As I have read from some owners, my Cat 30 will not respond with my current 2 blade prop. I would like to change it to a three bladebut don't want to ruin the little power plant
Will my Atomic 4 drive a 3 blde prop?
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I have a 3 blade with atomic 4 I bought from indigo online. It is made for the Catalina 30 and I am very happy with it. Reduced prop walk in reverse, but you have to get on it. In forward, gets to hull speed in a jiffy around 2k rpm's
The number of blades is irrelevant (within reason), to what that engine can turn, the primary concerns are pitch and diameter. Other factors are blade chord and profile, airfoil profile, etc.. The goal is to achieve the greatest speed possible at full throttle, and with the engine reaching max rated rpm.
Maine Sail had a good article on propeller selection, and he chose a good manufacture. If you can determine the correct prop you might be able to find a used one?
Maine Sail had a good article on propeller selection, and he chose a good manufacture. If you can determine the correct prop you might be able to find a used one?
Sometimes I feel like I'm the only sailor who has to stick up for our Catalina's to state that this boat after all is designed to be a SAIL boat, & not to be a powerboat. While everyone wants to get decent performance & power response from our AUXILLARY engine, the primary reason for buying a sailboat is the pleasure of sailing it. I know of no descently performing sailboat that performs rather well as a powerboat as well. While you can install all the blades that you desire, it is a proven fact that whatever speed you gain under power is the same, if not more speed that you will loose via increased drag under sail. For me the highest priority is efficiency under sail, so I cannot give in to the modern demand and quest for more & more power. I seem to be the minority in this view these days, I know. But personally I can't wait to turn that damn noisy, smelly diesel off as soon as possible. Although I do here good reviews of the Campbell Sailor's prop, which offers improved performance under power with minimal drag.
Yeah, its a sailboat. But it has an engine, and with todays fuel prices and environmental concerns we should all strive to make the motor part of our boats as efficient as we can, within reason. While most get many times greater economy than a powerboat, 15+ mpg vs 1.5 to 3 MPG for a powerboat, were still only doing as good as a full size truck. Anything to gain a reasonable amount of economy for reasonable cost, should be greatly encouraged whenever possible.
LOL
nice lecture... too bad it doesn't touch on the OPs question... I switched to an indigo and couldn't be happier... I have zero problems motoring through swells, current and chop... and the severe prop walk in reverse is a distant memory.
Have fun
Sure it will. There is/was one made for the A4 on which the pitch and blade shape exactly match the motor's load characteristics. We have a 1959 Rhodes Swiftsure 32 in our shop and that has had one (probably from its beginning). It was damaged during Sandy and we're replacing it.
You might ask Ken at Moyer Marine in PA, the northeastern Universal rebuilder, about how to get one. He's a great guy with help much to offer.
You might ask Ken at Moyer Marine in PA, the northeastern Universal rebuilder, about how to get one. He's a great guy with help much to offer.
I agree that it is a SAIL boat and that is what I do with it, as I only use the Atomic 4 for departing and returning to the slip. When I try to manouver in gusty weather and get spun around and end up reversing into the bay because the prop won't react to regular manouvers, I get pretty frustrated.
Appreciate the advise. Thanks
Appreciate the advise. Thanks
Yes, great lecture, but an Atomic 4 is not a damn noisy, smelly diesel which you also seemed to miss was the heart of this original post.
As a diesel owner you would not know of the joys of motoring quietly and smoothly with your relatively stink free old Atomic 4 spinning your prop.
I also prefer actually sailing to motoring but sometimes the wind dies. The auxiliary engine is also part of the safety equipment on any sail boat as is an anchor.
The Indigo prop specifically designed for the Atomic 4 direct drive engine and mentioned by others in this thread has been discussed now and then on the Moyer forum. The reviews fall pretty evenly into two camps: some rave about the improvement, others don't notice much of a difference.
While it's true the winglet design is innovative and intriguing I believe the differences in opinion have a lot to do with what the owners are comparing it to. If their original prop was suitably sized in the first place the difference in the Indigo seems to be difficult to discern. If they were overpropped originally (typical) the difference seems to be dramatic. RPM's are higher, fuel consumption is better, engine is generally happier but a lot of this improvement would likely have been realized with any prop of suitable diameter and pitch.
That's why I asked back in post #4 what size prop we're starting with, that is, the subject of this thread. If it's in the vicinity of 12x6 or 12x7, I wouldn't expect a dramatic difference.
And Caleb speaks the truth. Two years ago I was testing my fresh water cooling conversion, the boat backed into the slip and the engine running. A neighbor walked by, noticed the sploosh of water coming out the exhaust and asked, "Is your engine running? Man, I can't even hear it!"
While it's true the winglet design is innovative and intriguing I believe the differences in opinion have a lot to do with what the owners are comparing it to. If their original prop was suitably sized in the first place the difference in the Indigo seems to be difficult to discern. If they were overpropped originally (typical) the difference seems to be dramatic. RPM's are higher, fuel consumption is better, engine is generally happier but a lot of this improvement would likely have been realized with any prop of suitable diameter and pitch.
That's why I asked back in post #4 what size prop we're starting with, that is, the subject of this thread. If it's in the vicinity of 12x6 or 12x7, I wouldn't expect a dramatic difference.
And Caleb speaks the truth. Two years ago I was testing my fresh water cooling conversion, the boat backed into the slip and the engine running. A neighbor walked by, noticed the sploosh of water coming out the exhaust and asked, "Is your engine running? Man, I can't even hear it!"
Neil, thats a pretty telling post. The article Maine Sail wrote speaks very clearly to the advantages of a good prop, versus a poor one. Most of these sailboats have way more engine than the boat can really use. But because the gas engines have no governor to control engine speed, they use the prop to govern it. And because these are displacement hulls rather than planing hulls, what the boat requires in calm waters with no wind is much different than what they require in rough seas with strong head winds. I think many of these were way over propped just to make sure the engine came no where near red line engine speed.
You can under prop a diesel without any real concern because the governor wont let it overspeed. I would prop the motor to achieve about 75% hull speed at 75% rated maximum rpm, and put a throttle stop on the carb to limit maximum engine speed to whatever the engines rated at. If that means the engine is only producing 5 hp at 75% of max engine speed, great, thats about as efficient as your going to get.
I also see these A4's have a fixed main jet? There is a kit available to install an adjustable main, which if adjusted properly could save even more fuel while making more power. I would install the adjustable main before selecting the prop however, as well as making sure the engine was up to snuff.
But please, lets not pick on diesels. They arent all that smelly or noisy if their tuned and propped right, and they are the most efficient engine.
You can under prop a diesel without any real concern because the governor wont let it overspeed. I would prop the motor to achieve about 75% hull speed at 75% rated maximum rpm, and put a throttle stop on the carb to limit maximum engine speed to whatever the engines rated at. If that means the engine is only producing 5 hp at 75% of max engine speed, great, thats about as efficient as your going to get.
I also see these A4's have a fixed main jet? There is a kit available to install an adjustable main, which if adjusted properly could save even more fuel while making more power. I would install the adjustable main before selecting the prop however, as well as making sure the engine was up to snuff.
But please, lets not pick on diesels. They arent all that smelly or noisy if their tuned and propped right, and they are the most efficient engine.
Good points, all.
My A-4 is happy at my normal powering RPM of 70% max. rating. I figure the boat was designed with the Atomic 4 in mind and by the time mine was built Catalina had most of 600 chances to refine the prop size if necessary so by then they should have had it pretty well dialed in. If I were in the market for a prop for reasons other than performance (such as damage) I'd consider the Indigo but under the current circumstances I'm not motivated to spend the money.
Regarding the adjustable main jet, it's quite an aftermarket refinement (Moyer) and I'm certain jetting development continues. Again, as it applies to me, I'm perfectly happy with the standard fixed jet. My spark plugs read fine when I change them so what would I hope to improve? The adjustable jet is a necessity for those who choose to add a PCV system. On the Moyer forum my negative opinion of the PCV system is by far in the minority.
With the adjustable jet care has to be taken not to lean out the mix too far, it tends to elevate engine temps and in the extreme can damage valves.
And for the record, I'm fine with diesels. Had one myself in my last boat, a Perkins 4-107. It was a sweet running engine but then again it was a Perkins so it had better be. It's true they are noisier than their gas counterparts but full engine space soundproofing manages it well. Smells are easily managed by keeping things clean. Mine didn't smell.
The only problem I have is with the 'diesel snob' owner who looks down his nose at me because I'm a gasser. Don't deny it, they're out there. I once had a 'big dawg' on this forum offer the starting procedure for an Atomic 4 that ended with, "You turn the key and BOOM." I took him to task the best I could asking what kind of cooking fuel he had on his safe diesel boat, propane?? It was. Gee, a bit hypocritical aren't we? No problem with propane, a fuel with vapors also heavier than air, roughly the same explosive potential as gasoline and stored under pressure yet you'd never own a gas powered boat because they explode? He went on to explain all the safety features propane installations have, solenoid valves, isolated lockers and fume sniffers. Oh I see, you take precautions to keep it safe? (Yes he did) So why then is it assumed I don't do the same with gasoline (safety measures)? It wasn't pretty. In fact, it earned me a rather rude private message exchange with [name withheld] that I was a problem. It wasn't nice that I'd challenged a forum big dawg.
If my boat came with a diesel, no problem but I feel the same about gas, no problem either. There's no denying gas is quieter and by quite a bit.
My A-4 is happy at my normal powering RPM of 70% max. rating. I figure the boat was designed with the Atomic 4 in mind and by the time mine was built Catalina had most of 600 chances to refine the prop size if necessary so by then they should have had it pretty well dialed in. If I were in the market for a prop for reasons other than performance (such as damage) I'd consider the Indigo but under the current circumstances I'm not motivated to spend the money.
Regarding the adjustable main jet, it's quite an aftermarket refinement (Moyer) and I'm certain jetting development continues. Again, as it applies to me, I'm perfectly happy with the standard fixed jet. My spark plugs read fine when I change them so what would I hope to improve? The adjustable jet is a necessity for those who choose to add a PCV system. On the Moyer forum my negative opinion of the PCV system is by far in the minority.
With the adjustable jet care has to be taken not to lean out the mix too far, it tends to elevate engine temps and in the extreme can damage valves.
And for the record, I'm fine with diesels. Had one myself in my last boat, a Perkins 4-107. It was a sweet running engine but then again it was a Perkins so it had better be. It's true they are noisier than their gas counterparts but full engine space soundproofing manages it well. Smells are easily managed by keeping things clean. Mine didn't smell.
The only problem I have is with the 'diesel snob' owner who looks down his nose at me because I'm a gasser. Don't deny it, they're out there. I once had a 'big dawg' on this forum offer the starting procedure for an Atomic 4 that ended with, "You turn the key and BOOM." I took him to task the best I could asking what kind of cooking fuel he had on his safe diesel boat, propane?? It was. Gee, a bit hypocritical aren't we? No problem with propane, a fuel with vapors also heavier than air, roughly the same explosive potential as gasoline and stored under pressure yet you'd never own a gas powered boat because they explode? He went on to explain all the safety features propane installations have, solenoid valves, isolated lockers and fume sniffers. Oh I see, you take precautions to keep it safe? (Yes he did) So why then is it assumed I don't do the same with gasoline (safety measures)? It wasn't pretty. In fact, it earned me a rather rude private message exchange with [name withheld] that I was a problem. It wasn't nice that I'd challenged a forum big dawg.
If my boat came with a diesel, no problem but I feel the same about gas, no problem either. There's no denying gas is quieter and by quite a bit.
Good points, except for the adjustable main jet. The fixed jet is generally a compromise and will almost always provide a richer fuel mixture than the engine really needs. Yes, if leaned too far it will run hot and could damage valves. But a couple minutes reading the tuning procedure should cement it into the mind. Its not rocket science. Up into the mid 60's all the small outboards and most industrial engines all had adjustable mains. Way way back, the old Fords and other antiques had mixture control right on the steering wheel. Heck, my Dads first motorcycles had timing advance on the handle bars. And almost all general aviation aircraft with piston engines have manual mix control, which is a real necessity as you continually change altitude.
All you do is put the engine under load at approx 75% power, and slowly turn the mixture in (lean), until it starts to lose power (stumble), then turn it back out a titch until it runs smooth. If you want to really technical, you can do like some of the airplane guys do and install a pyrometer in the exhaust, and tune the mixture to 50 degrees below peak exhaust temp. It turns out though, that just adjusting it the way I explained works out nearly the same. The result can be as much as a 30% of more improvement in fuel consumption. Plugs, while a pretty good indicator, dont always tell the whole story.
Diesels have an economical advantage at low throttle settings, and only because not being throttled, the fuel mixtures can exceed 70:1. But as the engines reach full power, the fuel economy differences between a diesel and gas engine become almost invisible. At that point the only advantages the diesel has is in longevity and the fuel being less prone to fire and explosion. Throttled back, no gas engine can come close to matching the efficiency of a diesel. Maxed out, there is really no difference except the noise and the other points noted.
All you do is put the engine under load at approx 75% power, and slowly turn the mixture in (lean), until it starts to lose power (stumble), then turn it back out a titch until it runs smooth. If you want to really technical, you can do like some of the airplane guys do and install a pyrometer in the exhaust, and tune the mixture to 50 degrees below peak exhaust temp. It turns out though, that just adjusting it the way I explained works out nearly the same. The result can be as much as a 30% of more improvement in fuel consumption. Plugs, while a pretty good indicator, dont always tell the whole story.
Diesels have an economical advantage at low throttle settings, and only because not being throttled, the fuel mixtures can exceed 70:1. But as the engines reach full power, the fuel economy differences between a diesel and gas engine become almost invisible. At that point the only advantages the diesel has is in longevity and the fuel being less prone to fire and explosion. Throttled back, no gas engine can come close to matching the efficiency of a diesel. Maxed out, there is really no difference except the noise and the other points noted.
The adjustable main jet is fine for those who want to tweak and tune but in my case I have a 36 year old engine that runs as smooth as a sewing machine. In 1967 Universal moved to the Zenith model 68 carb (also manufactured by Bendix) that dropped the adjustable in favor of the fixed main jet. Those Universal guys were a pretty sharp bunch so I'm not persuaded that all of a sudden I need to revert back to the older adjustable.
However, if I were having issues I'd consider it in a heartbeat.
However, if I were having issues I'd consider it in a heartbeat.
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