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Thread: Twin Yamaha 225s vs. Volvo Penta D6-370

  1. #1
    Member jrogers's Avatar
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    Default Twin Yamaha 225s vs. Volvo Penta D6-370

    This is a real scenario I would like to get some opinions on. I recently demoed a SeaWolf 30, and am considering getting one built. They have two power options, both costing the same amount, a Volvo Penta D6-370 or twin Yamaha 225s. It seems like the majority of the boats up here have outboards. I am interested in any opinions and if I am missing something.

    Volvo Penta D6 350HP (the new ones are 370HP, but the performance should be similar)
    Top speed 36 kts
    24.7kts 9gph = 2.74 kmph or 3.15 mpg
    27.3kts 10gph = 2.73 kmpg or 3.14 mpg
    200 Gallons = 680 mile range

    Pros:
    • Single motor for less things to go wrong. All information I have gotten on this motor is that it is very reliable.
    • Great fuel economy, and therefore great range and lower operating costs.
    • Some say that the inboard diesel rides better, since the weight is lower and farther forward.
    • Some complain about the smell and exhaust smoke. These common rail motors are amazing. They are relatively quiet, and I never even saw a puff of exhaust or smelled diesel fumes.


    Cons:
    • I noticed a slight vibration when turning, which I was told was the U-joints and this is normal
    • Single motor, so I would be relying on the 8HP kicker if there was a major failure. This in itself is not bad, but it only as a 9 gal tank for gasoline, so it would have limited return range unless you put a larger tank in, or carried extra gas. I have also hear that there are diesel kickers, but the only one I could find was a Yanmar that is no longer being manufactured.
    • Outdrive, risk of failures, leaks, etc.

    Twin Outboards 225 (These are from a Etecs. I think the Yamahas would be similar)
    Top speed 40+ kts
    28kts 17 gph 1.89 mpg
    200 gallons = 378 mile range
    Weight approximately 1100lbs less, could carry 150 gallons extra fuel, for a total range of 660 miles.

    Pros:
    • Redundant power source, although I dont think you could get on step with one motor.
    • Twin motors allow a bit better tight quarters handeling, but the VP duoprop outdrive is suppose to be really good, since it has dual counter rotating props.
    • No winterizing, at least on the motors, although the water and other systems on the boat would still have to be winterized.
    • Lighter weight, by about 1100 lbs (if I dont put a bunch more fuel on board for additional range.
    • Easier repairs and maintenance, and eventual replacement.

    Cons:
    • The mileage.
    • The motors in the way while fishing.
    • I want a rear helm station, and for this to work I would have to have electronic controls, which is a $7K option.

    Boat Use: This will be a personal use boat for me and my family, hopefully for many years. I want to be able to go to Seward, Homer and Whittier on occasion. I may want to go to Southeast at some point, but the main use would be weekend trips within 100 miles of port. The boat will be stored on a trailer.

    Any comments? Are the outboards easy access, redundancy and no winterization really worth the hit in fuel economy?

    Jim


  2. #2
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    Default Outboards!!!

    Tried the Volvo Diesels + Volvo Outdrives for 8 years. Switched to Outboards, totally love it, lot less hassles than diesels. Ran diesels on a daily bases during the charter season. My life is a lot easier with Outboards

  3. #3
    Member Sobie2's Avatar
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    Default

    I have to give the nod towards the diesel... RESALE is huge with a diesel. A lot of people who buy a used large aluminum boat are stretching the budget already and at least 50% fuel economy cannot be argued with. This is especially true since the boat costs the same. Also outboards while they can be rebuilt cheaply or powerheads swapped out have a shorter life span in 1000-1500 hours... generally speaking. I know charter guys with the D6 duoprop and they put on 1000hrs a summer and don't have problems.

    Lets hear CanCan weigh in on this issue... he has a big seawolfe with a diesel.

    Sobie2

  4. #4

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    One other thing to consider; if the boat is aluminum, will you consider beaching it? Outboards generally able to tilt above the hull bottom; also same thing if you get line(s) tangled in the prop; how do you plan to free them while at sea? Running your main motor with line in the prop typically results in prop shaft seal failure, which will allow seawater into the lower unit.
    At least with the outboards, you can tilt up and lean over the motor to work on getting lines free (just did this 2 weekends ago). Not a question of "if" but "when" this will happen. Vibration I don't believe is normal, and if they said it was u-joints, then I'd be suspect. I worked on 2 charter boats over the years with the older 200 hp Volvo diesels/IO's and the only vibrations we noticed was when something was wrong. Have they actually done a test to see if the single 250 would get the rig on plane? I don't know, outboards have come a long way since the "old" days. You also gain more interior room without the motor box. If going with the Volvo (expensive repairs), you should correct the kicker fuel issue; if you're not prepared to go the 100+ miles you mentioned with the kicker, then what's the point of the kicker?
    Hard decisions to be sure, but I'd love to have your problem!
    Good luck with rig no matter what motors you choose,
    Jim
    Last edited by Big Jim; 02-01-2008 at 09:45. Reason: spelling correction

  5. #5
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    You are forgetting costs. The diesel will give you approximately 60% greater fuel consumption but diesel is currently costing about $.40 a gallon more than gas.
    How much more (if any) is either of the motor packages? How many hours do you plan on boating a year?
    Every one has an opinion on this but it your money. My wife and I choose the I/O as we detest trying to fish off the back of the boat with huge outboards hanging off the back.
    If you choose the outboards will the boat have a heater you can use while running?
    I think the debate about beaching a boat is a non issue. Thats why we carry a zodiac.
    And this is just a speculation on my part but I do not see how that boat with twin 225's can average just under 2 mpg. 1.5 tops is more like it. And have you priced oil for the ETEC's? The good stuff is running 25-30 bucks a gallon.
    Tennessee

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    Member jrogers's Avatar
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    Default More details

    Thanks for the comments. I tried to get everything in the inital post, but I did forget some of the details:

    • There would be no motor box to contend with. The diesel would be completely below the cockpit. So this would not be an issue. One related this would be without the diesel, this area would be open to storage, althought there is a lot of storage on the boat already.
    • I would not beach the boat. I would carry a inflatable on the roof like Snowwolf suggests.
    • There is no purchase price difference between the twin 225 outboards and the D6 Diesel. If I wanted to get 250's, they would cost me about $3000 more. Also, if I want rear controls, then I need to have digital controls for the outboards, since the only Yamahas with these are the 350's at this point, and this is a $7000 option, which I belive is included with the D6 diesel.
    • I will add the fact that I cannot get a line out of the prop without entering the water a definate 'Con' to the diesels. I think changing a dinged prop while out would be the same situation.
    • I plan on running the boat about 100 hours per year, and hopefully I keep it forever and love it 15 years from now. It will not be chartered or used commercially.

    Jim

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    No brainer. If the price is the same I would opt for the diesel. Resale value would be much better, better fuel economy and longer running range.
    As usual, just my $.02's worth.
    Tennessee

  8. #8

    Default My 2 cents

    Been around Volvo's a lot, they are very fuel efficient and and for the most part very dependable but just like everything else they do have there problems. And thats when you wish you would have gone with the twins.

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    I'd go with the diesel for the same price. Buying ETec oil will make up for any difference in the cost difference between diesel and gas. If you go with the Yamaha's, I don't think you'll see the same fuel efficiency. I'd be willing to bet, the Etecs get better mileage... that's what we've seen with 225 Etecs vs. Honda 225's.

    If you ding the nibral props you'll be po'd. A set of props runs 1300 bucks.

    The vibration is the U-joint in the driveline and yes, I have felt it on every stern drive I've ever run... and the list is long. The fuel economy is a big plus with that boat. Pushing 11,000 lbs at 25 knots and getting better than 3 miles per gallon is about what my buddy gets in a 4,000 lb Hewescraft with a 150 Yamaha... But, you are moving alot bigger slab through the water.

    Resale is a factor, the diesels will certainly hold their value. If you decide you don't like the engine, sell it to me

  10. #10

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    You forgot to mention that OBs last 1000 hours, diesel inboards last 10,000 hours.

    Can you add hydraulics, another alternator, or a belt drive bilge pump to an outboard?

    Gots to go with Snowwolfe on this one ...


    On the "Steering flutter", do both boats have the same steering system? Most 30' diesel inboards steer via a rudder, while most OB boats steer the engine(s).
    Everything's different.
    Flutter is likely the irregular flow of water over the rudder being fed back through the steering, but it could be a problem with the check valves in a hydraulic system.
    ?

  11. #11
    Member jeff p's Avatar
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    Default Volvo

    I dont get over here on the power boat forum much but I am a Volvo dealer here in Mi on the great lakes. The volvo package is a very relaible unit, motor & drive are both solid. Maintain the drive well & you should get the service you are asking for without much trouble. I also sell O/B's as well so no real biased here. A boat with a single diesel should give you great results without having 2 units to maintain & without the O/B's hanging off the back. I would recommend you try both out if you can, the feeling of having the diesel torque as you climb & push thru rough seas should not be overlooked as they really just power right thru it.
    As far as running on step, you will not get on plane with one O/B & if you push it very long you will destroy the thing trying. The volvo drive really isnt leak prone most of the sealing is on machined surfaces with o rings & is pretty leakproof. If you can solve the kicker thing i think the volvo power is a no brainer.

  12. #12

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    Modern outboards last more than 1000 hrs. Can you get by with a single yam 350?

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    In my mind, twin engines are not useful unless the boat will plane on one of the two engines. If it won't, then you are better served by running a single and a substantial kicker. Reason: hull speed is hull speed - no reason to burn up the second motor pushing a giant bow wave at 10-12 mph when you can run a 15-25 hp kicker at hull speed of 7-8 mph.

    If you plan to do any trolling, mooching, or controlled drifting, you'll appreciate a good kicker with either a remote helm station in the cockpit or a tiller control. Don't fool around with the TR1s and whatever autopilots are available - they only work for trolling, and offer zero control when backing into a breeze to control drift speed.

    Regarding your choice in diesel engines, bear in mind that VP is squeezing 370hp out of an engine with less than 6L displacement. That's pushing it pretty **** hard. If you peruse the VP website, you'll notice that the same engines are programmed or configured to make different horsepower, depending on intended usage. The top rating of 370hp probably applies only to pleasure boats with no intended commercial usage, and anticipated engine life drops accordingly. What exactly the life will be is anyone's guess, but it's less than the same motor rated at 250hp, that's for **** sure, regardless of whether you feel you "run it hard" or not.

    Bottom line: no free lunch.

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    Default Diesel fan

    If you can get 27.3 knots @10 gallons an hour in aboat that size that is great. I get about a gallon less with the 260 d4 at that speed with an overall weight of about 8000lbs.
    I have yet to see any smoke from my diesel and the exhaust smell has not been a factor. I have the dual station controls and it was about a 1200-1500 upgrade.
    The hot water and cab heat from the engine is a nice bonus. One draw back I have is idle speed. When I 'm in gear idling I go about 5-6 knts.

  15. #15
    Member jrogers's Avatar
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    I don't think the boat would perform well with a single F350 Yamaha. I have been looking, and I cannot see where they quote towque anywhere, but the D6-370 is somewhere around 650 ft lbs of torque which I am sure the gas outboard would not be close to. As for the longevity of the D6,-370, it is a pretty new motor, so who knows, but they have also come out with a 435HP version of this motor, so VP seems to think is still has some performance, although I do agree that the higher you go in HP on the same block, the lower I think you can assume the engine life will be.

    On another note, I tried to lay out a plausable weekend trip and how the fuel bill would play out. I am starting to lean more towards the diesel, whereas I started out convinced that I wanted a pair or big outboards.

    Fuel price is higher with diesel, and fuel is only a percentage of the cost of a trip. Here is a theoretical weekend trip out of Whittier:

    Other costs:
    Tunnel $35
    Gas for truck: 8mpg * 100mi roundtrip @ $3/gal = $40
    Boat launch $15
    Subtotal: $90

    Diesel fuel for 150miles of running (75 miles out and back @ 3.3/gal): $158
    Gas for 150 miles of running (75 miles out and back @ $3/gal): $238

    Total gas weekend cost: $328
    Total diesel weekend cost: $248

    These are using todays fuel prices. I think they will just go up. Not hauling the boat each weekend would save on the truck gas cost as well as the tunnel cost.


    Jim

  16. #16

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    There is a test of a North River 28- Yam 350 on the yamaha performance website. It might be a similar boat.

  17. #17
    Sponsor potbuilder's Avatar
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    Who's gonna work on that D-6 if you have problems?? Don't think anyone in anchorage knows anything about them(or would i trust them to know.)

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    Default AK Volvo repairs

    Noah Marine in Anchorage can work on it, and there is a dealer in Seward that is well thought of as well. I cannot recall their name, but they were recently a Seasport dealer. It is a good question though. I would be interested in any feedback people have on local dealers. You can PM me if you don't want to say it publically.

    Jim

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    Quote Originally Posted by jrogers View Post
    Noah Marine in Anchorage can work on it, and there is a dealer in Seward that is well thought of as well. I cannot recall their name, but they were recently a Seasport dealer. It is a good question though. I would be interested in any feedback people have on local dealers. You can PM me if you don't want to say it publically.

    Jim
    Yeah they know what they are do'in

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    Default Diesels All the Way!

    I haven't heard anyone mention the safety advantage of diesels. Nothing like a gas bomb in your bilge to make your day!

    In pleasure service, the diesel will rust away before you wear them out. Just keep the fuel very clean and be religious about changing the oil with high quality oil like Delo 400 and you'll just have to worry about the normal things that wear out like salt water pump, starter and alternator.

    Good luck and fair seas to you no matter what you get.

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