Cutwater 26 - D3 220

[jboland11]

I have a Cutwater 26 with a D3 220. Actual WOT is 4120 RPM, specs are WOT 4000 RPM. I put on about 100 hours a year.

I regularly run at 3600 RPM and performance is good. At 3700 performance is very good with improved speed and fuel economy. Is 3700 too fast?

Thanks.

 

[Kim and Ed]

I have the same D3 220hp engine in my 2016 R27 Classic with similar performance. I disscussed this with Ranger and they suggested I have the prop repitched slightly to bring the WOT rpm down to 4000. Having done so the rpms are down and top speed has remained the same 23.8 knots. Efficiency has improved throughout the throttles range.
Ed/

 

[BB marine]

I also have a C26 with a D3 220 hp Volvo. I will post a few facts and a few opinions. Volvos recommendation for max rpm cruising is 10% of max recommended rpm.( 10% of 4000 rpm ). Max allowable RPM is 4130 RPM to 3900 RPM . WOT can be used for 1 hour total for every 10 hours of use. Not 1 hour each day. The longevity of the engine is approximately 3000 hours based on 300 hrs of WOT and 2700 hours at 85% to 20% of WOT.
10% of 4000rpm is 3600 rpm, the max continuous rpm recommended for the D3 is 3600rpm. (My opinion) I would not run higher then 3600 rpm for extended periods. If your propped to maintain 4120 RPM fully loaded Average passenger load in normal seas ( for your Area of boating) running at 3600 is acceptable. The D3 EVC does not show engine load ( if it does I can't figure out how to see it) I use fuel use as a base of engine load. At WOT I burn 12.0 gph Volvo rates the engine full load to burn 12.4 gph at 4130 and at 4000rpm 12.2 gph. Most diesel mechanics suggest( subject matter experts opinion) - small displacement, high speed, high rated hp diesels should be run at max cruise speed no higher then 70% of load and extreme would be 80% of load. At 3600 RPM our C26 burns 9 gallons an hour with a normal load, dingy on back. fuel water, 2 passengers, engine compartment temperature of 140 F , max WOT RPM 4030. This is slightly less then 80% of load but over 70%. When I am running light I can turn a max of 4130 rpm.( I feel comfortable At 3600 RPM Cruise.)

Propping the boat to turn a max of 4000 RPM must be done with the heaviest load you will have on board. Volvo does not want the engine to turn less then 3900 rpm. My opinion is you want the engine to turn Max of above 4000 rpm light load and no lower then 3900 RPM with the heaviest load you will cruise with. This is very important with a small displacement high output Diesel. Everytime we cruise I base my cruising speed on the load on the engine. If I open it up and turn 4130 I am comfortable cruising at 3600 RPM. If I have added passengers, dingy, full fuel, water, supplies and my Max is 3900 I drop my Cruising RPM down. If I see my compartment temperature above 135 F I drop down because of the power loss from high compartment temperatures. A boat engine is climbing a steep hill all the time. Add more weight and it is stressing the engine more. I believe( Opinion ) in propping a boat for the engine load not the speed of the boat.

Sorry for the long explanation to State my opinion, 3600rpm max. And be careful when pitching up. Having 4000 rpm for a max gives you very little room in rpm range when adding additional weight, passengers , and weather conditions. Anything less then 3900 rpm with a D3 ,Volvo does not recommend.

Our C26 WOT is 20 kts -23mph +/- 1mph, 3600rpm is 18 mph +/- 1mph ,We cruise at 3380 rpm 14 mph +/- 1mph
The addition of the custom Drop fins that I installed, added to making the cruise very comfortable at 14 mph bow stays at a at a good attitude , hull spray comes out just in front of the Hull step. Fuel economy averages 1.8 mpg at 8.1 GPH. Any speed above this fuel economy 1.8 mpg is the same we just go faster.

Cruising at 3370 rpm

 

[TBates]

Hello jboland11,

As noted by Brian, Volvo recommends staying below 90% of wide open throttle for any extended periods of time. Based on the numbers you've provided, 3700 would be still below the 90% mark. If the boat is heavier than normal, and you cannot reach the RPM's you can with a light load, you'll need to adjust accordingly.

Thank you,

-Tim

 

[jboland11]

Thank you all so much for the help. I'm going to give this a try on Saturday to try at 3600 to 3700. Thanks.

 

[MsChief]

Brian
That is very useful info. Thanks for sharing. I’m surprised by your engine temps at cruise rpm. At 3400 rpm my temps are 170 to 180 degrees. And that’s with full coolant tank. I wonder if something is wrong. I also have the Cutwater 26 w D220. I’ll have to ask the factory guys when I get to Roche Harbor next week.

Laura
MsChief Cutwater 26.

 

[knotflying]

Brian made ventilation modifications to his engine compartment, hence his lower temperatures.

 

[BB marine]

Brian
That is very useful info. Thanks for sharing. I’m surprised by your engine temps at cruise rpm. At 3400 rpm my temps are 170 to 180 degrees. And that’s with full coolant tank. I wonder if something is wrong. I also have the Cutwater 26 w D220. I’ll have to ask the factory guys when I get to Roche Harbor next week.

Laura
MsChief Cutwater 26.

The posted temperatures that are referred to in my post are related to engine compartment temperatures 140 degrees F to 150 degrees F. The C26 has a very tight engine installation much different from the other models that use the D3. R25 and R27. The Tugs have a full open compartment for the install. Open the hatch on a 25 or 27 Tug and the engine is exposed in a open compartment. Open the engine hatch on a C26 and this is what you see. Most of the engine is installed under the deck in a very confined area. The area shown in the picture(open area near electronics and reverse gear) stays 20 degrees cooler then the area where the engine air intake is. Maintaining 120 degees F to 130 degrees F with the use of my added compartment exhaust fan and 4" vent installed on the port side. This is marginally expectable to ABYC and VOLVO specs.


The intake areas higher compartment temperatures concern me ( 140F to 150F+ ) because of realized performance issues, and opinions given to me by the local Volvo Dealer, the regional Volvo Rep, the phone technicians at Volvo that the Dealer spoke to, and a Volvo Rep that assists Cruiser Yachts in Volvo engine installations that the dealer I am consulting with, works with. All have stated they have concerns that performance will be effected because of elevated intake temperatures. Fluid Motion technicians disagree and claim the high temps are fine. One positive I have found out from Volvo is the higher compartment temperatures will not effect the longevity of the mechanical components of the engine. The negative aspect is the longevity of electrical components, sensors ,relays, alternator, and common rail electrical components "could be" (opinion) compromised . Exact quote fromTechnical Support - GC
Volvo Penta of the Americas
1300 Volvo Penta Drive
Chesapeake, VA 23320 "If those values are correct, it is out of our recommendation and is not possible to predict what could happen.The engine must work according to our measurements and recommendation." " Engine installation Manual has specs and they need to be followed"
This picture shows the area of concern. The step that is removed is completely layered with insulation for sound deadening. The step coverers the area where the intake and turbo are located. There is heat generated in this area from exhaust manifold and turbo and the only way to dispose of the heat is through the engine.




This picture shows where the highest concentration of heat is . There is no ventilation at all in this area. I have recorded temperatures of 152 F in this area after a 4 hour run at 3400rpm, While running I periodically opening the deck hatch in the pilot house to allow cooler air into the compartment also running the blower.

There are pictures of the ventilation modification that I did last year in my album. I will make more modifications this year to try to get the compartment temperature at Volvos specifications for the D3 and to meet the ABYC specifications.



The temperature that I believe you are talking about is the engine Coolant temperature. At 3400 rpm my engine coolant temperature is right at 180 degrees F + 3 F if sea water temperatures are warmer. If this is what you are referring to Coolant temperature of 170 F to 180 F that should be fine. I would suspect closer to 180F. If you are referring to compartment temperatures at 170 to 180 I would be very concerned and I would ask them about that at Roche Harbor next week.