Diesel vs. Twin Gas Outboards

[jrogers]

This is a real scenario I would like to get some opinions on. I recently demo’ed a SeaWolf 30’ (www.seawolfmarine.com in WA), and am considering getting one built. They have two power options, both costing the same amount, a Volvo Penta D6-370 or twin Yamaha 225’s. 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 Yamaha’s 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 don’t 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 don’t 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 Alaska on occasion. I may want to go to Southeast Alaska 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

[wbyrnes]

Diesel hands down

[junior34]

Diesel

[micky]

Diesel

[bob5292]

Those Seawollfs are very nice boats. What is the deadrise and width of the model your thinking about? I have a new 30' aluminum boat with dual D4's (that happens to be for sale). I spoke to Seawolf and they will put duals into a boat thats 10'6 wide. I am not sure how much more it would be to go with dual 260s vs the single 370 but it may be something to consider.

Bob

[Provie63]

I faced the same choices last year..got a lot of good advise from the THT faithful.. For me, cost of operation was a big consideration..Diesel won that one hands down.. Maintenance, cost was another..while it costs a bit more to service a diesel, it still not as much as 2 OB's.. One other "pro" to consider is the safety factor of diesel fuel..much less volatile than gas.. In my case, the redundancy factor of twins may not have been as big an issue as it may be for you..The waters I fish are far from desolate..There are always plenty of other boats, and Seatow on hand in case my engine quits..If I had been looking to set up a boat to make frequent runs to our offshore canyons, I would have likely leaned more toward twins.. I also concur on the lack of smoke and fumes emitted from these new engines.. My Cummins is virtually smoke and smell free..Best of luck with whatever you end up with !

[mronzo]

I love my twin outboards but for where you're boating
it would be ideal to be able to heat the cabin/cockpit.

How about a picture? Do they have a web site?

Get exactly what you want! With every option you WANT!


Good Luck!

[cave man]

I'm in a similar predicament. Am in the market for a 31 or larger Contender but that Tides express that is for sale on this forum has really caught my eye. Diesel is currently more expensive than gas so the higher mpg's may not be realized on a cost basis. Maintenance between a single diesel and twin 4 strokes is probably about the same both in cost and time. I only have one diesel motor in my truck and it has never let me down but te idea of twins when I'm at a rig 95 miles out sure is comforting. Great thread and I look forward to following it.

[cave man]

Those Seawolfs' are awesome. My buddy Erik Johnson has one called the Shiras with twin diesels and it is a real tank. Pretty sure the guy who owns the company makes every weld on the boat personally then farms out the finish work.

[Provie63]

cave man - 2/7/2008 5:37 PM
" Diesel is currently more expensive than gas so the higher mpg's may not be realized on a cost basis. " it.

This is an interesting point..Where I fish in NJ, last season when gas at the docks was running between 3.10-3.20 per gallon, diesel was 2.60-2.80.. Yet at land based stations diesel was always higher than gas.. I'm not sure why, but someone told me it was due to "road tax".. anyone know if this is true?

[narcisodc]

Interesting discussion. I have had twin mercury outboards on my previous boat and they were good, maintenance was not that expensive (water pumps every two years, filters, winterization, etc = 2000 year which was a couple of years ago). Fuel was not that bad considering we usually ran only 20 to 40 miles offshore and these were mercury optimax's which are great on fuel and gas prices were a little different. I now have a 32 Blackfin with twin 300 hp Cummins diesels and now travel 60 to 100 miles per trip. We have had this boat for a couple of years and usually put 200 hours a year on the engines. The maintenance I think is close to the maintenance of the outboard. Oil changes of engine and transmission oils and filters for primary and secondary filters usually two times a year, impellers every year and winterization costs me $2500 a year. My diesels are also 8 years old and I am doing some scheduled maintenance on aftercoolers and heat exchangers which will be around $2000.
The maintinence on a new engine should only be changing fluids and filters for the first couple of years but then you should do some scheduled stuff which will be costly.
It seems like you would get the benefit of the diesel because of the increased range and economy but running that far on one engine would scare me unless I was in sight of land the entire trip, so the outboards would give me peace of mind.

Sorry for the long post, but the last thing to consider is how easily will you be abel to get maintenance done on the specific engine chosen. When I bought my diesel boat I only looked at specific engine packages because the service in my area for these engines was reliable.

Good Luck

tony

[61flathead]

Provie63

Most marinas carry "off road" Diesel which is not taxed. It should be dyed red.

[makosteve66]

Provie63 - 2/7/2008 8:51 PM

This is an interesting point..Where I fish in NJ, last season when gas at the docks was running between 3.10-3.20 per gallon, diesel was 2.60-2.80.. Yet at land based stations diesel was always higher than gas.. I'm not sure why, but someone told me it was due to "road tax".. anyone know if this is true?

Yes it is true - everywhere I see - on the water - diesel is cheaper than gas

[jrogers]

Thanks for all the quick and thoughtful responses. The manufacture website is www.seawolfmarine.com, and I am looking at the 30' model.

Based on our local costs at the moment, I have 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 to Whittier AK$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 today’s 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 (it is a fee tunnel through a mountian to get to the port from Anchorage).

Addressing the comments about distance from shore, we have a lot of protected water areas here. One is Prince William Sound, which is around 15,000 square miles of protected waters. If I choose to go to south east alaska, then I would have to make a couple of 100-200 mile runs that are exposed to the gulf, but that would be infrequent (a couple of times, if ever), and I would have the option of putting the boat and the truck on a ferry for this crossing if I desired. If I buy the boat in WA, I may decide to run up to Juneau with it, which is about 1000 miles, mostly well protected with communities every couple of hundred miles. In this case I would carry extra gas for the 8hp kicker, and go at hull speed if the motor died on me.


Jim

[SeaNile]

Diesel.

--JK

[jrogers]

Diesel vs. Gas Prices.

I have wondered about this price change as well. This is from the website http://www.eia.doe.gov/bookshelf/brochures/diesel/.

Until several years ago, the average price of diesel fuel was usually lower than the average price of gasoline. In some winters when the demand for distillate heating oil was high, the price of diesel fuel rose above the gasoline price. Since September 2004, the price of diesel fuel has been generally higher than the price of regular gasoline all year round for several reasons. Worldwide demand for diesel fuel and other distillate fuel oils has been increasing steadily, with strong demand in China, Europe, and the U.S., putting more pressure on the tight global refining capacity. In the U.S., the transition to low-sulfur diesel fuel has affected diesel fuel production and distribution costs. Also, the Federal excise tax on diesel fuel is 6 cents higher per gallon (24.4 cents per gallon) than the tax on gasoline.

[Drifter]

makosteve66 - 2/7/2008 9:07 PM

Yes it is true - everywhere I see - on the water - diesel is cheaper than gas

At least a portion of states will allow for an individual to apply for a highway tax rebate for gasoline used in boats.

[stapon251]

Automotive experience only. 5 gas boats. Lotsa cars. 1 you know what truck. Diesel if you use it. My guess is 300 hrs a year weekly use , diesel wins. Torque ++. Yay. Less use = headaches until resale.

[signmansez]

I ran and fished on a 33' Mirage with twin Volvo 260's and that boat was awesome. It burned about 2.5 mpg and could handle any kind of sea thrown at us. The boat cruised at 32 and was a dream to operate. The downside on the twin motor option was the tight quarters in the engine room. It was a tight, hot, knuckle busting experience to perform any kind of maintenance.
They offered this model in a twin outboard configuration but the diesel was the way to go. It was an outstanding package.

Go with twin diesels. You will get your money back at re-sale time.

[a7ewizard]

Other factors to consider...

Will the single diesel troll too fast for salmon/other species you may be targeting? Size your kicker accordingly and you probably will want remote controls for it.

Those VP diesels are heavy. Would a D4-300 be a better choice?

Would a 8.1 VP duo-prop perform well? The price difference plus interest saved will buy alot of fuel. The gasser will be cheaper and easier to service beyond routine maintenance. Lighter installation. Is range too compromised.

Diesel fuel issues if not properly treated and run alot.