Yanmar 315's vs. 370's in SF

Brian Davin · Post by **Brian Davin** » Wed Sep 28, 2005 1:35 pm

I spoke with Mack Boring (Yanmar Distributor) at the Norwalk Boat Show who put me in touch with an owner who repowered with Yanmar 315's. I contacted Art M., the boat owner, who also owns a small boatyard in Mattapoisett, MA. He has a 1987 SF that he repowered with yanmar 315's. He's very happy with them: - He cruises typically at 22 knots (loaded) at 3100 rpm - Yanmar has told him he can cruise at 3500 rpm, which results in 25 knots, but he likes to run conservative (22 knots) for increased engine life... He only burns 10 gallons per hour at 22 knots, WOW! - Top end is close to 30 knots at 3800 rpm His feedback was two fold: 1. He didn't go with 370's because he would have had to cut some engine compartment fiberglass to get the engines in the SF 2. If he had to do it again, he would have put the 370's in for the improved performance ... He said the boat performs very well in the 25 knot plus range, even pushing through a good chop. The debate continues! I'm still trying to get hold of the 1977 33' FBC owner in Old Saybrook who repowered with 370's. If I'm able to make contact, I'll share his feedback. Brian '90 Bertram 33' FBC Never Say Never Westbrook, CT

franklyprice · Post by **franklyprice** » Wed Sep 28, 2005 3:22 pm

Brian, I met the same guy when I was in Mattapoisett last summer. They were very gracious and let us look at their boat . It really looks nice to see those in the engine bays. The fuel burn he is giving is only half the real number. He told me 9 gallons an hour at that speed but that is simply impossible, even Yanmar will spec those engines at around 10 gallons an hour at cruise, EACH. Still a very respectable number, by the way. One other reason I'd consider the 370's instead of the 315's in Yanmars would be that the 370's are the next size bigger engine bock size and that is the lower HP rating of that series , so would probably be a bit tougher and longer lasting. Frank Price

Brian Davin · Post by **Brian Davin** » Wed Sep 28, 2005 4:24 pm

I thought that fuel consumption was too good to be true[:(] Great point on the 370's being the lower end of the series in terms of longevity, that is a plus. I also was thinking that if you're running at 70% vs. 80% of full throttle, economy would improve for that engine. Brian '90 Bertram 33' FBC Never Say Never Westbrook, CT

Sean B · Post by **Sean B** » Wed Sep 28, 2005 5:43 pm

quote:Originally posted by Brian Davin I also was thinking that if you're running at 70% vs. 80% of full throttle, economy would improve for that engine. Diesels don't work that way. They only burn as much fuel for whatever power they are generating, at any throttle position. Actually the "throttle" control on a diesel isn't a throttle at all, it's an RPM setting. It's definitely true what Frank said about them lasting longer though. Sean Burlingham "Island Time" 1987 Bertram 33 SF Melbourne, FL SBurlingham@cfl.rr.com

Post by **dougl33** » Thu Sep 29, 2005 4:19 am

quote:Originally posted by Brian Davin - - Yanmar has told him he can cruise at 3500 rpm, which results in 25 knots, but he likes to run conservative (22 knots) for increased engine life... He only burns 10 gallons per hour at 22 knots, WOW! I think this guy has got his information a little crossed. 1. According to Yanmar's spec sheets, the engine is only rated for 3800rpms. I doubt very much that Yanmar has told him he cruise the boat 3500rpms as that's 92% of WOT![:0] I know you can run diesels hard, but no diesel manufacturer in the world is going to tell you to run them at 92% of WOT. 80% definately, 85% for a fast cruise, 90% for a short period of time, but not 92%. Its a myth that all diesel like to be run 200 off the top. Sure you could do it, but you'd be looking at a severely reduced life expectancy. I don't think running them at 3100rpms (81.5% of WOT), is running them that conservatively, however I do think he'll get many trouble free hours at that rpm. 2. Again according to Yanmars own spec sheet, the 315hp motor burns approx 9 gph at 3100 rpms. Thats a total of 18gph, which is still outstanding. Assuming a useable total fuel amount of 283.5 gallons (90% of 315 gallons), that would give Brian a cruising range of just under 350 miles (about 16 hours of running time). I figure that's about double what he's getting right now (assuming 30gph at 18.5 knots, which equals 175 miles and just under 9.5 hours of running time). http://www.yanmarmarine.com/products/pd ... chData.pdf Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA

jav · Post by **jav** » Thu Sep 29, 2005 8:11 am

Doug, I don't mean to disagree with you and, I would have agreed with you a year ago but I've been somewhat corrected. I frequent boatdiesel.com, know many of the folks at Mac Boring and recently attended a diesel engine seminar put on by Volvo. 4 Volvo authorized dealers were represented and there was much disussion about how you can/should run modern diesels. My understanding was the same as yours and as it turns out, it was incorrect. Now, I can't swear that Yanmars spec is the same as Volvo's but in fact, Volvo does allow continuous running at more than 92% on pleasure duty diesel engines. The spec that is published (and that I think you referred to) 10-20% below max actually refers to the max the engine can be run at AFTER some specified time at WOT. This sounded dead wrong to me and I argued the point with allot of support from other attendees! The factory boys were all in agreement that IF, an engine reaches at least maximum rated WOT at a given load, then that engine can be run at 200 RPM off the top all day long... AS LONG AS it never goes above that load. The moment the engine is loaded beyond that point(approaching WOT), then the 10% below max applies for a specified amount of time. I still struggle with this but if you search boatdiesel.com,there are a couple of threads about this, the experts seem to disagree with us. Also, and for what its worth, I have a freind with an Albin 28 with the Yanmar 315. His boat is much lighter than the Bert 33...(weighs just under 5 tons loaded)... but its a single engine boat. He uses the crap out of the boat (over 150 hours a year)and keeps meticulous logs. He typically runs the Yanmars at 3000-3200 RPM and his average fuel burn for this and last season was under 5 GPH! I've known him for over 20 years, work with him every day and I know this number to be accurate (becuase before he bought the boat, I pretty much called the dealer a liar for suggesting he should expect that from the boat). While I still don;t beleive thats the consumption at cruise, it's certainly not what Yanmar publishes in the graphs either. Those graphs are generated based on a theoreticla prop demand curve that closely matches the engines peak torque curve. Most applications are not loading the engine anywhere near the maximum torque curve other than @ WOT. Since I know the majority of my freinds hours are at cruise, the 5 GPH average makes sense. Working the numbers forward to a Bert 33 with twin 315's running at 3100 RPM, the guy may not be far off if thats an "average" burn rate versus a "cruise" burn rate.

Post by **dougl33** » Thu Sep 29, 2005 8:28 am

Jav, I see what you're saying, but I guess it all depends on whom you read/listen to on boatdiesel as I've spent some time over there as well. I've seen a lot of debate/discussion (some from Tony Athens himself) suggesting that the 200 off the top rule was a load of crap. I guess it all depends on the setup, engine, etc... Also, avg fuel burn and fuel burn at cruising speed are 2 completely different animals. My avg fuel burn for the 4 seasons I've run my boat is 20gph (340hp 454 Mercs). But we know from the flowscan guys that at cruising rpms the boat is burning 30gph (+/- one or two gals). Is your friend figuring the 5gph simply by taking his fuel consumed over his total hours (which really isn't that accurate) or is he using a fuel monitoring system like flowscan or navman to pinpoint usage at a given rpm? Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA

jav · Post by **jav** » Thu Sep 29, 2005 9:11 am

Doug, my friend does not have flow scans and is dividing total fuel by total hours. I agree, this is not an accurate indicator of cruise consumption but, with close to 400 hours, over 1500 gallons of fuel and a reasonable understanding of how the boat is run, I am very confident that he's not burning 9 GPH at cruise either. Is it 5 GPH at cruise? I don't believe so. But, it is under 5 GPH average... was the Bert 33 owner with the Yanmars stating flow scan numbers at cruise or just what he precieved based on fuel used? I used to have this debate on my dock all the time when I had flow scans on my gas engines. Guys with the same boat as me would argue that there was something wrong with my boay cuz they were burning 15 GPH at cruise when my flow scan was showing 22-24 GPH at the same speed. They didn't have flow scans so they would could only guess based on their average but I believe my guages were right. Your absolutlely right about "who you listen to". For years it was beat into me that the 200 off the top is bull... don't do it! OK, I'll bite.. far-be-it for me to spend good money on diesels only to kill then with stupidity. Then you get into a room full of "experts" and factory representatives and they reverse everything they've tried to beat into you! I don't mind telling you I was a little confused and to be honest, angry! I read voraciously and go overboard to learn and protect my investment. Things got a little heated as I felt I was either misled before, or being misled now...which is it? The answer that we got was that the engines are designed to run safely 200 RPM off maximum attained RPM ( not even max rated, but max attained). So that means in my case where my engines reach 3850 even though they are rated at 3800, I can run at 3650 all day long. Of course if the engines can could only reach 3600, though rated for 3800, then your max would be 3400... but your engines would be overlaoded becuase they could not reach rated RPM. There was a pretty big BUT though. All of this presumes a "by the book" installation (which many dealers don't do), it presumes meticulous maintenance (which many dealer/operators don't do) and it presumes a consciensous, alert operator, (which many captians are not). For the average Joe that can afford a diesel boat, the 200 off the top should NOT be advised becuase of all the possible issues listed above. BUT, for those attending the seminar, that are serious about about caring for their engines... absolutely the engines can be run that way safely. Either that or they just want you to blow up your engines and buy more??? At times its hard to know who to believe. As I said, I operate my engines the old way, 90% or less. I used to think that was safe, but close to pushing them a little. Now, I just think I'm babying them a little more and I can live with that.

Post by **dougl33** » Thu Sep 29, 2005 9:31 am

John, As is usually the case, its not always easy to know the right thing to do! Sounds like you're trying to err on the side of caution though, which is smart as I'm sure the re-power wasn't cheap. I don't know if the gentleman in Mattapoisett has flowscans or not. Brian and Frank have spoken with him, but I have not. Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA

Brian Davin · Post by **Brian Davin** » Thu Sep 29, 2005 1:09 pm

Doug, I unfortunately didn't ask the guy if he had flowscans [:(] If I happen to speak with him again, I'll definitely inquire. By the way, thanks for all the education, diesels are a whole new animal for me to learn about. Brian '90 Bertram 33' FBC Never Say Never Westbrook, CT

GMarty · Post by **GMarty** » Mon Oct 03, 2005 6:54 am

In my view, the notion of running her at 25 to 28 is a theoretical one - and the value associated with doing so should be greatly discounted - especailly in the north east. That is to say, you can hardly ever do it in reality so why make it a deciding factor. I would be surprised to hear people on this board say (honestly) that they can run 25 into a decent sea and be OK with it. I just don't buy it. I run the hell out of mine in all conditions and 18 to 20 is more in line with reality - and even then if it gets snotty you ain't running at 20 without taking a beating. You are also making these comparisons as if they cost the same - i think the difference is in the 10 grand range. As one who is about to pull the trigger on the 315s I sure hope my line of crap is right!

Sean B · Post by **Sean B** » Mon Oct 03, 2005 7:36 am

Down here in FLA a typical day is usually only 3-5 foot seas, less in summer, so I would think the extra power would get used often and worth considering. Even the Gulf Stream will stay that calm unless there is a northern component in the wind. Also a lot of time is spent in the intracoastal waterway which is always calm and the extra speed would definitely get used there. In my neck of the woods the Sheriff's simply won't pull over bigger boats so you can speed all day in the channel with impunity. By contrast, in Lauderdale area you can't get away with anything, will pull you over for spitting in the water. But I agree, if you can't use the power in your area, why have it. I'd be opting for the extra speed myself though. Sean Burlingham "Island Time" 1987 Bertram 33 SF Melbourne, FL SBurlingham@cfl.rr.com

GMarty · Post by **GMarty** » Mon Oct 03, 2005 8:40 am

So, your cruising at 25knots in 3 to 5 footers? I must be a big sissy cause in my experience 5 footers mean 16 to 18 knots - max.

jav · Post by **jav** » Mon Oct 03, 2005 9:13 am

GMarty, I love an honest man. Theres allot of weight in 3'-5' waves and I know you guys own Berts (and I only aspire to one day), but 25 knots into 3-5' is hard for us lesser folk to fathom. Having said that and knowing diesels pretty well, when I do get a Bert, I will put in the highest power diesels that will fit. With diesels, your consumption is determined by the power "used" not the power "available" (as long as the wieght is the same). As an example, If one were to compare 2 identical B33's, one with twin Cummins 6BT 210 hp engines, the other with Cummins 6BT 375 hp engines, the consumption should be the same (speed for speed) for both boats at any speed they can "both" achieve. The one with more power will have the option to far exceed the max speed of the lower powered boat, and thus consume much more fuel but, thats an option the lesser powered captain just won't have. Price is an important consideration and in fact, with some of the newer electronic diesels, you pay for the "power", not for the "engine" . Thats becuase each engine within a family is the same and capable of every power level by software control alone. You can buy a 300 hp engine and later upgrade it to 375 hp and its only a software change ( a very expensive software chanage... agian your paying for the power). A good option that I haven't seen discussed here is Cummins factory rebuilt engines. Especially with the new compliance laws coming into effect, I hear they are very attractively priced and for the most part, the same as new with exception of raw castings. I've not priced them but I heard about 60% of the cost of new so I'm thinking 10-14k per engine? BTW- I presume Yanmar 6lp -315 hp engines?? If so, that is a good choice also, decent power, excellent economy, quiet and almost no smoke. I'm jealous.

Rick · Post by **Rick** » Mon Oct 03, 2005 9:23 am

Brian, I met that guy too....we were both moored in Edgartown. I invited him to chat on the website and i thought he was going to bark...doesn't like computers too much I guess. Those 370 Yannies sound like a dream...anyone got $85,000 I can borrow ? Rick Ticket 85 SF Falmouth, MA