Yanmar 4-JHE RPM's

[Highland Fling]

I run my naturally aspirated 4JH3E at anything between 1800 and 2500rpm almost never run it at max revs as all we do is dig a big hole in the sea.

Weather dependent this gives me 6/6.5 kts. with my four bladed FetherStream SS prop 7+ if we are not towing our RIB.

We have as of today 8,032 hours with my only significant problem apart from regular maintenance being replacement of the sea water impellor (buy the proper Yanmar ones with the threaded insert and the romoval tool is very very good and cheap) (I am going to change to the new 'Sppedseal life' one with the rotaing end plate that seemingly can run dry for up to 10 minutes at a time) and fishing the bits out of the oil cooler.

We have replaced all the rubber hoses once in 15 years and we have replaced the starter. It had a lazy pre engagement operation which meant regular removal and cleaning and we have replaced the alternator (Examining the old one {now our spare} the bridge rectifier diode block had some loose connections {two nuts} that stopped the alternator outputing smooth regulated DC) with a 90A one.

As this is an ex moorings boat we have a nice 'cheap to replace' Delco Remey alternator with a special foot bracket. I am thinking of upgrading that to a 110A version BUT with the solar we have and our LIFePO4 batteries and the removal of the engine driven refrigeration compressor (I am thinking of putting a CAT pump in its place for DIY watermaker) we almost never run the engine now on a daily basis.

I still have my original mixing elbow and the engine runs as sweetly as it ever did and with no worries or issues....

I love this engine and sadly the new ones are 'electronic' now and I don't get the mindset that thinks putting a turbo on a small sailboat engine is a good idea.

Double the horse power (turbo+intercoller) for a slight increase in weight and size yes.

But the downside adding a hot component in the same size small engine room that needs cooling AND papmpering (ensure you let it idle for 5/10 mins before shut down) (and make sure that you run it at max revs regulalrly to 'help' to decoke the turbo blades) never mind it needs more fresh cool air to breathe even with an intercooler seems like a not very clever idea doubly so in the Caribbean.

[Phoenician]

Going back over the logbook entries for when this data was collected, I find that the sog varied by up to +/- 0.5 knots along the course of the passages, most likely due to windage, current, etc, even when the sea was flat. A ballpark estimate would be as follows:

1900: 6.1 kn
2000: 6.4
2200: 6.9
2500: 7.5

The propeller is now an H6 Autoprop.

[Dockhead]

Originally Posted by Phoenician

Going back over the logbook entries for when this data was collected, I find that the sog varied by up to +/- 0.5 knots along the course of the passages, most likely due to windage, current, etc, even when the sea was flat. A ballpark estimate would be as follows:

1900: 6.1 kn
2000: 6.4
2200: 6.9
2500: 7.5

The propeller is now an H6 Autoprop.

Thanks, very interesting. You have the same engine and prop but you're a.ton or so lighter. Your consumption looks about the same as ours but your speeds lower - could be the way your prop is cut.

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[malbert73]

Have a 4jhe on my T40 with a 16 inch flexofold. Mine has a 2.17:1 tranny ratio in forward. I like to run it around 2200-2300 for fast cruising at 7 knots, 2000 rpm I agree is really nice relaxed speed which gives us 6.5 knots.
I just couldnt see running it at 85%. Too loud at 3000 rpm with 3600 rpm redline- it would drive me crazy.

After reading articles from Nigel Calder, and actually speaking with him at boat show 2 years ago, i felt comfortable overpropping just a little (added1 inch pitch) to load more at lower cruising RPMs. We just know not to try to get full rpms out of it. We never see a need to run above 2500 rpm. Engine has 2400 hours and going strong. To me, it's just like having an autoprop or adjustable feathering prop- I just have engine optimized for lower RPM cruising and recognize I can't run it continuously at 3300 RPM. My boat sails so well I'm mainly likely to motor in light/no air than in heavy stuff.


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[Ericson38]

We have a 4JH2-HTE (turbo) on our Taswell 49 (39,000 lbs in the slings), and a three blade feathering max prop. Prop rebuilt last year. I can get the engine to 3200 rpm which will sink the stern low enough to put the swim platform under water (8.4 kts), and get some black smoke, but not a lot of smoke...

Other data points look very similar to a previous post (54 ft Jeanneau), with light winds and <2 foot seas:

1900: 6.1 kn
2000: 6.4
2200: 6.9
2500: 7.5

I was under the impression that I needed to index the blades one notch less pitch, to raise the RPM about 300 for each of the speeds listed, but now wondering if I should do that.

[shawnkaplan]

I’m one of those guys who runs at 2,000-2,200. I never used to even try to run at full rpm, but after reading posts like this I feel I should be. pretty sure I used to get over 3,000 - likely higher. But now I’m only getting 2,750 at max. And the boat just feels sluggish. Bottom as prop needs to be cleaned for sure, but anything else I should check mechanically? Can I run it up to max without load for a few seconds? Like to check what I get without load.

Originally Posted by Dockhead

That's a typo -- the linked site says 2900RPM.

But 85% of my 4JH3HTE's max continuous would be 3230.

While the 4JH engines are smooth as silk compared to many other marine diesel engines of this size (I was amazed when I found out that they have no balance shafts), they don't sound nearly as happy at those speeds, as they do around 2000 to 2300 RPM, which for my engine is 52% to 60% of max continuous (which is 3800).

I would not get hung up on that 85%. An engine that sounds happy, IS happy. Just run it up to near redline under load from time to time, as Yanmar instructs.

[Wotname]

Originally Posted by shawnkaplan

I’m one of those guys who runs at 2,000-2,200. I never used to even try to run at full rpm, but after reading posts like this I feel I should be. pretty sure I used to get over 3,000 - likely higher. But now I’m only getting 2,750 at max. And the boat just feels sluggish. Bottom as prop needs to be cleaned for sure, but anything else I should check mechanically? Can I run it up to max without load for a few seconds? Like to check what I get without load.

I wouldn't worry about anything else until the prop and bottom is cleaned. You could be surprised about how much difference a dirty prop and bottom makes.

Yes, it doesn't hurt to run up to max rpm in neutral for short periods.

Great to see your first post after all these years .

[hpeer]

Originally Posted by shawnkaplan

I’m one of those guys who runs at 2,000-2,200. I never used to even try to run at full rpm, but after reading posts like this I feel I should be. pretty sure I used to get over 3,000 - likely higher. But now I’m only getting 2,750 at max. And the boat just feels sluggish. Bottom as prop needs to be cleaned for sure, but anything else I should check mechanically? Can I run it up to max without load for a few seconds? Like to check what I get without load.

The FIRST question is is can you get higher RPM in neutral?

I had a problem with my fuel pump (Governor gunked up) that limited me to 16,500 fed/rev/neutral. If it revs up in neutral then it’s related to load; prop, bottom, elbow carbonized, etc. If not then it’s surely something with the engine.

Not a conclusive test, if it does NOT rev up in neutral you know something important. If it does not you have not eliminated much. But super easy to do.

I have frequently run as low as 1,600 to 1,800 for extended periods while occasionally running it up to 3,200. The fuel usage is much better at those lower RPM. Look at the fuel consumption curve.

[zmike]

Informative post... I have a new to me 4JHE engine. I have limited hours on it, but it naturally seems to move along around 2100 RPM's. More than that and it seems to get louder, but not much more speed. 2100 seems to be this nice good speed for the boat, which tends to match up with others in the thread.