Sandro":qescdf6k said:
Dbsea .. just run where you like to run with you, guests and family. The engine will be fine for the amount for time you will own the boat. And will have hundreds even thousands of mile left for the next owner. These engines, even totally abused will run 2k hours. Easy. A Prior poster also made good point. All the other stuff will fail well before the engine itself. The engine itself, if used regularly, will outlive the boat. So just enjoy and don’t perseverate over a couple hundred RPM.
Sandro is spot on with some of his comment. These engines totally abused will run as much as 1500 to 2000 hours. For the weekend warrior boater that puts 50 to100 hours a year running it on the pins or running 80% load (3200rpm if properly propped) as a normal cruise speed. In ten years if well maintained the engine could still be a decent motor for the next owner. If you are a Sport Fish owner and want to get off shore in a hurry. Run them hard !! Many do and the life expectancy of these high speed diesel is cut short but that is the price to pay to play and many sport fish boat owners know this. They want big HP engines to run hard and fast. They are willing to spend the$$$ at 1500 or 2000 hours. So yes if you want to run the engine hard and follow Volvo's recommendation of continual rated operation at 90% of WOT or 80% load the engine will last at least long enough that Volvo will not be responsible to replace it. When you sell the the boat and the buyer knows the engines probably need to freshened up and this reflects the price of the boat. So yes enjoy the boat and run it hard and plan on spending some $$$ if you plan on keeping the boat or being up front with the future owners that you ran them hard.
I was at the marina this week ( home for a few days in the cold midwest) and in the shop was 4 D6 long blocks that were pulled from a two Prestige yachts. Two of the D6 had close to 3000 hours and two of them were at 1500 hours based on what the tech told me. Both boats had a history of running hard. The engines with 3000 hours, a boat that had the same captain for all 3000 hours, but ran the engines 3000+ rpm plus because he felt that is in his opinion where the boat performs and rides the best. It was a 2016 Prestige. Not a weekend warrior. The boat summered in the Midwest and ran south to Florida for winters. The engines both were down on compression and blowing oil. The total job for the engine refits with new long blocks and exchanger rebuilds plus parts and labor was just short of 100K. The engines with 1500 hours were in a boat also late model year 4 or 5 years old. Owned by a time share group. Several owners owned the boat and I assume have the same thought process as Sandro, run them hard and enjoy them! I believe they did. The engines too were low on compression, power, hard starting, burning oil and sooting up the transom. Based on the conversation I had with the technician. He said most of the bolt on components were good but he was replacing some of them for reliability purposes.
In talking to the service technician who I have known for years in fact I trained him when he was hired by the marina in 2000 as an apprentice from a vocational school. He said D4 and D6 engines have been very dependable and they have several customers with over 4000 hours on their engines and still running strong. Most of the boats that they service are larger planing hull boats that are powered with D6's. They do have some smaller mid 30' range with D4's. He said Volvo rates them at 80 % load for continual operation but the reality of that is the reduction of longevity. There are folks that don't care if the engines are going to wear out sooner they want to run hard and fast and know that comes with a price. He tells his customers 2500 to 2800 is were they like to run and will run there for many hours. Once again these are planing hulls unlike the Rangers and Cutwaters that are semi-displacement hull requiring a lot more power to push them at higher speeds. So 2800 is probably the rpm to zero in on. The D4 and D6 are the same engine design the D6 just has 2 more cylinders. 320 hp D4 3.7 L =86hp per liter and the D6= 79 hp per liter ( sports car engines) compared to what the commercial boats are using.
For the folks that want the power to push them through the water when they need to and cruise slower for the long haul the D4 and D6 engines will easily give 5000 hours and more if well maintained.
Based on what this thread is about "
How to Properly run with 435HP for longevity" Operating this 5.5 liter engine that is rated at 435hp which is 79 horse power per liter. Does not fall into the same category as the diesels of old that were 33 horse power per liter= 200 hp. You could you could run theses engines on the pins for 10,000 hours. You could run the D6 435 hp for 10,000 hours too if you ran them at 200 hp all day long.
So there may be several answers to this question based on what is thought to be longevity. If longevity is concidered 2000 hours. Run the engines to the pins and back off a couple hundred rpm. Let them "Sing"!! If longevity is getting the industry standard rating of 40 % average load of the operating life of the engine. Expecting 5000 hours, which many folks cruising the waters experience this. Be conservative and run the engines 2500 to 2800 rpm. You may get the chance to see the hour meter turn to 5K. If you don't the next owners of you boat will.
