I am thinking about purchasing an Autoprop for my 1998 Catalina 36mkII. Currently my boat speed is between 6 and 6.5 knots at 2800RPM. I am wondering if anyone has any experience with the Autoprop, or has some first hand knowlege about the increase in boat speed using this prop. It's fairly expensive, and I'm trying to make sure there will be some positive change.
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Tom
I have it...I like it alot..it should definetly
increase your speed vs rpm's. Look back in the archives ...there has been alot of discussion on the Autoprop..Though I wonder why you only get 6.5 knots at that RPM...I think something is wrong (Tach?)...I have a 1999 36MKII with the Universal M35B (35hp) and I could reach hull speed (7.3 knots) with both my fixed 3 blade and of course the Autoprop. With the Autoprop I can achieve hull speed at less rpm that before...also it is great for motorsailing...even at lower rpm's the autoprop self pitches and really adds to the speed of the boat ...plus I beleive I am getting better fuel economy (not enough to pay for the Autoprop, but it does keep the fillups a little less frequent)
increase your speed vs rpm's. Look back in the archives ...there has been alot of discussion on the Autoprop..Though I wonder why you only get 6.5 knots at that RPM...I think something is wrong (Tach?)...I have a 1999 36MKII with the Universal M35B (35hp) and I could reach hull speed (7.3 knots) with both my fixed 3 blade and of course the Autoprop. With the Autoprop I can achieve hull speed at less rpm that before...also it is great for motorsailing...even at lower rpm's the autoprop self pitches and really adds to the speed of the boat ...plus I beleive I am getting better fuel economy (not enough to pay for the Autoprop, but it does keep the fillups a little less frequent)
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Ernie April
I agree with everything Tom said - and more.
Autoprop will stop your boat quicker than anything else short of grounding. Autopitcing reduces engine laboring when powering into a deep chop. Fully flipped blades significantly reduces prop-walk when backing. While it will give you up to a knot more speed in the mid RPM range, it will not increase top speed. Hull speed is, after all, hull speed. Bottom line is that Autoprop has been one of my best upgrades and saving fuel as well - for me maybe about 15% less for my C-42. While fuel economy probably won't pay for itself in savings, it will certainly pay the price differential between its competitors. Don't think you can go wrong. Ernie April Ernie April
Autoprop will stop your boat quicker than anything else short of grounding. Autopitcing reduces engine laboring when powering into a deep chop. Fully flipped blades significantly reduces prop-walk when backing. While it will give you up to a knot more speed in the mid RPM range, it will not increase top speed. Hull speed is, after all, hull speed. Bottom line is that Autoprop has been one of my best upgrades and saving fuel as well - for me maybe about 15% less for my C-42. While fuel economy probably won't pay for itself in savings, it will certainly pay the price differential between its competitors. Don't think you can go wrong. Ernie April Ernie April
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Sean
Autoprop - Just put it on
We just, last weekend, put the autoprop on the c-36 we race. It has definitely stopped the reverse walk. Note quite sure it slows/stops the boat as quick as fixed prop. We installed on a 1990. Our hull speed is ?slower? We are pending a test next weekend. Currently we are getting 5.7-5.8 (GPS) at 2200. We are curious to know what speeds others are getting and at what rpm range?
We just, last weekend, put the autoprop on the c-36 we race. It has definitely stopped the reverse walk. Note quite sure it slows/stops the boat as quick as fixed prop. We installed on a 1990. Our hull speed is ?slower? We are pending a test next weekend. Currently we are getting 5.7-5.8 (GPS) at 2200. We are curious to know what speeds others are getting and at what rpm range?
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Ernie April
Data: Fixed vs Autoprop on C-42
Here's the data. Model: Catalina 42 Mk II, wing keel. Engine: Yamaha 4JH (52 HP) Conditions: Calm, no current, average pair of opposite runs. Log: Autohelm knotmeter, just cleaned, same calibration. RPM FIXED AUTOPROP 800 1.4 kts 2.5 kts 1000 2.4 3.3 1200 3.0 4.1 1400 3.6 4.8 1600 4.1 5.4 My new motorsailing RPM -quiet 1800 4.6 5.8 2000 5.1 6.2 2200 5.5 6.5 2400 5.9 6.7 2600 6.2 6.9 My new (Autoprop) cruising RPM 2800 6.5 7.0 3000 6.7 7.1 3200 6.9 7.2 My old (fixed prop) cruising RPM 3400 7.1 7.3 My "got-to-get-there" RPM 3600 7.3 7.4 3800 7.5 7.5 When plotted, the difference in the curves is striking. Note that the boat moves substantially (~2X) faster at lowest RPSs. At first this bothered me a bit when docking. However, I found the higher speed made the helm more responsive and my docking actually got better. Moltorsailing RPM (1600-1800) is actually rather quiet. My Autoprop cruising RPM is relatively quiet at 2800 RPM, unlike the racket the engine makes at 3200 RPM. However, when I have to get somewhere, because the blades autopitch and won't stress the engine, I don't at all mind pushing at 3400-3500 RPM all day long, days on end. Unlike a fixed blade, Autoprop reacts to conditions and saves a lot of wear and tear on the engine. Note to Sean- When stopping or backing, goose the throttle initially, then ease it back when you see the results. It's very different from a fixed blade prop. If you dont ease back, you'll find yourself overshooting in reverse - it's very powerful, so much so that you have to pay close attention to the helm least it get away from you. It's the best... Ernie April
Here's the data. Model: Catalina 42 Mk II, wing keel. Engine: Yamaha 4JH (52 HP) Conditions: Calm, no current, average pair of opposite runs. Log: Autohelm knotmeter, just cleaned, same calibration. RPM FIXED AUTOPROP 800 1.4 kts 2.5 kts 1000 2.4 3.3 1200 3.0 4.1 1400 3.6 4.8 1600 4.1 5.4 My new motorsailing RPM -quiet 1800 4.6 5.8 2000 5.1 6.2 2200 5.5 6.5 2400 5.9 6.7 2600 6.2 6.9 My new (Autoprop) cruising RPM 2800 6.5 7.0 3000 6.7 7.1 3200 6.9 7.2 My old (fixed prop) cruising RPM 3400 7.1 7.3 My "got-to-get-there" RPM 3600 7.3 7.4 3800 7.5 7.5 When plotted, the difference in the curves is striking. Note that the boat moves substantially (~2X) faster at lowest RPSs. At first this bothered me a bit when docking. However, I found the higher speed made the helm more responsive and my docking actually got better. Moltorsailing RPM (1600-1800) is actually rather quiet. My Autoprop cruising RPM is relatively quiet at 2800 RPM, unlike the racket the engine makes at 3200 RPM. However, when I have to get somewhere, because the blades autopitch and won't stress the engine, I don't at all mind pushing at 3400-3500 RPM all day long, days on end. Unlike a fixed blade, Autoprop reacts to conditions and saves a lot of wear and tear on the engine. Note to Sean- When stopping or backing, goose the throttle initially, then ease it back when you see the results. It's very different from a fixed blade prop. If you dont ease back, you'll find yourself overshooting in reverse - it's very powerful, so much so that you have to pay close attention to the helm least it get away from you. It's the best... Ernie April
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Trevor
What about under sail?
I have a C36 with a fixed 3 blade and frankly am happy with the performance under power. However, I am considering an Autoprop or Max (ever heard of the J prop?) to improve sailing speed. My engine is the older M25 (21 hp) which is adequate for my power needs with the fixed prop... perhaps the Autoprop is a good compromise, since I understand the Max is less efficient under power but better under sail. Trevor S/V Dunoon, #640
I have a C36 with a fixed 3 blade and frankly am happy with the performance under power. However, I am considering an Autoprop or Max (ever heard of the J prop?) to improve sailing speed. My engine is the older M25 (21 hp) which is adequate for my power needs with the fixed prop... perhaps the Autoprop is a good compromise, since I understand the Max is less efficient under power but better under sail. Trevor S/V Dunoon, #640
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Ernie April
Autoprop well-behaved under sail
Trevor- It's amazing how my wake smoothed out after installing the Autoprop. Some years back Practical Sailor (if I remember correctly) published pictures of wakes produced by props towed beneath a boggey board. Autoprop's lack of wake was impressive. I don't have the data, but the absence of a churning wake at the swim platform must be equivalent to at least 1/2 knot. A three-blade prob is like towing a small drogue. Did you ever have your tranny lock up because you left it in forward and couldn't get it back into neutral to start the engine? Considerable force there which is slowing the boat. The autoprop will catch the slip stream if left in neutral and begin to turn with an slight increase in wake. With the tranny in fwd, the blades feather and the wake smooths out. There is so little pressure that it won't lock up the shaft. You can even start the engine with it in forward without stressing the engine - do it all the time. The saying is that everything about a sailboat is a compromise. Autorprop appears to be the exception - the darn thing is nearly magical. Ernie
Trevor- It's amazing how my wake smoothed out after installing the Autoprop. Some years back Practical Sailor (if I remember correctly) published pictures of wakes produced by props towed beneath a boggey board. Autoprop's lack of wake was impressive. I don't have the data, but the absence of a churning wake at the swim platform must be equivalent to at least 1/2 knot. A three-blade prob is like towing a small drogue. Did you ever have your tranny lock up because you left it in forward and couldn't get it back into neutral to start the engine? Considerable force there which is slowing the boat. The autoprop will catch the slip stream if left in neutral and begin to turn with an slight increase in wake. With the tranny in fwd, the blades feather and the wake smooths out. There is so little pressure that it won't lock up the shaft. You can even start the engine with it in forward without stressing the engine - do it all the time. The saying is that everything about a sailboat is a compromise. Autorprop appears to be the exception - the darn thing is nearly magical. Ernie
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Craig
Installation
Tom I also have a 36 MKII, did the prop fit without any alterations, i.e. was there enough clearance without installing a shaft saver or something?
Tom I also have a 36 MKII, did the prop fit without any alterations, i.e. was there enough clearance without installing a shaft saver or something?
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Tom Soko
Another Opinion
I installed an AutoProp this past spring, and I have been very pleased with the performance, BUT it vibrates more than my old 2 blade used to. I'm not positive, but I believe it's due to the fact that the tip-to-hull clearance was so small (<10%). If they made a 14" Autoprop, it could be a perfect prop for the C36.
I installed an AutoProp this past spring, and I have been very pleased with the performance, BUT it vibrates more than my old 2 blade used to. I'm not positive, but I believe it's due to the fact that the tip-to-hull clearance was so small (<10%). If they made a 14" Autoprop, it could be a perfect prop for the C36.
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Hayden Watson
one more point
I just wanted to add that forward is the correct gear with the Autoprop. The transmission manual says to use reverse. However, the shape of the Autoprop makes it freewheel in the opposite direction that a fixed prop would when the blades are feathered. This is just another of the benefits of the Autoprop. When sailing I always shut down and restart in forward. (Just one less thing to remember.) Hayden Watson S/V Papillon 1988 C30 tr/bs Spokane, WA
I just wanted to add that forward is the correct gear with the Autoprop. The transmission manual says to use reverse. However, the shape of the Autoprop makes it freewheel in the opposite direction that a fixed prop would when the blades are feathered. This is just another of the benefits of the Autoprop. When sailing I always shut down and restart in forward. (Just one less thing to remember.) Hayden Watson S/V Papillon 1988 C30 tr/bs Spokane, WA
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Sean
RE:Installation
The installation when smooth. Hardest Part - Pulling the old prop. Need a good prop puller. We actually installed ours with the boat in the water. Very easy. No alterations. Everything went as planned. Read the instructions they are right! (Everything went well till I dropped the key in the sand) But total change time was under one hour underwater. When we first put it on we noticed more vibration than with the three blade prop. We still have not had the chance to test the speed vs rpms (thanks for the info) will re-post when we know more. BTW forward is best.
The installation when smooth. Hardest Part - Pulling the old prop. Need a good prop puller. We actually installed ours with the boat in the water. Very easy. No alterations. Everything went as planned. Read the instructions they are right! (Everything went well till I dropped the key in the sand) But total change time was under one hour underwater. When we first put it on we noticed more vibration than with the three blade prop. We still have not had the chance to test the speed vs rpms (thanks for the info) will re-post when we know more. BTW forward is best.
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