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Old 03-07-2014, 00:34   #16
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Re: 4JH3 TE Cruising RPM 3000?

@ Dockhead

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Avoid like the plague any synthetics...
Why? I drive a turbo diesel VW and the factory insists on synthetics.

Just curious.

Doug
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Old 07-07-2014, 07:49   #17
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Re: 4JH3 TE Cruising RPM 3000?

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You may find this interesting - or not...

https://www.forkedrivermarinas.com/y...E_TechData.pdf

If I were propping this engine I would target hull speed at around 2800-3000 RPM and a max prop speed around 3500. This puts cruise in a fuel friendly (and quieter) operating zone for motoring and after 3500 the torque and power curves drop off. The zone between 3000-3500 keeps you on the torque curve and allows for some fouling of the hull and prop. i.e when fouled you have some "reserve" power.
Well I think I am way over propped !

Just had her out on the water yesterday and ran up the engine. No smoke but she sounded strained.

2700 RPM and a boat speed of 8 knots ! and this is not on flat water , it was blowing 18 knots on my port beam .

I didn't go higher then that as the engine sounded very strained , the Bristol is a lot of boat to move.

I have a Martec feathering 3 bladed prop.

Reverse has never been great with this prop and as I understand it , Martec's reverse well ?

Suggestions ?

Regards
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Old 07-07-2014, 08:10   #18
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Re: 4JH3 TE Cruising RPM 3000?

Well you were pretty much at hull speed at 2700 RPM - I'd say you are pretty close to being where you want to be.
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Old 07-07-2014, 09:44   #19
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Re: 4JH3 TE Cruising RPM 3000?

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Well you were pretty much at hull speed at 2700 RPM - I'd say you are pretty close to being where you want to be.

Thanks , I didn't really want to try to get full rpm (3800) out of her as she was almost going hull speed (8.2) at 2700, I'm sure it would have gone that fast in flat water . I want to be sure to work the engine from time to time as I understand diesels love to work.

I also checked my paperwork and the prop is a Max Prop , not a Martec . Not so easy to pitch the Max Prop.

Regards John .
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Old 07-07-2014, 10:03   #20
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Re: 4JH3 TE Cruising RPM 3000?

Re pitching a Max is easy but you do need to be hauled out. PYI will give you an optimum angle if you send them your boat and propeller details.

If you feel that your prop is over pitched then just reduce the angle by one degree and see how it goes.
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Old 07-07-2014, 10:05   #21
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Re: 4JH3 TE Cruising RPM 3000?

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Thanks , I didn't really want to try to get full rpm (3800) out of her as she was almost going hull speed (8.2) at 2700, I'm sure it would have gone that fast in flat water . I want to be sure to work the engine from time to time as I understand diesels love to work.

I also checked my paperwork and the prop is a Max Prop , not a Martec . Not so easy to pitch the Max Prop.

Regards John .
I'm not as familiar with the 4JH3 as I am with the 4JH4 but typically the 3800 RPM number is max rpm NO LOAD. The 4JH4 series specs 3200 RPM as max loaded and 3105 RPM as max continuous.

Your actual speed can vary large amounts depending on environmental conditions (sea state, accuracy of speed log, tidal or other currents, windage, etc.) so when setting up my boat, I go by the loaded RPM figures and try to get close but not over 3200 RPM at WOT.

When cruising, diesels like to be loaded so a cruise RPM of ~75-80% max continuous is a nice number which works out to be around 2400 RPM.

If going long distances and trying to conserve fuel, 1500 - 1800 works but then you should run the RPMs up every few hours to clear out the engine.

There is a theory on turbo'd engines that you want to keep the engine in a range where the turbo is kicking in but I don't have the science to back that up.

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Old 07-07-2014, 10:08   #22
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Re: 4JH3 TE Cruising RPM 3000?

Both my Yanmars were rated at 3600+ rpm. Both failed before 2500 hours. (pistons)After replacement and adjusting the max props both were run at ~2400 rpm... and no longer sounded like airplanes either! The only thing I can figure is: a) Yanmar is assuming you need all the HP their very liberal HP ratings show and need to run at high rpm to get it, B) they don't want the exhaust to soot up, but don't realize they need better designed pistons to run at high rpms.
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Old 07-07-2014, 10:45   #23
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Re: 4JH3 TE Cruising RPM 3000?

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Both my Yanmars were rated at 3600+ rpm. Both failed before 2500 hours. (pistons)After replacement and adjusting the max props both were run at ~2400 rpm... and no longer sounded like airplanes either! The only thing I can figure is: a) Yanmar is assuming you need all the HP their very liberal HP ratings show and need to run at high rpm to get it, B) they don't want the exhaust to soot up, but don't realize they need better designed pistons to run at high rpms.
So you run your engines at 2400 RPM's , how many hours have you got on them now.

Regards
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Old 07-07-2014, 10:55   #24
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Re: 4JH3 TE Cruising RPM 3000?

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So you run your engines at 2400 RPM's , how many hours have you got on them now.

Regards
Boat sold years ago.
I don't think Yanmar sells commercially rate engines in the US. But most Commercially rated engines are rated at different RPM based on use.
ie: the same engine may be rated at 2400 rpm for commercial use, 2800 rpm for intermittent and 3200 for pleasure use.
That should tell you something.... I guess it makes sense just rom a wear consideration... The bearings, pistons, rings etc in the engine will wear faster going 10,000 miles at 3600 rpm than at 2400 rpm if the same hull speed is attained.
You could drive your car from point A to point B in second gear and 4000 rpm, but I suspect it wouldn't be good....
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Old 07-07-2014, 11:01   #25
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Re: 4JH3 TE Cruising RPM 3000?

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Boat sold years ago.
I don't think Yanmar sells commercially rate engines in the US. But most Commercially rated engines are rated at different RPM based on use.
ie: the same engine may be rated at 2400 rpm for commercial use, 2800 rpm for intermittent and 3200 for pleasure use.
That should tell you something.... I guess it makes sense just rom a wear consideration... The bearings, pistons, rings etc in the engine will wear faster going 10,000 miles at 3600 rpm than at 2400 rpm if the same hull speed is attained.
You could drive your car from point A to point B in second gear and 4000 rpm, but I suspect it wouldn't be good....

I am mostly concerned about carbon build up and clogging up the turbo at lower operating rpm's . But I really don't want to over rev the engine either , just looking for a happy medium . I like to motor along at 2000 rpm , I will just have to wind her up every few hours just to clear the guck out .

Regards
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Old 08-07-2014, 01:27   #26
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I am mostly concerned about carbon build up and clogging up the turbo at lower operating rpm's . But I really don't want to over rev the engine either , just looking for a happy medium . I like to motor along at 2000 rpm , I will just have to wind her up every few hours just to clear the guck out .

Regards
I don't think there's anything in the world wrong with 2000, or even 1800, as long as you have a load on. Prop needs the right pitch. Going on 2000 hours, and I've never needed to clean my exhaust elbow, and turbo is always clean.
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Old 08-07-2014, 02:45   #27
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Re: 4JH3 TE Cruising RPM 3000?

Our engine which is the same as Dockhead and Dhillen, is happiest when we cruise at 2200-2400rpms using a Maxprop which was calibrated 18 months ago for a cruising speed of 7-7.5 knots at those rpms. Fuel consumption is around 1.5 gallons or 6 liters per hour for a 25 ton boat. If we cruise at 1800-2000 which produces 6-6.5 knots and uses 1 gallon or 4 liters of fuel per hour, I do rev the engine once per hour for 3-5 minutes. 3200rpms produces 8.5-9 knots, but I don't care to know what the fuel consumption will be at those revs. Early last season, we tended to cruise at 2400-2800 rpms, and noticed that fuel consumption was higher at 2-2.5 gallons per hour.

it's also important to make sure the prop is free of any hard growth, because that will cause a loss of revs.

Ken
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Old 08-07-2014, 15:25   #28
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Re: 4JH3 TE Cruising RPM 3000?

Couple of important notes:'

Fantastik: I said it SMELLS like it - not sure it is. I use the real Yanmar Turbo Wash.

Do NOT spin your turbo with compressed air. They turn at 60-80,000 rpms, but REQUIRE lubrication, which is provided by your running engine.

Your turbo should spin easily in place. You do have to remove the "silencer" to get to it. Don't use any metal tools on it - a small nick can put it out of balance.
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Old 11-08-2014, 11:01   #29
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Re: 4JH3 TE Cruising RPM 3000?

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Our engine which is the same as Dockhead and Dhillen, is happiest when we cruise at 2200-2400rpms using a Maxprop which was calibrated 18 months ago for a cruising speed of 7-7.5 knots at those rpms. Fuel consumption is around 1.5 gallons or 6 liters per hour for a 25 ton boat. If we cruise at 1800-2000 which produces 6-6.5 knots and uses 1 gallon or 4 liters of fuel per hour, I do rev the engine once per hour for 3-5 minutes. 3200rpms produces 8.5-9 knots, but I don't care to know what the fuel consumption will be at those revs. Early last season, we tended to cruise at 2400-2800 rpms, and noticed that fuel consumption was higher at 2-2.5 gallons per hour.

it's also important to make sure the prop is free of any hard growth, because that will cause a loss of revs.

Ken
Hi Ken,

I also was revving the engine for 3-5 minutes. Still the engine developed sot over time. I contacted Yanmar and they explained it has to be minimum 15 minutes in order to increase temp, in the combustion chamber.
3-5 minutes is not enough to increase temp.
It is not possible to blow out the carbon. Temp. has to be high to burn it.
The recommendation I got was 15-20 minutes every 4 hour. First time I did an Italian tuning with 30 minutes on full throttle. The sot problem has gone away after I started with the 15 min/4 hour.
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