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Old 08-11-2006, 04:05   #1
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out board size for cats

im one of those people who cannot see any reason to have anything but an outboard for a catamaran as they are light easy to remove and repair and cheap to replace, now my question or rather dilemma is should i go for 2 9.9 hight thrust yammies or 2 20 hondas they apparently have the same weight so at the worst with the hondas i would burn a little more fuel, but against this i would be able to plane anywhere i wantted to go(ok small joke)
what do you guys think and more importantly why do you think it
sean
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Old 08-11-2006, 04:28   #2
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For a 37 footer the outboards are OK. with a larger boat generally I have seen inboard diesels. We have a 34 PDQ that we have twin High Thrust Yamaha 9.9"S and have been very pleased with the performance and reliabllity. My worst problem has been the tilt locks and the hassle of lifting/lowering the engine. The tilt locks MUST be lubed regularly (meaning ALOT). How close are you to finishing your cat project?
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Old 08-11-2006, 04:49   #3
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optimistically speaking after chrissy hopefully the plan was to be finished at the end of october but i have goofed off a litlle which will put us just over the year mark, i only wish i had the money toi have a go at this full time like catmando, i reckon i could crank one out in no time asit is all the stopping and starting which is annoying
sean
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Old 08-11-2006, 05:48   #4
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Since you have made the decision to go outboard, I will limit my comments to that area.

Go with the power. Maneuvering to a fuel dock in a current, having the oomph to move the boat in one when the other fails, and dozens of other events will make you happy to have the extra HP.

I assume the Honda is 4 stroke since, I think that is all they build. Four stroke is less hassle and reputably more reliable than 2 stroke, although I have owned many 2 stokes and none ever gave me a poblem.

All this assumes the larger engine doesn’t carry too much of a price penalty.

You may not find a large difference in fuel consumption. The smaller engines will be working twice as hard to move the boat at any given speed as the larger engines. Of course run full throttle the 20s will gobble up about twice as much as the 9.9s. Neither engine is going to be a gas guzzler, by most folks’ standards.

Despite the starting and stopping, I am impressed with your progress. Keep up the good work.

George
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Old 08-11-2006, 09:56   #5
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I have an outboard on my Catalac and have 19 years of experience with it.

I started with a petrol 30 hp. This was hopeless in bad weather, and cavitated like mad. It was a standard long shaft and woked fine in calm conditions, but was still a pain to use.

In 1993, I changed to a diesel outboard (still available from yanmar, but very expensive) I had an ultra long shaft and hydraulic lift. A great engine, and the attachment of wings onto the cavitation plate meant that cavitation is a very rare problem. I dont much like the power curve, and it only provides 10 amps, but it will push against bad weather, and only uses about 1 gallon/hour at 6 kts.

If I was re-engining the same boat today, I would fit an inboard engine and a sillette leg, similar to the prouts and thus have some decent power generation.
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Old 08-11-2006, 10:01   #6
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Talbot:

What horse power is your diesel outboard and how much does it weigh?

George
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Old 08-11-2006, 10:06   #7
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27 hp

heavy!!!!!!!!!!!!!!
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Old 08-11-2006, 13:57   #8
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MORE horse power!!!!!

Go with MORE horse power and a long leg!!!!!

hmmmm...... there's nothing as nice as twin diesels

Rick in Florida
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Old 08-11-2006, 15:47   #9
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Hi There
How about considering evinrude e-tec 40 to 70hp same weight as two 9.9 25amp charging and you don't have to mix the oil with the gas.
Mike
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Old 08-11-2006, 16:12   #10
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Hi Northercat, not doing any work on boat at moment, recovering from an op, nothin' too bad.

Mate ,give serious consideration as to whether the Rhondas have a high thrust prop like the Yammie 9-9. The yammie pulls up real fast in reverse and you may find the others dont work as well.

Like seaking says, those tilt locks were a bitch and almost are'nt up to job with the high thrust in reverse , keep em well lubed, but I think they addressed this problem with the latest models, I think.

John Gross from Fastback Cat fame had a contact for extending the 9-9 with an additional 300mm. We did this on the last cat and it worked a treat.Never had a cavitation problem again. I also have a brochure for another crowd in Brisbane who do it but I've had no experience with them.

Have fun

Dave
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Old 08-11-2006, 16:21   #11
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Northerncat, I was pretty much sold on the Honda's, they have several advantages. Twice the power for the same weight, power tilt, which cures the tilt lock issues neatly, and a longer leg.

But recently I have heard they are not being made in Japan anymore, and quality has suffered. I am a fair way from needing motors yet, so I'm hoping Honda will fix this in the meantime. (It doesn't seem like Honda to let a quality problem persist for long)

If you need your motors soon check to see if the Honda's you might be getting were actually made in Japan.
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Old 08-11-2006, 16:25   #12
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High thrust props, did I mention this before?
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Old 08-11-2006, 20:08   #13
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The BF20 is available in a "powerthrust" version which has high thrust props.
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Old 09-11-2006, 06:21   #14
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i know that bob oram reckons that having one motor and a bow thruster is a pretty goo combination, the 40hp etec would be pretty cool and they have a decent gear ratio(visions of a 40ft easy planing around cairns)
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Old 09-11-2006, 15:13   #15
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Not so sure

I am not so sure that the outboards are the best choice. We have meet to different boat owners, one a corsair 36 and the other a 45 custom.

Corsair: We saw first hand that in any kind of swell the outboard couldn't be used because the prop was being pulled in and out of the water. When they needed it they couldn't use.

45 Custom. 2 beautiful 27hp diesel yanmar ourboards in a boat that was designed for this setup. He to complained that under moderate seas and up the props woudl go air born and then plunge back in the water. In St martin last year we had to move the boats because of weather and the swells caused then problems and concerns as they couldn't motor off anchor and what tuned in a lee shore. They made it ok, but it was a danger.

So the thought here is that if you are going the outboard route thinking it may be less expensive, there are risks to this setup. And almost every cruiser we have met including ourselves has kicked the motors on more than they thought they would.

Lastly: the gasoline outboards means you are carrying more of that volitale fuel onboard........
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