Cat with Outboards - Performance Under Power ?

[thinwater]

Originally Posted by videorov

I forget which boat I saw that on. It had jackplates, like the some bay
boats do for fishing in the skinny water.
Ive been looking at the Gemini but real crazy about that diesel they keep
using in it, but you have no other choice in their design.
Outboards are so easy to work on since you can take them right out.
That jackplate lift idea I saw at a show is nice too.

... chop if mounted on the transom. They can easily come out of the water.

I don't know about the Gemini diesels, but the drives certainly need to be mastered and maintained.

On the Stilettos they are mounted on the rear crossbeam, which places them several feet forward of the transom. Works very well, even in very bad conditions. Been there. Had one.

Outboards are noisy, don't charge batteries, are lighter, and get poor mileage (compared to diesel).

On the PDQs and Seawinds (and some others) they are in wells 6-12 feet forward. Very dependable in any conditions. Pulling them for work is a bit pesty, but doable (see post).
Sail Delmarva: Removing and Replacing the Engines in a PDQ 32.

However, as you pointed out, I promise it's easier than doing an in-hull replacement or rebuild of an inboard.

[44'cruisingcat]

My Honda BF 20 "powerthrust" motors push my Oram 44C at a little over 10kts full throttle, cruise at 8 - 8.5 at more comfortable revs (4200-4500) using 2 litres per hour per engine.

Another 44C equipped with 21hp Nanni diesels with shaft drives performs very similarly, but with slightly reduced top speed, and uses just a fraction less fuel.

I have the advantage that I sail better - lighter and with no props and shafts dragging in the water.

[Therapy]

Originally Posted by delmitch

, but they had a rough night last night of 17.5m seas out on the Grand Banks! Not a record for us, the worst was 23m a few years back!



Mark.

In a Gem?

[sea-bee]

Originally Posted by 44'cruisingcat

In "Powerthrust" version they come fitted with a Honda 10 x 7 5/8 prop, with zero blade cup for better reverse thrust.

The biggest prop on the Honda is 10in diameter, and the Yamaha 12in.

The area swept by the 12in prop is 44% bigger than the 10in sweep, and this is disregarding the lost area in the center for the exhaust.

More horsepower on a little prop is like putting a V8 on your pushbike - you need better traction.

[Rapanui]

Maldives 32 with Yamaha high thrust 9.9 4 stroke at 3 tonnes plus cruising load does 7kt on flat water. Cruising at 5-5.5 kts could cross English Channel 65nm on 6 gallon tank. Only motored distances in calm conditions as she sailed faster on all points if there was 5+ kts of wind but she would make decent 4-5 kts progress into 7-8 winds on the rare occasions we tried it.
If the cat is light weight, 2 off Yamaha 9.9 high thrust make a good powering option and they have so many plus points, reliability, good torque, cheap (I paid £1700 for my last 9.9, compare to replacing 2 Yanmars 3YM on the Athena at £10k each), pretty economical, you can take them home to service them, light 46kg and they last, just sold on my 1995 9.9 that had been stuck on the outside of my boat 7 months each year in English weather.
I would not consider an outboard if the cat is heavy or the outboard position is subject to a considerable pitching as it will cavitate and lose drive etc. And only consider high thrust swinging a big prop slowly.
Good luck

[44'cruisingcat]

Originally Posted by sea-bee

The biggest prop on the Honda is 10in diameter, and the Yamaha 12in.

The area swept by the 12in prop is 44% bigger than the 10in sweep, and this is disregarding the lost area in the center for the exhaust.

More horsepower on a little prop is like putting a V8 on your pushbike - you need better traction.

Yes, that's the theory, and I've heard it thousands of times. But the fact is, we motor very well - better than smaller/lighter boats with the Yam 9.9s.

One possible reason is that our props are much deeper in the water - the extra long shaft means our prop hub is about 450mm under water.

[double exposure]

My 40' sailing cat was designed to run with outboards. I put a pair of Evinrude E-Tec 115 w/the I Command helm computers on her. Max speed is 21 knots, fast cruising speed is 15-17 knots and we burn 12 GPH, slow cruising speed is 7 knots and the fuel burn rate is 2-2.5 gallons per hour. We almost always cruise at 7 knots but it's nice have the speed ability when I want it.

[deckofficer]

A cruising cat you can water ski behind, how about that!

[double exposure]

Originally Posted by double exposure

My 40' sailing cat was designed to run with outboards. I put a pair of Evinrude E-Tec 115 w/the I Command helm computers on her. Max speed is 21 knots, fast cruising speed is 15-17 knots and we burn 12 GPH, slow cruising speed is 7 knots and the fuel burn rate is 2-2.5 gallons per hour. We almost always cruise at 7 knots but it's nice have the speed ability when I want it.

She is a 4 stateroom/ 2 head cruising cat that tips the scales at 15000lb. The true planing hull also allows the speeds to be run for any length of time.

[ejlindahl]

44 Cruising cat, I have followed your posts on your beautiful vessel and your satisfaction with the outboards it is equipped with. Your post #71 of January 2009 had a link to the website for your engines. The web page still displayed today though I suppose it is of the 2009 models, not the most current offerings from Honda. My question is that the site also showed a 25 hp Honda, do you think this 25 hp would have the same performance characteristics as your 20s? I ask this as I am looking at taking over a partially completed home built 46' lightweight cat that may be conducive to using outboard auxiliaries. I think I would want a bit more power than what you have. Thank you for your opinions.

[44'cruisingcat]

AFAIK the extra long shaft Honda 20s aren't available in the USA. Don't know much about the Honda 25s, but Yamaha make a high thrust 25 which has very big props, and they have been used on an Oram 48C with good success.

[deckofficer]

double exposure,

I went to the Kit Cat web site and they don't have any high res pictures. Any chance you can post some of yours? It sounds like an interesting boat.

[double exposure]

Originally Posted by deckofficer

double exposure,

I went to the Kit Cat web site and they don't have any high res pictures. Any chance you can post some of yours? It sounds like an interesting boat.

The sailboat on that site is mine. I bought her from the designer of them & owner of the company. I believe that they only built 11 boats. He told me that because they used all aviation grade material ( stronger, lighter & more flexible), they simply cost to much to build them. I don't think they built any after '07 or '08. With the exception of the open cockpit day cat that is currently on Yachtworld, mine is the only sailcat, all the others did not take the sail package and were built as powercats.
I've posted some boat pics on my profile here, but i can't seem to get my pics up on this thread.

[deckofficer]

Originally Posted by double exposure

The sailboat on that site is mine. I bought her from the designer of them & owner of the company. I believe that they only built 11 boats. He told me that because they used all aviation grade material ( stronger, lighter & more flexible), they simply cost to much to build them. I don't think they built any after '07 or '08. With the exception of the open cockpit day cat that is currently on Yachtworld, mine is the only sailcat, all the others did not take the sail package and were built as powercats.
I've posted some boat pics on my profile here, but i can't seem to get my pics up on this thread.

Got some from the site. Nice safe, flat deck.

[deckofficer]

From what you posted to CF,