Mercury I/O vs OB vs Diesel comparison

blubeast · 06-02-2003, 09:29 PM

For those thinking about repowering... the July issue of Popular Mechanics has a side by side comparison of three engines on the same boat hull. (a Trophy 21' - 85 gal fuel tank) Interesting reading and stats.

They must of heard Pilar at the last TA meeting. They place alot of emphasis on the mpg achieved. At cruising speed (20mph) the I/O had a projected range of 274 miles; the Optimax 261 miles, and the new Cummings/Merc diesel.... drum roll pls.... 515 miles.

John... is that enough to make it to Tuna Town & back?

Pilar · 06-02-2003, 09:45 PM

500 + miles???

Uh, yeah!

Blubeast, we typically run 150 miles on a TUNA! hunt. I can't even imagine a 500 mile trip!!

Having adequate fuel and good economy means you have one less thing to worry about .. running out of fuel or ending the hunt early because you are worried about fuel.

[ 06-02-2003, 10:46 PM: Message edited by: Pilar ]

skein · 06-02-2003, 09:59 PM

Wow! Hey Rod, you've been wanting a repower. Here's the school solution! 500 miles. Sheesh.

Wasn't there a song about that? "Five hundred miles, five hundred miles, ...." We can sing that around the old crab cooker. :grin:

You can bet I'm gonna read that article.

Skein

fish assassin · 06-03-2003, 06:28 AM

With the twin MerCruiser diesels on Pacific Mistress with 280 gallons of
fuel on board and using 6.5 gallons/hour I figure I can go about 800 miles
and still have about 20 gallons reserve in the tanks. Depending where the
fish are, I can fish 2 or 3 days for TUNA before
I fill up and the most fuel
I've ever had to take on was 160 gallons.

Have I told you how much I LOVE my diesels? I used to burn through 50-70 gallons
of premium grade gas PER DAY fishing the dory with a single 90hp Johnston outboard
on it!! I actually had to come in early off the tuna grounds a few times because
I was running short on fuel and I was carrying about 70 gallons with me!!

I DO love the efficiency of those diesels!! :grin: :grin: :grin:

-assAssin-

8knots · 06-03-2003, 07:31 AM

Wow, 6.5 gallons an hour. That is one efficent hull. What is your typical cruising speed? I hold 640 gallons on my boat, but she is a slow one with two 120 Ford Lehmans. It is made more for long range cruising than fishing. So, I'll fish while I cruise. It has been to AK from Portand twice with the prior owner and I took it up to Barkley Sound two summers ago. Gotta stay employed to keep it long enough to retire and spend 4 to 5 months up north in the summer and winters in Zihua.

Threemuch · 06-03-2003, 08:28 AM

8kts, nothing wrong with the slow boat. I have fished many times off my friends 42' Sea Chief which is a single 120 ford lehman. We always seem to get there just as the bite turns on. I spent 10 days on the blue on that boat. Great fun.

Those diesels are efficient, but you can buy a bunch of gas with the 10-15K you spend in upgrading from gas to diesel.

David Pascoe, a well published marine surveyor has some interesting writing on the subject on his website:

David Pascoe Gas V. Diesel part 1

You might be startled at some of his conclusions.

A great site on boats, if you don't mind some snobbery. He is pretty hard on boat manufacturers. Read some of his reviews to see what I mean.

skein · 06-03-2003, 09:08 AM

I agree that you can buy a lot of gas for 16K, but it's the immediate payoff in extended range that interests me. I had a Ford crewcab with a 460 that had an effective range of 250 miles. Now I have the same thing in a Powerstroke diesel with a comfortable range of 550 miles. Out in the desert (or the ocean) that's an important difference.

You can also make the "resale" point, but honestly, I don't buy a boat with the next owner in mind. I buy it for ME, and for what I can do with it right NOW.

Skein

corrirod · 06-03-2003, 09:20 AM

Hoboy, 500+ mile range could get me in alot of trouble! :grin:

That would turn the 45/125 line into the starting line instead of the turn around! :shocked: :shocked:

Hmmmmmmmmmm........ :tongue:

fish assassin · 06-03-2003, 09:28 AM

My typical cruise speed in "energy saving mode" is between 20 and 23 knots.
That is about 28-29 hundred RPM. Gotta love those catamaran hulls!

Total Horse Power is 500 for both engines. Top RPMs is 3800 with a 37.5 knot
top end!

-assAssin-

Quote:

Originally posted by 8knots:
Wow, 6.5 gallons an hour. That is one efficent hull. What is your typical cruising speed?

corrirod · 06-03-2003, 12:02 PM

MB, you can do 2 trips for the same cost as I can do one! :shocked: :grin:

Diesels aren't real good down in CA so perhaps you should sell it and get another gas boat? I guess I could take the diesel one off of your hands if I have to.

:tongue:

Master Baiter · 06-03-2003, 01:55 PM

Corrirod, I guess I may as well throw in the diesel rig also! :grin:

Miss B Haven · 06-03-2003, 02:04 PM

Rod- We can use Miss B for a Mother Ship (300 gallons) just float around and TUNA fish for a week straight. Lessee 25 per day x 7 days x 5 guys....... :shocked: :grin:

fishwhenican · 06-03-2003, 06:55 PM

I would have to disagree with David Pascoe on many different points, some of which seem to be directed at 30 year old technology. Design improvements in piston rings,combustion chambers,and injection systems have improved reliabilty, reduced smoke and improved power. Corrosion is a BIG factor to consider as well as engine/fuel system design. The manufactures make "mistakes" in design of marine, offroad and on highway engines, not just marine. Don't buy a marine engine that is the max hp of any in that engine series.

I'm not sure what category Mr. Pascoe would classify the Cummins 6B series. Automotive? Industrial? What is the difference between a tractor plowing 500 acres and a couple of TUNA! trips to an engine?

There now I've vented and feel better
:smile:

Master Baiter · 06-03-2003, 11:20 PM

Although diesel has a higher intial capital cost, the cost is usually held and recovered partially in resale value. I got a 70 gal tank and my range is 350 miles.

MB

diesel for life!

WaterDog · 06-04-2003, 05:13 AM

You can sure tell who loves the smell of diesel in the morning. :grin: Me included! Go Boating did a write up on the 21' trophy diesel a while back and I thought that would be a sweet ride. Since I already have a diesel truck, I would not hesitate to get a diesel powered boat. Well, provided I could afford it.

Master Baiter · 06-04-2003, 06:37 AM

What's up DOG! Good to hear you weigh in. Is that article on line somewhere? My buddy was thinking about trading in his OB trophy for the diesel.

Hey Fishwhenican, I have to agree with you about the Pascoe article. I did alot of research before I decided that diesel was the right choice and his biased views did not change my mind. A good boat diesel resource is boatdiesel.com for anyone interested. I too love the smell of diesel in the morning!]

MB

WaterDog · 06-04-2003, 07:33 AM

MB - You know when there is talk about diesel, I gotta chime in.

Here's the link to the Trophy Review.

Go BOATING Article