Engine cost per hr of operation

[CarlF]

My understanding is that the Yanmar recommendation for several quick full RPM revs (in neutral) before shutdown isn't about heat. It is to blow any carbon or oil deposits through the exhaust manifold and turbo. These tend to build up even in a hot engine while doing a typical slow speed run into the dock. After the bursts, don't shut down immediately. Give the turbo a minute to spin down.

It's equally important to give your engine an occasional hard run - I do 5 minutes at full throttle during an hour at 2500 RPM once a week (for a 3100 max RPM Yanmar). Obviously do this only on a fully warmed up engine.

[TacomaSailor]

WAY MORE than you want to know!

For my Yanmar 4JH2E with 2500 hours on it in the last 20-years the HOURLY costs are:

$3.75 Direct Operating
$1.40 Major parts replacement
$0.31 Minor parts replacement

$5.46 PER HOUR to run the engine

And I would add in the cost of $0.59 per hour to turn the prop shaft connected to the Maxprop.

That works out to be $6.05 per hour or about $1.00 per Nautical Mile.

DETAILS:
Fuel 0.8 GPH at 6.4 knots
Oil Replace 5 quarts every 150 hours
Oil Filter Replace every 300 hours
Fuel Filter (Yanmar) Replace every 300 hours
Fuel Filter (Racor) Replace every 150 hours
Coolant 3 quarts Replace every 300 hours
Raw water impellor Replace every 300 hours
The costs above (at current fuel and oil costs) come to $3.75 per hour

Heat Exchanger $1,300 replaced at 2400 hours
Mixing Elbow $550 replaced every 1000 hours
Fresh Water Pump $265 replaced at 2000 hours
Starter & Solenoid $310 (OEM) replaced at 2400 hours
Motor mount $165 replaced at 2400 hours

Other Parts $500 spread over 2400 hours

I had to replace the cutlass bearing ($35) and prop shaft ($650) at 2400 hours
I repack the packing gland at $15 every 300 hours

I’ve had the Maxprop rebuilt twice at a total cost of $600 spread over 2400 hours


There are NO labor costs included in any of these numbers. I do all my own maintenance. Labor would have added 20% to 50% to these costs.

[GILow]

Truly excellent data. Thank you!


Sent from my iPad using Cruisers Sailing Forum

[GordMay]

Originally Posted by GILow

... I figured 5000 hours for a boat diesel, is your 10,000 hours above for a boat diesel or an aircraft engine? In other words, do you think I am being pessimistic assuming 5000 hours? ...

I believe 10,000 Hrs to be a reasonable life expectancy (to re-build, not to scrap) for a naturally aspirated marine diesel engine.

Originally Posted by CarlF

My understanding is that the Yanmar recommendation for several quick full RPM revs (in neutral) before shutdown isn't about heat. It is to blow any carbon or oil deposits through the exhaust manifold and turbo. ...

And, to not leave unburned fuel on the cylinder heads.

[GILow]

Originally Posted by GordMay

I believe 10,000 Hrs to be a reasonable life expectancy (to re-build, not to scrap) for a marine diesel engine.
.

Well that's jolly good news. That means it will out-last me.

[EveningTide]

TacomaSailor- Thanks for the excellent data (I've copied it for future reference). You didn't mention injectors- have you needed any maintenance there? I am at 2600 hrs in 12 years on a Yanmar 2GM20F and have not done anything beyond normal maintenance (my intervals are similar to yours although I change oil more often). I worry some about the mixing elbow since this seems to be a common problem but I do try to run it hot at regular intervals as recommended in the manual.

[TacomaSailor]

"You didn't mention injectors- have you needed any maintenance there?"

I had the injectors replaced at 75 hours on a warranty issue. The local Yanmar dealer thought the factory put in the wrong ones.

I recently talked to the local Yanmar shop in San Diego about the injectors because they now have 2400 hours on them and are 20-years old. I thought maybe they should be tested for spray pattern.

The shop asked me:

- is there black smoke under load
- does the engine start quickly and easily
- will the engine reach 3600 RPM in Neutral

My answers were NO, YES, 4000

The Yanmar shop guy said - "Your injectors are fine" He continued by saying they never test them ($100 per) unless there is some symptom of poor spray or opening/closing problem. He said the injectors fail gradually and will not cause any serious problem, other than poor running, as they fail.

"I worry some about the mixing elbow since this seems to be a common problem but I do try to run it hot at regular intervals as recommended in the manual."

That was exactly my attitude until water started spewing from the joint between the heat exchanger flange and the mixing elbow. The mixing elbow had eroded away inside and allowed salt water (raw water injected into the exhaust stream) to splash back on the heat exchanger flange. That salt water corroded away the flange.

I am sure that IF I had inspected and replaced the mixing elbow at a shorter frequency I would not have had to replace the mixing elbow at a cost of $1,300.

Removing and inspecting the mixing elbow on our boat is easy and I should have been doing it at least every other year.

[a64pilot]

Originally Posted by valhalla360

a64pilot: It may be figured all the time but does it have any relationship to reality? Then again aircraft have strict govt regulations to follow that boats do not.

Yes, it's generally very accurate, excepting accidents of course.
Actually a Part 91 aircraft has really very little government regulations as to engine maintenance and operations and many if not most engines are flown well beyond TBO

[a64pilot]

Originally Posted by GILow

I have always been fascinated by this aspect of aircraft maintenance, and as my son becomes more and more involved in flying these numbers are starting to prey on my mind a bit.

I figured 5000 hours for a boat diesel, is your 10,000 hours above for a boat diesel or an aircraft engine? In other words, do you think I am being pessimistic assuming 5000 hours?


Matt

TBO for an aircraft engine is usually around 2,000 hours. Many are run "on condition" and go way beyond that, some do not make TBO, a lot has to do with how it's treated and maintained.

I believe if a boats Diesel is well maintained and operated, it should go 10,000 hours before overhaul, but I believe you can kill one in a few hundred too if you try hard enough.

[EveningTide]

Tacoma- Thanks. I still have a slight bit of confusion. You say-

"had eroded away inside and allowed salt water (raw water injected into the exhaust stream) to splash back on the heat exchanger flange"

Would frequent inspection have somehow stopped this erosion or just let you know it was happening? Seems you would have had to change the elbow anyway. Did waiting until you saw the external leak somehow cost you extra?

Do you have any thoughts on removing the elbow and cleaning it to remove the carbon? Would this extend its life?

Also your experience with injectors is like mine. Mine is still starting and running fine so I have left them alone. No smoke, no difference in fuel consumption, etc.

[hellosailor]

With proper care, a marine diesel (the big od slow ones, or the faster lighter new turbos) supposedly can go at least 20,000 hours with a "major" overhaul every 5000. Your numbers will vary but you should be able to find a set you can accept, then add the cost of all those overhauls (which could mean down time for the boat) done by a professional until the end-of-service at 20,000, or whenever.

And as all the MBAs will tell you, if the engine cost $20,000 to buy, ship, and install/replace? That's another $2000 or so you've lost every year, by tying that money up in the engine instead of someplace else with a return on your money. $2000, maybe 200 hours in the average years? Could be an extra $10 per hour hiding there. And a little more perhaps, to insure and register a vessel with a fuel system and engine on it?

[TacomaSailor]

"Would frequent inspection have somehow stopped this erosion or just let you know it was happening? Seems you would have had to change the elbow anyway. Did waiting until you saw the external leak somehow cost you extra?"

I like to think more frequent inspections would have saved the heat exchanger. Otherwise Yanmar has a terrible design with incompatible metals and corrosion.

Have you seen the long discussions I started here about Yanmar mixing elbows and heat exchangers:

http://www.cruisersforum.com/forums/...ed-135915.html

http://www.cruisersforum.com/forums/...es-135802.html

and here?

Can this Yanmar Heat Exchanger & Elbow be saved? - Trawler Forum

[darylat8750]

"The Yanmar shop guy said - "Your injectors are fine" He continued by saying they never test them ($100 per) unless there is some symptom of poor spray or opening/closing problem. He said the injectors fail gradually and will not cause any serious problem, other than poor running, as they fail."

$100 per to test? If they remove and replace maybe it would be worth that. I removed 12 injectors from my two Ford Lehmans and took them into a fuel injection shop that rebuilds for trucks in an industrial type area. Test, clean, replace all the little o-rings and copper crush washers. $12.50 each for 8 of them. Four of the twelve needed new injector tips and those were $47.00 each.

I think of the mixing elbows as a consumable item. Most engines have a recommended time (engine hours) between replacement. I would ask about years between replacement also.

[EveningTide]

TS- Thanks for the links- Much more than I wanted to know (who wants to know so much bad news). I vote for the one who said if everything is installed just right the salt water will not come back to the manifold. I also like the one about custom stainless steel mixing elbows. I saw one on a different motor and was very impressed. Couldn't see how it could give much trouble.

[ozskipper]

Originally Posted by T.Emigh

It seems to me in one of Nigel Calder books he had explained the actual cost per hr of running your engine. I know it varies with size, but I have a 65 hp Perkins and I would like to know what it cost to run it on a per hr bases.
Does anyone have that information from his book or know what it works out to be?

Hmmm I read something similar in "occupation circumnavigater". If thats on your shelf, I am sure it has the info you are looking for.