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Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

Engine HP?

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ppetracca
Navigator

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USA
163 Posts

Initially Posted - 10/29/2002 : 20:04:29

I purchased hull 4795... Has original 9.9 electric start Evinrude, runs great. Is this enough HP for coastal CA? It will more than work for local lakes, but worried it is not enough for tide/weather conditions off shore. Any input greatly appreciated.

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H20boy
1st Mate

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USA
31 Posts

Response Posted - 10/29/2002 : 21:42:52

Everthing I have heard is 10hp is the max you will need, anything more is a waste do to the fact that sailboats do not plane on the water, hence the speed will not increase with more horsepower. Rick

Rick Price
"79" 25 swing
Tacoma, Wa

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ppetracca
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USA
163 Posts

Response Posted - 10/29/2002 : 22:24:22

Thanks for the info. Just want to make sure (I am used to a swing keel '22) so I'm double checking everything. Thanks again.

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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 10/29/2002 : 22:45:43

Yes, Rick is correct, a 10hp is plenty for a C25. I have an 8hp on mine and it has gotten me through some pretty nasty stuff without batting an eye. Unless you plan on pulling waterskiers, a 9.9 is the most you will need.

Don Lucier, 'North Star'
Catalina

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oldsalt
Admiral

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USA
578 Posts

Response Posted - 10/30/2002 : 20:03:06

I've sailed my fin keeled Catalina 25 since she was new back in 1983 and have always had a 2 stroke 9.9 extra long shaft outboard.

It's always had adequate power for coastal and "near offshore" work.

A Catalina 25 can achieve hull speed with the 9.9 under almost any conditions.

I believe the greatest issue is the shaft length. The problem you will face is cavitation when the prop leaves the water in the rough stuff. It's unavoidable with an outboard.

After spending 19 years with my boat, my experience tells me that a 9.9 is totally adequate. Any more HP would be overkill, and would come with the penalty of a shorter shaft.

Anything less might come up a bit shy in coastal/offshore conditions.

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RichardG
Admiral

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USA
990 Posts

Response Posted - 10/30/2002 : 20:20:18

Patrick:

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote> enough HP for coastal CA? <hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

I have been using a 6 hp Suzuki there for five years on my C-25. A slip neighbor uses a 6 hp Evinrude on his C-25. While some may not agree, I feel 6 horses is sufficient. If it's at least a long shaft, you should feel secure you have plenty of power with the 9.9.

RichardG 81 C25 SR/FK "Sanity"

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Phredde
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125 Posts

Response Posted - 10/30/2002 : 21:16:38

I agree with the others 9.9 should be fine and any more would be a waste. Phredde has a Nissan 8 hp. Usual max tides at the SF Gate are around 3 knots. But...some days can be a little over 5, so that with a stiff breeze in your face can make for really slow going. But I'm pretty sure a bigger motor wouldn't help much with the max hull speed issue. My advice is if where you're going has currents, time your travels to work with them not against.

Happy Sailing -

Phredde
Catalina 25
San Francisco

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Dave Bristle
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Djibouti
10005 Posts

Response Posted - 10/30/2002 : 21:35:33

I agree with all of the above--except that I suspect 6hp is close to or below minimal for working against a serious wind in a big chop in a sound or on the ocean.

For motoring in snot, the key is prop depth. Between your bracket and your shaft length, you want the anticavitation plate at least 6" below waterline. With 9.9 hp, that'll take you through most anything, even if the prop lifts and screems once in a while. I've proven that in some big, short waves that would nearly catapult a passenger out of the cockpit.

Dave Bristle - 1985 C-25 #5032 SR-FK-Dinette-Honda "Passage" in SW CT

Edited by - dave bristle on 10/30/2002 21:36:15

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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 10/30/2002 : 21:46:13

Richard,

You and your neighbor's 6hp outboards are probably running within their designed optimal wide open throttle (WOT) range(a good thing), whereas the higher hp models are running a little below their designed optimal range.

My 8hp Mercury develops it's rated horsepower at closer to maximum rpm, but I never operate the engine at that rpm. My max hull speed is attained at somewhere between 65-75% of the engine's max rpm and if I rev the engine higher, then the boat tries to plane(bow lifts and the stern sits), the motor bogs down, and the boat slows. I had a Johnson 9.9hp on my last boat(which weighed less than my C25) and that boat reached hull speed a little over half throttle.

I probably need a different prop so my engine will operate at an rpm where my horsepower is being produced(like my 15 year old 2-stroke snowblower that has only two speeds. Off, and FULL Speed) instead of somewhere below it.

Don Lucier, 'North Star'
Catalina

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 10/31/2002 : 21:01:34

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>
You and your neighbor's 6hp outboards are probably running within their designed optimal wide open throttle (WOT) range(a good thing), whereas the higher hp models are running a little below their designed optimal range.
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>
I don't know about that... Max hp is achieved at close to the redline, which is not the place to be running an engine for very long. The better indication of an engine's sweet spot is the max torque rpm level, which is lower on a 2-stroke and lower than that on a 4-stroke. If you're cruising at above that, you're burning more fuel than you need to and stressing the engine. My Honda 8 pushes us at 5 knots at barely half throttle. I haven't tried to reach hull speed (about 6.3), but if I did, I'd be wasting gas and making more noise. (Yes, Hondas can make noise if you push them.)

You might be right about the prop, Don, but you want to be at the torque peak, not the hp peak. The lower-pitched prop generates better thrust, forward or reverse. The standard-pitched prop tends to blow some water off perpendicularly to the shaft, which wastes power but doesn't help you go anywhere. (At the extreme, imagine a paddle wheel (infinite pitch) prop--it wouldn't drive you at all.)

Dave Bristle - 1985 C-25 #5032 SR-FK-Dinette-Honda "Passage" in SW CT

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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 11/01/2002 : 00:01:57

"...Max hp is achieved at close to the redline, which is not the place to be running an engine for very long..." - Dave Bristle

Dave,

I don't know about that. Take for example your 8hp Honda 4 stroke outboard. It has a full throttle(or WOT) rating of 4,500-5,500 rpm with the rated 8hp being developed at 5,000rpm. This full throttle range is the "sweet spot" that the engine was designed to operate up to and within. If your prop/hull combination only allows the outboard to rev to only 3,000 rpm's at wide open throttle(WOT) before bogging down, then your engine is being stressed by not being allowed to get to it's WOT range and, if ever needed, it's rated horsepower. Conversely, if your prop/hull configuration allows your outboard to rev over 5,500 rpm's at full throttle, then you need to change to a prop that will drop the motor's maximum rpm's to within the designed range.

According to WestMarine on prop selection;

"The basic rule is to select a prop which allows the engine to reach its optimal wide open throttle (WOT) rpm range, which is generally usually between 5000 and 5500 rpm, depending on engine type."

From the Michigan Propeller website,

"Now, determine your wide open throttle (WOT) RPM
For safety and efficient performance, it is critical that your engine operates within the RPM range recommended by the manufacturer. Matching the right prop for the load is the most significant factor of RPM adjustment."

Yes, when you are just cruising at 5 knots at half throttle you are probably saving gas and everything, but if a blow suddenly kicked up with wind and waves, you want to be sure that your motor can use all of it's 8hp rating(5,000 rpm) to move the boat. Imagine if you had a 15hp motor on the stern, but due to the prop/hull configuration, you could only rev it to an rpm that produced 5hp. Now that wouldn't be good!

As for a 2-stroke not liking to operate at high rpm's, I beg to differ again. Under load, 2-stroke chainsaws, weedwackers, and my trusty snowblower all like, and need, the high end of the rpm spectrum to do their work.

Don Lucier, 'North Star'
Catalina

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Mike Vaccaro
1st Mate

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77 Posts

Response Posted - 11/01/2002 : 08:20:52

Have found six horsepower to be more than adequate in the Gulf of Mexico. We have also added a "high thrust" prop, i.e., one of large diameter and low pitch, designed to allow the motor to "rev" at low speed. If you actually do the math for our boats, you'll find that around 8 horsepower is what is required. Our 2000 Johnson 6 is the same engine as an 8 turning at lower RPM. Whether or not any engine produces rated power or not is largely a function of having the proper prop installed for the application (i.e., is the prop moving through the water at 20 knots or 6?). We bought a six simply because the price was too good to pass up for a brand new, long-shaft motor!

Cheers,

Mike Vaccaro on the "Swoose"
84TR/SK #4707

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RichardG
Admiral

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USA
990 Posts

Response Posted - 11/01/2002 : 13:58:44

I'm not sure about all this tech stuff, but I generally run my Suzuki on one of two settings -- "on" or "off". For the last year, "on" is about 80 - 90% throttle and gives me about 5.4 knots (with no sail assist), less if dead into the wind/waves and/or with heavier loads. I used to run 100% all the time until I tested it under varying conditions and concluded it only produced an extra 0.15 knot speed. I understand that the previous owner also almost never ran the engine less than 100%, so for at least 12 years of it's 18 year life, the engine has been run long and hard and still seems to run fine (knock on wood).

RichardG 81 C25 SR/FK "Sanity"

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 11/01/2002 : 23:08:30

Don: I bow to West Marine (maybe) and Michigan Wheel (more likely)... But I didn't mean to imply that 2-strokes liked lower RPMs than 4-strokes--I think I said the reverse. Indeed, the lower pitch props of the "high thrust" outboards like mine are designed to let the engine run at more efficient RPMs at slow hull speeds. A standard pitch prop doesn't keep an engine like ours from overreving--it just loses efficiency when the boat is moving slowly and the prop spinning at high RPMs. I know that by comparing the response of our old standard-pitch Honda 8 and our new high-thrust Honda 8. Both would rev up as high as you could stand to hear, but the high-thrust (low pitch) prop bites much more effectively to start and stop a heavy, slow hull. When docking, the higher I revved the old one past a certain point, the less it did.

Dave Bristle - 1985 C-25 #5032 SR-FK-Dinette-Honda "Passage" in SW CT

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H20boy
1st Mate

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USA
31 Posts

Response Posted - 11/02/2002 : 15:14:46

I have a 9.9 hp long shaft on my boat...she does great even in the haevy tide rips through the Tacoma Narrows...when its roaring I will draw the swing up for less drag and cruise right through...Life is good.

Rick Price
"79" 25 swing
Tacoma, Wa

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