FUEL EFFICIENCY - TWINS

H

hank schneider

New member
HELLO TO ALL
Still between boats - Andy has my CC 23 and I'm working on building up my treasure chest to get a 25. The Tomcat 255 has been suggested by several folks for the Carolina coast and also in the chop.
My question is would there be a major difference in mileage for the boat powered by a single 150 versus twin 150's at a comfortable cruising speed? This may sound like a dumb question but I towed the CC23 with a 6 cyl 4-Runner and then with a 8 cyl F 150. With no load there was a big difference in mileage but with the boat attached the mileage was just about the same. Any Ideas???
Thanks
Hank
 
Hank-

(If I understand your question correctly)

The single hulled 25 with a single motor will get better gas mileage than a cat with twin motors, overall.

The cat will be faster, but use more fuel, on plane and off, at displacement speeds.

It may be a matter of an average of, say (as a guess) 2.2 vs. 2.7 mpg (+/-30%, depending on conditions and piloting style), but the difference will be there.

The single hulled 25 would make a better displacement speed (trawler style) boat, where you could milk 5-6 mpg out of it, but shutting down one engine on a cat at displacement speeds could make it a close second choice.

The cat with twin engines will always cost more, both initially and operationally.

But if you want speed in moderate chop and waves with comfort, it will ride over them nicely.

Bob (Thataway) has owned both, and can give you more precise figures.

You'll need a larger tow vehicle with the cat, too (!)

But the cat will be roomer, a bit more comfortable, etc.

Joe. :teeth :thup
 
Captains Cat":1hlmh62e said:
Hank, I've read your post about 5 times and still cannot figure out what the question is... :disgust

Charlie
Click to expand...

It's clear he's asking if mileage suffers if one chooses twins instead of a single outboard, Charlie.

My answer is that two C22 Cdorys, the Halcyon and the Rana Verde cruised from WA to Alaska and back. Twice! Mostly within sight of each other the whole way. The Halcyon had twin 40's, the Rana Verde a single Yamaha F75. Their mileage for each trip was essentially the same. I think Chris (Rana Verde) mentioned the difference was too close to worry about. You could probably ask either owner for the details.

Admittedly both boats are owned by conservative experienced cruisers, not ski boat/bass boat/hot boat drivers, so YMMV (Your mileage may vary.)

Don
 
Our boat is a 25 with a single 135 Honda. Our friends, Brent and Dixie, have a TomCat with twin 135s. When cruising together, our fuel use is generally pretty close. That was pretty surprising to me initially. At any given speed, his hull is more efficient. Although the boats appear similar, the differences are major. Cost and weight difference is significant, right off the bat. The TomCat is much bigger on the trailer (and about 1,000 pounds heavier); it sits above the tires, the CD-25 hull rests between the tires. The berth in the TomCat is much larger. For me, the downside of that is the pounding on the bridgedeck at anchor on the TC255. Twice the maintenance for motor servicing. I like the ride of our 25, and our cruising style is a bit slower. The CD-25 fits our style. Brent and Dixie like to fish and the TomCat fits their style. Both great boats, but more different than the outward appearance or cabin layout might suggest.

If you plan to use your F150 to tow, you could probably get by with the CD-25 weight. I think the TC255 would be a bit much.

Good luck with the search/decisions.

Best wishes,
Jim B.
 
Sorry Folks
Long winded question - let me simplify - Tomcat with one 150 versus same Tomcat with twin 150's - at a basic cruising speed (18 mph) would there be a big difference in gas mileage???
The analogy was to my 4 Runner and F150 - same gas mileage on trips to Florida when towing my boat - seems like it took a certain amount of energy to travel.
If the mileage was close the big Hp would be nice for crossing to the Bahamas or going offshore for grouper - even with the extra service repair costs.
Thanks
Hank
 
Jim and Don
Thanks for the info - that was what I was thinking - running flat out the twin would use 2x more fuel but at an equal cruising speed there might not be much difference.
My 150 lost 1.5 mpg towing my 4 runner lost 7.5 mpg towing the same boat - terminal mileage was about the same
H
 
First you cannot do the Tom Cat with a single 150. It is not set up properly for a single engine. If you want to run one of the two 150s which most boats are set up for it is marginal, if you can get on a plane at all. I cannot, but my props are a bit agressive. Also with the liquid tie bar (hydraulic steering you cannot put one engine up and the other down and have them run properly.

As several said, I have owned both the 25 and Tom Cat at the same time. The 25 will get slightly better fuel economy, overall, but is a much slower boat than the 255. My 25 with a 130 would cruise at 18 or so mph. The Tom cat cruises at 25 to 35 easily. In a chop of 2 feet (even over 1 foot) the Tom Cat is far superior. But if you get over 3.5 feet, then the C Dory 25 at a very slow speed, might be slightly better. I found when cruising with trawlers, I did much better in any chop to speed up and go ahead and anchor until they caught up.

The Tom Cat has a bit more room--head is slightly bigger and the bunk is much bigger. But figure that the Tom Cat on a Trailer is close to 10,000 lbs, vs the 7500 lbs for the 25. My figures were average of about 2.2 to 2.3 for the Tom Cat (90% of the time at 25 mph)--and the C Dory--80% at 18 and 20 % at displacement speeds as about 3. But on a plane, the Tom Cat was almost as good as the C Dory 25.

I sold the C Dory 25 and kept the Tom Cat.
 
hank schneider":2e359zuf said:
Long winded question - let me simplify - Tomcat with one 150 versus same Tomcat with twin 150's - at a basic cruising speed (18 mph) would there be a big difference in gas mileage???
Click to expand...

This has been discussed before and the consensus was that you can't plane a Tom Cat with one motor, and even if you could, it would overstress that motor. Bottom line is that if fuel economy is your primary concern, you are better off with a 25 and one motor. IMNSHO, anyway.

Warren
 
I have posted about my tests where I planed my Tomcat on a single engine but would never do it again unless it was an emergency - i.e. one engine died and someone aboard was having a heart attack or something. It will stress the steering system and lug the engine.

However - running off plane I very much like the fact that I have "one hell of a kicker" to muscle through current/sea/wind, etc. should one engine fail. For example - once I was diving at Graves Lighthouse in Boston. At the end of a dive the current and wind had reversed such that we were being blown toward the rocks. One of my engines would not start - no sweat - fired up the other engine and had plenty of power to back us away. (Turned out I was 'just' out of neutral on the shifter and did not notice it - I was focused on the rocks and not looking down at the position of my throttles). Once I realized of course I popped the shifter into neutral and she fired right up of course.
 
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