engine survey results

[Gregory]

Hi Guys, Looking at purchasing a 61 nordlund with qsm 11  was able to get an engine survey and oil sample results  cold start no sighn of excessive smoker or oil/fuel slicks noted  1 engine with 11.13 fuel dilution the other engine with  6.82% surveyor said likely cause likely injector pump since no soot found in fuel.  Said there should be 0 fuel in oil.  conflict in data .  The surveyor fuel burn data in the low range seems really high ( in gear)  . I checked with him and all data came from the smart craft system.

 

fuel burn                rpm                   port    star        combined   posted combined from broker  670 burn graph Idle                       593/625            2.9     2.8                   5.7                       3                       double ?          1.1

1000                     883/1237          6.5       5                    11.5                       4                      double ?              3

1200                                                                                                                11                                                    4.5

1500                     1448/1562        11         10                   21                                                                             8.6

1600                                                                                                                24                                                10

2000                      2131/1960      27          20                37        yes 27/20                                                   21.1

full                         2266/2360      33          34                67                                                                             33.6  

 

How can the fuel burn at low rpm be so high.  He insists there is no error.  He looked up other boats and they were more in line with the graph .   He said some boats are are harder to push.  The low rpm is way off the listed fuel consumption for prop curve.

  There is a note of reseal leaking after cooler inlet pipe connection. looks like corrosion, last cooler service 2019 no flushing system.  What are the odds of un serviceable coolers?

I am  attching the data monitor /logger     

 

1 Causes of fuel  oil in pan?

2 Why such a high fuel burn at low rpm?

3 chances of us serviceable after cooler 

 

 

Topic

[Rob Schepis]

That’s a weird one, sounds like someone may have installed a “spare tire” at some point…

[Francis Valerio]

I agree….wow

Who knows, I could have been a replacement that was marked incorrectly or read incorrectly by whoever installed it??? 

 

As long as a proper pitched prop makes everything nicy nice then you are good to go.  Good luck and good job on the follow up

[Gregory]

Found It

Not what I expected but I was right.  Now I know why no vibration on a bad prop. 

port 36 pitch starboard 34 pitch.  

Wow

 

[Francis Valerio]

Gregory

You are correct about the prop.  If it can be seen with a “stick test” then you can bet your butt that prop is way out…

 

Reducing the pitch or diameter both will help in gaining your RPM.  An experienced and reputable prop guy will help determine which would be better for you.  Different hulls can react a little differently and you can get your wanted RPM and still maintain speed to some extent by a combination of pitch/diameter and possibly  “CUP”.

That is why the prop guy gets the big bucks and if he dials you in correctly you will make up the $ in fuel savings and less wear and tear on the engines (and I emphasize wear and tear)

 

[Steve Lewis]

The advice on this site has always centered around removing Pitch as opposed to Diameter.  So let’s stick with that.  Also as I understand a large prop spinning slower is more efficient than a small prop spinning faster.  I am leaning toward 2 inches of pitch removed.  The scan should show if things are in check prop to prop or if they are different. 

Those Nordlunds look like a very nice low and slow, or “wine and cheese speed” as Tony puts it, cruiser.  I am guessing that you will spend most of your time at hull speed or less with the occasional run up to cruise power to get things good and warm?  If that is the case then you are probably good with 2 inches removed so targeting 34dx36p.  Tony might have a different recommendation but you can use that as a conversation starter with your prop shop. 

 

[Gregory]

The deal is done

Steve ,

Thanks for the info.   Bought the boat.  Did the sea trial and took burn data.  The port is loaded more, burns more fuel across the rpm range.  Considerably more in the upper range compared to the starboard side.  5 gal per hour.   My  personal feeling are there is a bad prop on the boat. They had a mechanic check things out and determine all is fine.  During sea trial  I felt some vibration in the lazaret but could not determine the side. I also saw a note in the survey “the props are only out of balance a-little based on the straight stick test”. What does that mean?  I always run class 1 props.  My understanding is if you can see, or hand measure a difference the prop is WAY out of spec..  So with all things equal the only thing that loads an engine is the prop and “props move boats”  ; I’m betting on this being a bad prop.

 I’m currently having all oils changed, fuel filters changed, water impellers changed. Ill do full seawater side this spring  once I get to my home port. I am having the props removed and sending to a prop scan shop.  Hopefully the starboard prop is close to stamped because that engine is burring less and is burning 22.5    , at 1800 18.5 .   

If I am correct , I want to pick up 200 rpm.   trans twin disk 2.53 -1, props stamped 34×38 4 blades. Semi displacement hull. I Shure the prop shop will be a resource , but I like being and informed consumer.

With the deep reduction how much pitch can I drop?  How much rpm will I pick up per inch of pitch change?

What is better less pitch larger wheel or  smaller wheel ( remove diameter) and keep pitch the same?

Greg

[Steve Lewis]

Greg,

A single oil sample is not of great value.  It is a snapshot in time with no context.  How long has this boat been sitting around?  Has current owner been excessively idling the engines at the dock?  Oil samples are of value when you sample on a consistent basis and watch the trend.

As for the fuel burn, were you on board for the sea trial that generated these numbers?  Tony has mentioned that fuel system restriction can generate fuel burn numbers that are incorrect.  Without knowing trans ratios and prop dimensions to see how things are setup, we are really shooting in the dark.

The only way you are going to get definitive answers on the coolers is by opening them up, having them serviced and then reassembled properly. You could always put a condition in the offer that the coolers be serviced before closing and if they are fine, the buyer covers that cost.  If the coolers are not fine then the seller covers the cost……  Something like that. 

As for the oil, you could always ask for the oil to be changed, take a sample of the fresh oil in the engine, then go back out on an extended sea trial(1-2hours) and get these engines and transmission up to full operating temps and then collect your fuel burn numbers.  sample the oil after the extended Sea Trial and compare that analysis to the fresh one.  Offer to cover some or all of those costs if you REALLY are serious about this boat.  While on the sea trial you can check the fuel system vacuum by looking at the vacuum gauges(if there are any on these Racors) and see if something is up there. 

Too much variability and unknown to give you a level of certainty at this point.  If you like the boat and you can get a good deal then you just need to ask yourself if you can tolerate these unknowns and the resulting cost of remediation of anything that is found after purchase.

I had to figure that out for myself in April 2021.  We ended up buying our current boat knowing full well that we had work to do.  480CE’s and old electronics.  I also had the entire cooling circuit serviced after purchase so that we knew for certain.  So we offered accordingly and the seller accepted the offer.

You can always try.  If the answer is not satisfactory, you can move on……

1 user thanked author for this post.

Tony Athens

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