WOT?

[BB marine]

Brian: I really like this D4-300. It has plenty of grunt and it can provide a good sudden felt thrust forward when called for.... Oh and it's nicely and unbelievably quiet IMO with the excellent hatch sound insulation. Apart from the fwd end of the engine's belt location it has plenty of access for maintenance.... Oh, and I like the large oil retrieval pipe/tube on its starboard side for extracting the old oil rather than using the dip stick tube. It's just a very nice performing engine for my size boat.

Barry, I'm in full agreement. I think all the Volvo products are well designed engines. I really like the D3 which is a small displacement 2.4 L 150 HP, 200 and 220 hp engine that has a great deal of torque for its size and really packs some punch when putting the throttle down. The D4 even more with more displacement. My point was respect what they are. Realize the engines Displacement to Hp ratio and don't over prop it. If anything slightly under prop it. The Ranger Tugs and Cutwaters inboard diesels are not known to be fast planing hulls they are fast semi-displacement hulls. If the boats can run at 15kts to 20 Kts comfortably without over working the diesel power plant, running the diesel at no more than 70% load the engine selection for boat design gets a A+. Regardless of what rpm you run at 1300 rpm or 3000 rpm the engine should turn at or above Volvo's recommended max RPM D4 3500 ,D3 150hp 3000,D3 200,220hp 4000. I personally agree with many diesel mechanics that 2% to 3% above max rpm is optimal for engine longevity. The marine engine is in "overdrive" (comparison to a car or truck) all the time. It doesn't down shift to reduce load. The only way to down shift is to prop it correctly based on your Max RPM.

 

[Salty7]

Brian, your explanation on this subject is spot on. I would like to add the same process applies to all the engines which have ever been installed in these boats, be they Cummins, Yanmar or Volvo. They are all in the same category of engine, light duty diesel for recreational use. These engines will do a great job and last a long time if they are operated correctly, on their fuel curve and not over propped. I completely agree, the optimum prop is one which allows the engine to reach a speed slightly over maximum rated rpm with the boat fully loaded.

 

[PetDrs]

Great discussion!

My 2014 R21EC has the D1-30 and WOT is 3200 rpm which is exactly what it is rated for (not the 2-3% above as discussed here).

It also idles at 1100 rpm and I cannot adjust it any lower.... At idle in gear and in calm conditions it is moving at 2.5 to 3.0 knots! I bought it last summer and have not changed props or anything else, so as far as I know it still has the original prop. Does this mean it is over propped?

I plan to keep the boat for a long time and would like to try and maintain the engine the best I can. It likes to cruise at about 2700-2800 rpm and I run it at 3000 for a few minutes after idling a long time (trolling is an issue with the fast idle however).

The boat is going in for a service after the summer and I am going to ask them to try and address the fast idle situation.
I would greatly appreciate any and all comments from the community as to what they think.

Thank you
Jeff

 

[Automaticman865]

Brian,
You are truly on top of this and you also had a discussion about this on the forum back in Oct 20,2018.

This is also discussed in detail by Tony Athens of Seaboard Marine and he gets into the details of the engines and their longevity.
Take a look a John Deere and you will see that they have an M1 rating for some of their diesels. Its a 24/7 runtime at full power. But do the math they only get about 35 hp per liter, otherwise that rating changes quickly.
To run a Volvo d4-260/300 would be 3.7 x 35 =129.5 and using the 18 hp per gallon of diesel this you would not want to run
really over 7.2 gallons an hour to achieve superior longevity. Or running as a rule of thumb 2 gallons per liter.

Stuart

 

[BB marine]

Brian,
You are truly on top of this and you also had a discussion about this on the forum back in Oct 20,2018.

This is also discussed in detail by Tony Athens of Seaboard Marine and he gets into the details of the engines and their longevity.
Take a look a John Deere and you will see that they have an M1 rating for some of their diesels. Its a 24/7 runtime at full power. But do the math they only get about 35 hp per liter, otherwise that rating changes quickly.
To run a Volvo d4-260/300 would be 3.7 x 35 =129.5 and using the 18 hp per gallon of diesel this you would not want to run
really over 7.2 gallons an hour to achieve superior longevity. Or running as a rule of thumb 2 gallons per liter.

Stuart

I have read Tony Athens take on this subject. He is very conservative but knows a lot more about the subject than I do. He really pushes proper propping! I don't expect the D3 to be a 5000hr engine in the C26. I like to run it around 3400 rpm burning 8.4 GPH which is approx 70% load. Hopefully it will be a 2500 or 3000 hr engine. I actually have more hours running 2250 burning 2.8 gph than I do burning over 8gph so it should make that for me or the next owner. I never really thought about this with diesels until owning a high speed D3 .Diesels use to be big displacement and less HP. My dads boat was powered by a 80 Hp Lehman, 254 CI - 4.2L, 19 hp per liter. WOT was 2100. It was just getting broke in at 3000 hrs. It pushed a 29' Roughwater 9kts and cruised at 7kts 1.5 gph.

 

[Kaptajnen]

I asked a tech from Pacific Power Group (a company located in Kent, Wa that deals with all warranty work in Puget Sound for Volvo Diesel engines installed in Ranger Tugs) about this issue as it relates to the D4-300 installed in my Ranger 31-S.

He explained that as long as I run the engine at 3000 RPM there is no need to go to WOT for 5 minutes at any time.
The only time that becomes necessary is if the engine is run at idle or low RPM (1500 RPM or below). Then the turbo will start leaking fuel and the engine will be stressed.

And of course, the fuel consumption ( around 1.4 NM per gallon) in my boat is the same, whether I run it at 8 knots or 18 knots - so why go slowly?

 

[Cutwater28GG]

should I reprop?

WOT RPM is 3340 on a cutwater 28. d4-260

i have slime on the bottom and am a little heavy.

 

[baz]

I asked a tech from Pacific Power Group (a company located in Kent, Wa that deals with all warranty work in Puget Sound for Volvo Diesel engines installed in Ranger Tugs) about this issue as it relates to the D4-300 installed in my Ranger 31-S.

He explained that as long as I run the engine at 3000 RPM there is no need to go to WOT for 5 minutes at any time.
The only time that becomes necessary is if the engine is run at idle or low RPM (1500 RPM or below). Then the turbo will start leaking fuel and the engine will be stressed.

And of course, the fuel consumption ( around 1.4 NM per gallon) in my boat is the same, whether I run it at 8 knots or 18 knots - so why go slowly?

I have the Volvo Low Speed feature installed on my 2019 R29 CB NW Edition and I utilize the Low Speed for many hrs trolling for fish. When the Low Speed is engaged the engine runs at 700 RPM all the time regardless of my low trolling speeds of 1.5 to 3.5 kts. The prop engine RPM to prop shaft RPM is 2:1. Thus at engine 700 RPM the prop shaft turns at 350 RPM when the transmission clutch plates are firmly engaged.

After trolling for several hrs (could be 3 or 4 hrs at a stretch) and returning to home port I always run the engine up to around 3000 or higher for a few minutes and long before I reach my marina's entrance as I like to enter slowly and avoid large wakes for other boats in the vicinity.

So far I see no evidence (fingers and toes crossed) of the turbo being stress or leaking fuel, oil or exhaust residues.

My ONLY concern is the wear and tear on the clutch plates as the Low Speed EVC software and hardware means the hydraulic valves used for engaging the clutch plates results in the prop shaft's plate slipping on the direct engine's output plate to accommodate lowering the prop shaft's RPM; hence low speeds (that is 350 RPM and lower) being attained.

 

[Kaptajnen]

Two different boats ...your Cutwater 29 and my Ranger 31-S.

Sort of an Apples and Oranges comparison as far as the WOT issues.

 

[baz]

Two different boats ...your Cutwater 29 and my Ranger 31-S.

Sort of an Apples and Oranges comparison as far as the WOT issues.

Not so, I have to say. Mine is a 2019 R29 CB and yours is a R31 S. Both have the same Volvo engine.

 

[BB marine]

The only time that becomes necessary is if the engine is run at idle or low RPM (1500 RPM or below). Then the turbo will start leaking fuel and the engine will be stressed.

I'm somewhat surprised by the Technicians explanation. From what I have been told throttling up periodically is a good idea to keep the soot deposits from building up on the turbo's turbine wheel (exhaust side).I agree that running 3000 rpm does that. The D4 does not have a VGT turbo so there is no need to worry about the vane plate getting exhaust deposit buildup and sticking like the D3 or other diesel engines with VGT. The newer common rail diesels burn much cleaner than the mechanical injected diesels. I question how does running at lower rpm cause the turbo to leak diesel fuel? How does that much diesel fuel get to the turbo to cause it to leak? The diesel fuel is injected into the cylinder and combusted. A common rail diesel should be able to run at any lower RPM without issue as long as the engine is coming up to operating temperature and in gear under a load. The stresses on the engine are greater at 3000 rpm than 1500 rpm.If the engine is run at low rpm in gear under load for an extended period of time it is a good idea to run it up for a few minutes to bring the operating temperature to the higher end getting the oil heated up to help dissipate moisture and to elevate exhaust temperature to help clean exhaust deposits. I agree with the Technician if your running all day long at 3000rpm you don't have to worry about running it any higher. The only reason to throttle up to wot is to confirm you can turn recommended wot rpm. I'm not saying the technician is wrong, but I have never heard that running lower rpm causes the turbo to leak fuel and stresses out the engine?

 

[Kaptajnen]

I am paraphrasing his explanation of what happens when the engine is running at low rpm and the turbo is not able to work efficiently. But I am not a technician so I will defer to you in this matter.

 

[BB marine]

should I reprop?

WOT RPM is 3340 on a cutwater 28. d4-260

i have slime on the bottom and am a little heavy.

Gavin, if your RPM has dropped from recommended WOT of 3500+ to 3340 and it could be because of bottom fouling I would not change the prop pitch or change prop. Clean the bottom. If your normal rpm is below 3500RPM WOT, clean bottom and equipped heavy like most of us do. I would consider getting your prop tuned. If I was propping a D4 260 or 300 I want it propped to turn 3580 to 3620 with average load, 3650 rpm when lightly loaded (governor). The reason for this is (I'm loaded heavy for a trip),( I have extra passengers onboard extra coolers,,,,,) (I have some bottom fouling)(I make a bad judgement call and I'm running in disturbed sea's and wind) Under any of these conditions the engine is put under more load. If your rpm margins are already used up before these conditions, you are really lugging the engine down. Thats not good for any diesel engine and definitely not good for 70 hp per liter engine. I know of a Cutwater 28 that turned close to the same rpm as you are stating. The owner talked to Acme props, stated his rpm numbers and acme recommended dropping 2" of pitch. He had his original equipped prop re-pitched dropping 2" of pitch. The boat fully loaded ( actually loaded to cruise to Alaska) He still was able to turn over 3500rpm. When unloaded and operating a light boat he turns 3630 rpm. He lost no noticeable speed after dropping 2" pitch but the engine is operating in the correct rpm range. I would be interested to see the Fluid Motion Sea trial of the C28. I would suspect it was not propped to turn 3500 +rpm. I have talked to several C28 owners that are seeing numbers like yours, none have turned 3500 rpm. Many boat owners say "I don't run the boat at high rpm so it doesn't matter. If you operate the engine at 20% load or under they are probably correct. Higher than 50% load it does. The design of the Rangers and Cutwaters is you either cruise at 20% load or above 50% because anything in between is inefficient. My opinion is it matters.

 

[Cutwater28GG]

thanks Brian. I think the only day I saw 3500 was on the test trip before purchase when the boat was basically empty: half tank fuel. no gear, no water, two people.

the divers are out this week for zincs and clean and i will pull some weight off the boat and see what happens first. thanks for the insights.

 

[Automaticman865]

Gavin,
My CW28 could not reach 3500 when new. Have the Volvo tech on board, best was 3300, usual loading etc...
Dropped the pitch 19 x 23 to 19 x 21, 2 inches.
Now beginning of each season starts out(june) wot around 36++ and on sep 5 I was able to get wot 3500 (but nothing more) with all the usual growth and slime. It will be coming out of the water in about 3 weeks so the two inch drop was perfect in this case.
Stuart

 

[Cutwater28GG]

interesting thanks Stuart. can you get 18 knots at 3000 with this prop? what speed is 3500 (averaged)?

 

[Automaticman865]

Gavin,
I put my super memory to work (well ok, its my cellphone.)
I take a group of pics of my garmin at all different speeds to be able to look back and see what the engine was doing. That and sending an oil sample each year makes a much better record of things.
Back on Sep 5 3000 rpm 14.9 kts, 3500 rpm 20.7 kts. Also I like to stick to the roughly 2 gallons per liter, or 35 hp per liter which equates to roughtly 7.2 - 7.4 gallons an hour, so I cruise a lot at 2650 rpm 12.2 kts 7.3 gal/hr.
Stuart

 

[Cutwater28GG]

Interesting data.

Depending on currents I’m somewhere between 16-18 knots at 3030-3050 Rpm. This is about 10.5 gals per hour or 1.7Nmpg I’m at 21knots at 3300rpm

I really don’t see the benefit of cruising between 8 and 18 knots as the Nmpg is the same or in some cases worse!. I might as well get to the destination or slow down to 6 knots. Ie get properly up into the plane or go displacement hull speeds.

 

[baz]

Interesting data.

Depending on currents I’m somewhere between 16-18 knots at 3030-3050 Rpm. This is about 10.5 gals per hour or 1.7Nmpg I’m at 21knots at 3300rpm

I really don’t see the benefit of cruising between 8 and 18 knots as the Nmpg is the same or in some cases worse!. I might as well get to the destination or slow down to 6 knots. Ie get properly up into the plane or go displacement hull speeds.

I agree.... it's good to have the choice of speeds.

 

[BB marine]

Interesting data.

Depending on currents I’m somewhere between 16-18 knots at 3030-3050 Rpm. This is about 10.5 gals per hour or 1.7Nmpg I’m at 21knots at 3300rpm

I really don’t see the benefit of cruising between 8 and 18 knots as the Nmpg is the same or in some cases worse!. I might as well get to the destination or slow down to 6 knots. Ie get properly up into the plane or go displacement hull speeds.

You have to look at the big picture when propping properly. The object is to get the best possible performance pushing the boat and best possible recommended Max Rpm to preserve longevity of the engine. If you are turning a 19 X 23 pitch and pitch down to a 21" you will not see the same speed at 3000 rpm. ( theoretically you are traveling 2" less per revolution of the prop) What you will see is less load on the engine and slightly less GPH, MPG probably the same. If you are 21knot at 3300rpm WOT and reduce pitch 2" and now turn 3550 to 3600 rpm your WOT. The boat speed should be very close to your WOT of 3300rpm but you have put the engine in the proper load range that Volvo has designed the engine to run at throughout the full rpm range. If you are not that concerned about longevity and just speed don't re-pitch. If you are looking for best performance for the boat without sacrificing the longevity of the engine. Prop the boat so the engine can maintain 3500rpm +2%.

Also I like to stick to the roughly 2 gallons per liter, or 35 hp per liter which equates to roughtly 7.2 - 7.4 gallons an hour, so I cruise a lot at 2650 rpm 12.2 kts 7.3 gal/hr.
Stuart

This is the recommended max fuel consumption per liter to conserve longevity of the engine. The semi- displacement hull is very efficient while cruising hull speed. To get it to " Plane" takes a lot of HP. A C28 with 260hp needs 80% of that HP to
plane burning almost 3 gph per liter. Now do that to an engine that can't turn max recommended RPM. In the world of high speed small displacement diesels this is not a good equation. Most boat owners don't care as long as it starts, shifts, and runs. Automaticman has the right idea. Propped conservatively, runs it conservatively, but still has the option to run hard staying at or above Volvo's recommendation . Cudo's