The old debate, twin engines versus one engine on a C-Dory

Jim Gibson

I know this will spark a lot of controversy, but I could not help passing this along as it confirms what I have long thought but had no hard facts. This month’s Powerboat Reports (March 2007) tests the performance of a single engine (225 hp) versus twin engines (115 hp) on an identical 23 foot center counsel. The two engines even had a 5 hp advantage. All the engines were 4 stroke.

They found (1) significantly higher noise levels with two engines, (2) worse fuel economy with two engines, (3) slower at WOT with two engines, (4) two engines always operated at higher RPMs for the same speed as one engine, (5) more weight with two engines, (6) more upfront costs with two engines, and (7) more ongoing maintenance costs with two engines. Bottom line, the single delivers better performance at a lower price.

I believe these findings would hold true for a 22 and 25 foot C-Dory, though I am sure that many of you will not agree with this. I know there is a big COOL factor with two engines that I cannot deny. Just realize that there is a price to pay for it.

Also I know that there is the redundancy safety argument of twins, especially offshore. However, with the increased reliability of todays’s 4 strokes, the appeal of twins as a backup has lessened to a great extent. Also, a kicker is an option with one engine.

Finally, I realize that those with counter rotating props may argue that there is a handling benefit of twins around the docks and maybe in rough water. I would argue that the C-Dory is relatively light and maneuverable without twins. In rough water slow down or use trim tabs for control.

In the end, folks get what engine configuration they prefer. But I thought there were a few facts to shed on this argument.

Alasgun · Guest

Amen.
Mike on Huda Thunkit

Blueback · Posted: Mon Mar 12, 2007 1:39 pm Post subject:

Jim,
Excellent points made and suspions fully confirmed.
Blue

mikeporterinmd · Posted: Mon Mar 12, 2007 3:11 pm Post subject:

An interesting test would be with a 90 + 15 hp trolling motor vs twin Honda 50s

The 90+15 weighs about 480.
Twin 50s (40s too) weigh 410.

Anyone with fuel flow meters and a single, no trolling motor, want to do a test with an extra
120lbs on the transom vs. not?

Mike

flapbreaker · Posted: Mon Mar 12, 2007 4:47 pm Post subject:

tom&shan · Joined: 21 Sep 2006 Posts: 316 Photos: Dakota

I have a 90 hp and a paddle. Not sure how fast I can go with the paddle.
Tom

B~C · Posted: Mon Mar 12, 2007 4:54 pm Post subject:

what's the weight on that paddle? there's no way you can justify any boat related expense...the bottom line is, get what ya want.

A main and a kicker does somewhat negate the weight and maintenance expense issue

Byrdman · Posted: Mon Mar 12, 2007 5:51 pm Post subject:

Tom... How many cans Beer

per hour does that paddle burn and how often do you change the oil???

Forgive me... but is not one main motor and a kicker ...two motors? Smile

Yep, toss of the coin... each time I get ready to rig a boat I go thru this...changing my mind sometimes... like the 18 Angler I now have.. Bought it with one OLD original 84 modle Johnson 2 stroke...and before I put it in the water, I added a "portable" 9 hp new Suzuki 4 stroke...and bingo I was correct... about 1/2 mile across a large area in Lake Martin, wind blowing the wrong way, no one else on the lake with it so cold..and getting dark... that old Johnson gave up the ghost...and I was really glad I had a kicker...or....second motor.

Then, a week later, after removing that "portable" new motor so no one woiuld still it.... as I was bringing it back down the steap concrete walkway...the hand truck helping me toat that "portable" new motor hit a rock, forcing a hard immediate much faster than me pivit to the right, slinging me...and my new "portable" motor to the ground...with me in a very stupid man move....making sure my new "portable" motor landed on me instead of the concrete. ... Crook

When I got enough air back in my body to cry... I did. Then got up, and once more, finished the trip with the portable motor. ....and a few weeks later, bought a non-portable 50 hp suzuki..... and sold that chest chrushing, ego killing ya aint as young as you use to be "....$&^%%$^&* portable kicker.

Back to one motor.

Now.. looking at powering a new hull...and back to twins....both NON-PORTABLE. Cold day in August in Alabama before Byrdman buys another, "portable" kicker.

Byrdman

mikeporterinmd · Posted: Mon Mar 12, 2007 6:19 pm Post subject:

JamesTXSD · Posted: Mon Mar 12, 2007 7:47 pm Post subject:

We have been delighted with our single. However (and there's always a "however"), I do like the look of twins on the back of these boats.

Also, Brent and I did have the chance to try out the "paddle" solution one evening. While anchored out, we rafted up for the evening... to converse, eat, and toast the day's events. During that time, the boats rotated through 360º, wrapping our anchor lines. We paddled the boats (sure could have just motored around, too... but we were just messin' around) back around before we unrafted for the night. Nice that the water was clear so we could see exactly what was happening with the rode. Surprisingly, it wasn't that tough to move the boats with the paddles... not that I'd want to do it any distance or against a wind or tide. Wink

Best wishes,
Jim B. (still on the road, wishing we were still on the water)

Not For Hire · Posted: Mon Mar 12, 2007 9:11 pm Post subject:

Jim I believe each point made in the article is correct. These are the same points that Les Lampman (most eloquently) made on this very board a couple of years ago. Okay maybe three or four years ago on the C-Dogs but that discussion is preserved on this board. Of all the points the most significant to me is the noise factor. I would like quieter than I get running twins. Less cost and less maintenance is good also. You can probafly add in greater durability, benefits of fuel injection (in some lines), more room for swim step, more room for downriggers, and several other advantages to the large single engine.

On the other hand -
I like the look of twins from inside the boat, they are lower and block less of my view astern yet I can still see them fine for making sternway. I troll a lot and all too often in fair sized waves, a single 40hp is a dandy trolling engine in those conditions, a kicker is a little underpowered when it's rough. Twins give some lateral stability. Twins, particularly with Permatrims or some other hydrofoil give you many of the benefits of trim tabs without having trim tabs. Twins can be run one engine at a time when just moseying along, (when inland or exploring shallows, etc.) particularly if you have an electrical set up so that either twin will charge the house battery as well as its dedicated start battery. I don't race anyone in my C-Dory so top end doesn;t matter. I think the safety factor is mostly mythical with twins on 24 inch centers. Like they say its gonna be the gas or your're gonna hit something that takes out both props or lower units.

In short I got twins this time around. Next time I might get a single just to try it out. Or better yet get the cat and not worry about it. But wait that new 28 has that spiffy inboard - oh boy.

My boat comes out of the barn in five weeks, I am getting a little giddy.

Regards to all,

Mark

PS Jim - always appreciated those rpm studies you did and never said so at the time, thanks.

Dora~Jean · Posted: Mon Mar 12, 2007 11:23 pm Post subject:

Jim,

As you know I have twins and really like them, always had singles before. Noise factor, hmmm, I don't find that a problem at least with my twin Yami 80's, but then again I haven't compared against another CD25 with a single.

I believe Chris (Rana Verde) did a calculation on the twin fuel consumption of one CD22 (El and Bill's?) and his CD22 on last year's Alaska trip, virtually the same. So bottom type and loading could be a definite factor on these measurements. I'd believe the twins use slightly more gas, but not significantly.

I've run into seaweed a few times in weather and was sure glad I still had one engine moving us along while the other was cleared by shutting it down and tilting it to let it just fall off -- without even getting out of the cabin! Sure, not much, but I can see where things could turn difficult in a short time.

Like you said, to each his own, either can justify the usage of twins or singles by simply emphasizing one aspect or another. Thanks for the info.

Doryman · Posted: Tue Mar 13, 2007 12:10 am Post subject:

Just to stir the pot a bit -- I am considering setting Lori Ann up with triples Surprised

Actually, not, more like 2.2 -- the 2 Yamaha 150s and a Yamaha 8 in between them for trolling. However, I am going to give myself one good season with the twins before seriously thinking about the 2.2 option. I am not sure whether I can steer the 8 with the autopilot and have it tilted up independently of the 150s so it is out of harm's way.

Warren

flagold · Posted: Tue Mar 13, 2007 12:47 am Post subject:

C-Dory boats are used in far to remote places and over to great a distance for anyone to be without the safety and reliability factor that total redundancy gives in all systems and can be called on in a moments notice should either of the engines fail to perform as they likely will, so the the wise mariner in the C-Dory environment should make the judicious choice of twin engines, or a single Mercury. Mr. Green

thataway · Posted: Tue Mar 13, 2007 12:54 am Post subject:

Thataway has the 2.01 engine option. We have the 3.5 hp dinghy engine bracket, which mounts on the railing, fitted so it will slip into the dive ladder bracket and push the boat at about 3 knots. (See Picture #76/99)
This is probably not strong enough for an 8 hp, but the concept might be expanded for a larger motor.. No auto pilot, but it will tiller steer the boat with the main engines up.