. He told me that things were in his favor in a road race with the cops with a Chrysler but that all changed when the cops got radios in their cars and he got nabbed because of that. He quit driving booze after that.

Art, that is an interesting story. Thanks!

MILL

Long before the internal combustion engine there were many types of mills (engines) or better said devices to rotate things to perform work. Terms used include:

Horse mill - these poor guys went roundandround their entire lives to pump water or grind grain
Water mill - grain and textiles
Wind mill - pump water