Pilot 30 Cruising Speed- How fast are you going ?

[nveater]

So I have 1999 Pilot 30 with a Cummins 6BT 210 hp engine- this is my 3rd season with the vessel after 37 years with various sailboats. As a former sailboat guy I'm thrilled anytime I'm above 5 knots, but it has gotten me wondering at what other Pilot owners are running their boats at. At 2400 rpm (WOT is 2650), I am cruising in the 11- 12.3 kts range ( yes I have seen higher up to 15 kts, but not very often). I do like to throttle back and cruise in the 9-10 kts range. I realize that this Cummins, a very reliable engine, is probably the smallest hp engine for the pilots and that later iterations with the Yanmar had a bunch more HP. So I would love to know if other Pilot owners with this model engine are seeing similar speeds? More curious than concerned -

Thanks

 

[Mainship Pilot]

2004 Pilot II 30, 6LPA 315 Yanmar, I typically cruise at 2800 rpm's, with a tow, 11' 325# console style dingy behind. I keep it there around 14 knots, as the dingy likes that speed. If not towing, I gain about a knot, at 3000 RPM's, it's a 16 knot cruise, depending on wind and sea conditions.

 

[Mainship Pilot]

2004 Pilot II 30, 6LPA Yanmar, I typically cruise at 2800 rpm's, with a tow, 11' 325# console style dingy behind. I keep it there around 14 knots, as the dingy likes that speed. If not towing, I gain about a knot, at 3000 RPM's, it's a 16 knot cruise, depending on wind and sea conditions.

 

[nveater]

Thanks very interesting that extra 100 hp from Cummins to Yanmar, very nice

 

[DavidM]

Well, that same Cummins block can be had with 380 or even 425 hp.

The Yanmar 6LP at 315 hp is a perfect match for that boat.

But enjoy your Cummins 210 hp engine. You could run it at wot and it probably wouldn’t hurt it at all. That is according to Tony Athens, the Cummins guru on Sbmar.com.

210 hp should push it to similar speeds as the Yanmar at 2,800 rpm.

David

 

[Mainship Pilot]

Well, that same Cummins block can be had with 380 or even 425 hp.

The Yanmar 6LP at 315 hp is a perfect match for that boat.

But enjoy your Cummins 210 hp engine. You could run it at wot and it probably wouldn’t hurt it at all. That is according to Tony Athens, the Cummins guru on Sbmar.com.

210 hp should push it to similar speeds as the Yanmar at 2,800 rpm.

David

David, Assuming your last statement, the 6LPA burns about 7.5 - 8 GPH at 2800rpm in my Pilot 30. What would you guess the Cummins 210 would burn at that same RPM, assuming that's WOT or thereabouts?

 

[DavidM]

Well, your 6LP makes about 18 hp per gpm of diesel so it is producing about 8*18= 144 hp, much less than the Cummins at wot- 210.

If they were both making the same hp, the fuel burn would be about the same.

Remember, the Cummins makes its maximum hp at about 2,600 rpm, your 6LP makes it at 3,800 rpm.

David

 

[nveater]

So for fuel burn- I ran my Cummins pretty much in the 2400 range the first two years I had it and I was getting about 6.8 GPH- this year I have been running it for longer periods at lower rpm (2K or below) and have averaged 3.7 GPH- one of the drawbacks of the higher rpm is the noise. The engine bay is insulated but I was going to ask this forum about what they have down for sound proofing. At 2400 as I said I get between 11.5 and 12.3 kts- I have pushed it to 2600 and am getting 15+ kts there but am sort of nervous about running it at WOT for very long- this is (for me) an interesting discussion and I appreciate all the comments and insights- I am also wondering whether I am propped correctly- (I do have my prop information but its on the boat)

 

[Mainship Pilot]

Noise is probably the biggest drawback of the 6LPA, it’s LOUD at cruise! When we cross to Catalina, 26 miles, it’s pretty much in silence between the admiral and I. Otherwise we would just be yelling!

 

[Duetto]

fwiw, we have run our yanmar 4jh3's at 3400 (3800 wot) for 20 years/4000 hrs. this is not on our mainship but a commentary on how you can run a diesel.

 

[BB-marine]

So for fuel burn- I ran my Cummins pretty much in the 2400 range the first two years I had it and I was getting about 6.8 GPH- this year I have been running it for longer periods at lower rpm (2K or below) and have averaged 3.7 GPH- one of the drawbacks of the higher rpm is the noise. The engine bay is insulated but I was going to ask this forum about what they have down for sound proofing. At 2400 as I said I get between 11.5 and 12.3 kts- I have pushed it to 2600 and am getting 15+ kts there but am sort of nervous about running it at WOT for very long- this is (for me) an interesting discussion and I appreciate all the comments and insights- I am also wondering whether I am propped correctly- (I do have my prop information but its on the boat)

The max fuel burn for a 210hp 5.9 cummins is 11.2 GPH This would be 100% load. Using 210hp/11.2 gpg = 18.75 hp per gallon burn. 100% load= 11.2 GPH, 80% load = 8.96 GPH. This would be the goal I would shoot for 80% load would be an efficient and maintain the longevity of the 5.9 L cummins @210. 80% load would be using about 170 hp.

Based on your fuel burn 6.8 gph and 2400 rpm I believe you either have wrong fuel burn calculations or or you are under propped. Based on your max rpm posted on this forum 2650 rpm you would be correctly propped or slightly over propped. The rule of thumb is 100 to 150 rpm above rated HP RPM which is 220@ 2600 rpm.

My guess would be your fuel burn numbers are a bit off. Using 12Kts = 13.8mph as an average speed at 2400 rpm @ 6.8 GPH would give you fuel economy of 2.03 mpg. 2400 rpm @ 8.96 gph ( my calculation)= 1.54 mpg which I believe is a true realistic number for continuous run at 2400 rpm. I do believe that if you cruise at 2400 rpm for a trip you may see that your overall fuel burn may be 6.8 gph if you add the engine hours of the trip to fuel burn amount. Example: Start engine hour meter running, untie, leave harbor, allow engine to get up to temp, start to advance throttle, set cruise at 2400 rpm, slow for a few no wake areas..... you get the drift! Your overall fuel burn may be 6.8 gph. The best way to get true fuel burn for speed. Distance traveled divided by Engine hours ( start engine shut engine off) = average speed. Fuel used divided by average speed = mpg for that average mph Now you know mpg for a specific speed. Advance the boat to that speed and compare Speed to RPM.

Example: @ 9mph the fuel economy is 2.5mpg. Throttle the boat to 9 mph. what rpm is the engine running 1800 rpm ( hypothetical #) = 1800 rpm =2.5mpg , 9 miles in one hour divided by 2.5 mpg = 3.6 gph @ 1800 rpm this is not referring to fuel burn of the 210 cummins. Just an example.

This is a lot of information that most could careless, I know! But it is a good way to know accurate average fuel burn and know that your engine is maintaining it. You have a base line. When it comes to decided you have the right prop. The engine manufactures did that homework for you. The engine manufactures give you a max rpm for rated HP. The manufacture says the engine/boat is propped correctly if the engine can turn the max rpm preferably +150 rpm @ WOT. 210 Cummins anything above 2600 rpm when operated with full load and fuel. The boat and engine are propped correctly.