55 years ago my wife and I built a 28' sailboat to go cruising.  I put in a single cylinder, 5 HP Yanmar that I purchased cheap in Mexico.  It had a hand crank start, no starter motor, but with a huge propellor it pushed us at hull speed (4.9 knots).  I added an alternator but it would not push the alternator and boat at the same time.  The best part though was that it got 10 hours per gallon of diesel. The fuel tank was 40 gallons and we ran it for 9 days straight continuously between Rarotonga and Tonga making 100 miles per day and we still had fuel when we got there.  It never failed to start.  I loved that little engine.

Have had a 3gm30f freshwater cooled in 1990 Hunter 30.  It now has 1550 hours on it.  Everything in the video has occurred, follow advice given, and you'll be fine.  Just wish I had this video 25 years ago!  Biggest and most frequent problem has been the mixing elbow, which I was cleaning out or changing at least every 300 hours.  Went to a stainless model five years ago.  Pulled it after 300 hours this year and was astounded to find it perfectly clean, looking like brand new.  Highly recommend this aftermarket change.
  This era of engine also had starting issues that were solved with a better starting solenoid.  Replaced 20 years ago and have forgotten about it.
 Don't baby these engines!  Test run at wide open throttle and back down till no smoke!  Most say cruise at 80% of WOT; (3600 * .8 = 2880) but I started running around 3k a few years ago for cleaner exhaust and a little better mileage.  Still leaves a little soot on the transom (mostly because of the exhaust hole placement no the starboard side at waterline, instead of directly aft), but never visible.

After 30 yrs of sailing CA and MX coasts, and three round trips to HI, I'm very happy with the 1986 3HM35F that re-engined our 1974 36 ft sailboat (I36).  This video is spot on. The stock exhaust elbow needs to be replaced every 5 to 7 years. About 10 yrs ago I replaced it with a SS one and it looks good (recently dissassembled to inspect). I've replaced the engine mounts three times. Some parts for this 40 yr old engine are getting hard to find.  The ganged decompression lever is a good thing to have for emergency shut down (don't overfill the crank case!)  Maintenance per the Yanmar manual is very easy. The only repair I've hired a pro for was to replace the Kansaki shaft and shifter seals.  A bit over a year ago I replaced the stock 35A Hitachi alternator with a Balmar kit (125A, serpentine belt...) so far (over 100 hrs) it's working well!

Best sail creator on YouTube ATM. Thanks for your hard work Brother. Hope to see you on the water soon.

Great video, Tim, keep them coming!
A commonly neglected maintenance issue that was not mentioned is replacing the motor mounts. I believe Yanmar's recommendation is to do it every five years.
Worn-out mounts will get the shaft misaligned, a leaking packing gland, particularly when heeling, and even engine problems because of the bouncing around.

I have just purchased a yacht with a Yanmar3GM diesel engine. She needs a complete service and overhaul. The great thing about these engines is spares are easy to find and they can be worked on in the boat. I will definitely be replacing the exhaust elbow and sail drive shaft.

40 y.o 3GM-F with 3,200 hours. Lake Ontario, seasonal use.

Got bright nail polish & marked all the bleed screws on the fuel system. Got good at it while diagnosing an air leak in the fuel tank.

I love the simplicity. It just starts & runs.

for a repower I'd look at Beta (based on Kubota engines) and Nanni as well as Yanmar.

I’m so amazed at how advanced sailboats have become with electric and hydraulic winches and all the other fancy gadgetry. I noticed that almost all new sailboats come with Yanmar engines now. Still, I miss the 1970 30-ft Islander I grew up with (I was the “engineer”, hand-cranking our 2-cyl Volvo diesel engine). I swear, short of running out of diesel, I don’t think you could’ve hurt that engine if you shot it.😊

The reputation of Yanmar is big in the sailing world. I believe there is a reason for this so I would not shy away from a boat with a Yanmar. However, I’ve been running a Volvo and I have had very good luck with them.

Yanmar started as an engine company.  If you visit Japan you will be surprised to see that it is well known in the domestic market as an agricultural equipment maker.  Most Japanese are unaware that overseas the boat engine product line is well known.

My 25 year old Yanmar 3GM  works great

Sorta missing the old Practical Sailor spreadsheet showing reliability or effectiveness of comparable products after some Consumer Reports styled home brewed testing  procedure. This sounded more like a paid yanmar ad. The merits of Yanmar vs Volvo vs Beta is a discussion worth a few beers.

Hi Tim! have the Yanmar 3GM and it’s 30 years old with about 1600 hours. The one weakness I found with this Yanmar is the external oil line. It is known to corrode & leak which recently happened to me. It’s a job to replace it. And as Tim pointed out, the impeller will go as well so replace it every year or few years. Keep up the great videos!

I frickin love my Yanmar 4JH in our J/133. I know that if I take good care of it, it just keeps on tickin’. So good.

Really useful content here both in the video and in the comments below. I've owned a 2001 Yanmar tractor for about five years, it has over 2000 hours on it but despite burning a bit of oil, it still runs great and never lets me down. I'm in the process of buying an Achilles 840 28 foot sailing yacht powered by a Yanmar 2YM15. I'm pretty sure that the exhaust elbow needs to be replaced and I plan to replace all filters (and keep spares on board) so the information in this video is both timely and topical for me. Thanks 🙏for (yet another) interesting and informative video - keep up the good work! 😁

Do the pentas next!!! Please!

I love the content here at Practical Sailor and Lady K sailing. My wife and I are just beginning our sailing journey, and your videos are helpful.

Yanmar? Excellent. What I don't like is seawater cooling in any form, nor watered exhaust. I've seen that diesels like to run at a very low 10-20% horsepower, but hate the lowest idles. You don't see anything like my 22 to one compression in boat diesels. They don't climb mountains to 12,000 feet, nor operate in deep cold. What I like about my air cooled Situan Sifa are these facts: Undersized means excellent for turning an alternator. Hand pull start. To change the oil, run it hot, disconnect, pick it out, and pour all the oil out the fill port. I've never used the empty plug. Steel gears and no timing belt. Utterly mechanical injection. I've never air bled the fuel system. Just hit the decompression lever and cranked out the air. The aluminum and steel castings are excellent without defects. I made my dry exhaust adaptation out of stainless steel.

I have rebuild many gas engines, 4,6,V8s, and two Yanmar 3GMF from scratch, bare block, bare head, etc. My own 3GMF #1 cyl seized while on the hard unattended. When I first saw those cylinder wall, I was stunned. They had so much wall thickness, I was blown away. I was hoping to "upgrade" to a 3GM30F, (the other engine I rebuilt), but couldn't convince the owner to a deal. Indeed they are bulletproof, and better if maintenance is done regularly.
You forgot that Yanmar also has a big market for farm equipment, especially John Deere.
As for the salt water intake for cooling, I devised a way to put a fresh water hose when at a marina and flush the engine at the same time as oil changes, if I'm then at a marina. I've never been a fan of saildirves. I rather deal with the stuffing box and the cutless bearing. Great video Tim.

I like my Yanmar 4JH4 with saildrives. However, in my experience the main cons for Yanmar Sail Drives are the SD50 slipping clutch problems and damage to the leg/prop seals often caused by fishing line. Ingested fishing line cuts the seals and let sea water in and oil out. It's amazing that a sail drive with completely contaminated oil will keep operating so well. But it will eventually ruin the bearings and cogs. The SD50s can also have a spacer alignment issue with the drive cogs. This can badly damage the teeth. The new SD60 sail drive has a ZF gearbox which seems to be smoother and no clutch problems. The new SD60 uses engine oil not leg oil.