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Discussion Starter #1
My boat is a 1982 Catalina 27. It has a universal 5411, 11 hp engine. Since I have had the boat I have never been able to reach hull speed under power. I recently pulled the boat out of the water for a bottom job and inspected the propeller. It is stamped with 12LH7, a 12x7 left hand prop. Reviewing the specs for the engine and transmission it appears I need a right hand propeller. And likely a larger diameter too.

I have attached a photo of the prop and transmission. Does anyone know why there would be a LH prop on this engine and transmission? Does anyone have any recommendation on a new prop?
 

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Hull speed is a variable. seems to me if you have the wrong prop fwd would be Rev!
 

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It's possible to connect the shift linkage in such a way as to 'reverse' the gear.. if someone did this and you were always technically in reverse when going forward that might explain the lack of boatspeed. (IIRC the gear ratios are different fwd vs rev)

EDIT.. from your pic it doesn't look like the shift linkage connection is reversed, so not sure what to think....
 

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From the picture, it is a left prop, so the LH is correct. If you put on the same pitch that is RH, ran the transmission in reverse by the control arm selector, you may get what you want.:)
 

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Thank you for the responses. When I put the gear lever in forward (by moving it forward) should the lever on the transmission move forward or backward?
 

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According to the Hurth manual(s), if the gear shift lever on the transmission is moved aft (with standard straight/non V drive installation of engine) that's putting the engine in forward gear. It's a natural arrangement that works with pushing the control lever forward, it actually 'pulls' on the shift cable, moving the gear lever aft to the "A"/fwd position.

Where this can get confusing is if the cockpit controls are mounted unconventionally (ie sideways in the cockpit, or with the assembly 'backwards' on the cockpit wall)

If the boat's currently going forward when you 'shift to forward' at the control arm then the shifter arrangement and the prop are matched for direction.. however if it so happens you're actually running in reverse (arm Position "B") most of the time then you are probably using a less-than-ideal (or other than expected) gear ratio as they do differ.

One manual here:

http://www.c34.org/manuals/ZF_Hurth_Repair_manual.pdf

Thank you for the responses. When I put the gear lever in forward (by moving it forward) should the lever on the transmission move forward or backward?
Simply put, the lever on the tranny should move backward/aft.
 

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The C27 with the 11hp is no ball of fire, and I wouldn't expect to reach hull speed either. Anything above 5 kts at 2/3 throttle would be good.

You have 7000 lbs, and 11hp. That's about half the hp per lb that is considered ideal.

I spent a merry hour learning docking techniques in one. The highlight was when I tried putting throttling up in reverse to stop in a slip, and the throttle lever came off in my hand. Nice work with a snubber avoiding so much as a scratch.
 

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What is the difference in ratio ,,for'rd/ reverse? Hurth runs good either way. If you spring for a maxi you solve all the problems.
 

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Discussion Starter #9
Faster - I will have to check to make sure that the cable is moving as the manual says. I believe it is, but will check. Thanks.

Capt Len - I agree. My problem is when I call a prop manufacturer and give specs, they say right hand prop. That is not what is on there and I want to make sure I'm buying the correct prop.

More investigation required.....
 

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What is the difference in ratio ,,for'rd/ reverse? Hurth runs good either way. If you spring for a maxi you solve all the problems.
Depends on models, but something like 1.8 vs 2.2 seemed typical
 

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Most shifters can be reversed. The arm that pushes/pulls the cable can be taken off and put on the other way.
I think you could check the difference in gear ratios by running the engine while securely tied to a dock. If you get higher rpm in one gear, that ones running a lower gear ratio. You can also check by counting the revolutions of the shaft. Turn the engine over by hand one revolution with the compression release on, have a helper see how far the shaft turns in each gear. If theres no difference, then it doesn't matter.

Are you getting max rpm in fwd gear? Max on that engine is 3000, cruise would be around 2800. If your not getting that, then your over propped as it is and putting a larger one on, right or left, will just make it worse.
If your running a lower ratio in forward, you should be getting to max rpm more easily. The slower the prop turns, the less resistance and the faster the engine will run.

The only reason RH is considered "standard" is so that the prop effect pulling the stern to one side or the other in reverse is the same on most boats. If yours is the only boat you run, once you're used to it, it doesn't matter. If running the trans in reverse all the time hasn't killed it by now, it's not going to.
 

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Discussion Starter #12
I don't have a tach so I'm not sure of the rpm's. It seems to me that if the propeller is the wrong rotation, I am pulling the boat through the water by "clawing". And not propelling the boat. (If the transmission is in the correct position). Would this be correct?
 

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I don't have a tach so I'm not sure of the rpm's. It seems to me that if the propeller is the wrong rotation, I am pulling the boat through the water by "clawing". And not propelling the boat. (If the transmission is in the correct position). Would this be correct?
Don't think so.... If the propellor is the wrong rotation the boat will be going the wrong/opposite way. However if you're running in 'reverse' to go forward then the prop blade is working in an inefficient backward direction (like it normally would when backing up)

When you put the boat in 'fwd' (as you're using it now) the prop shaft should be turning CCW if you're regarding it from astern. If that's true, then the LH prop is working as it should. Whether the gear is truly in 'forward' or not is another matter, but not a fatal one since hurth drives don't care which you use. The different ratios could have an effect on your ultimate speed (but so can so many other things.. cleanliness of prop and bottom most especially - though your photos show that things are OK there.)


When you can, try to confirm the arrangement of the control lever assembly and the gear arm position when going ahead... and the actual shaft rotation.
 

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That 2 bladed prop is has almost the same efficiency in both directions.
Could be.. I suppose that depends on the cross sectional shape.. ;)
 

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There is some camber to the blade on the forward side, and flatness on the rear side. But the proof is in the pudding. :) Seven inches of distance per revolution, goes both ways. Merry Christmas!
 

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I had a 5411 in my previous boat - a 30 ft Cal 9.2. It displaced 7000 lbs and did a pretty good job of moving the boat. I could get close to 6 knots wide open and cruise at 5 or so was very efficient (about 1/3 gallon an hour). It had a RH Martec folding prop and I believe it was about 12 inch diameter with a pitch of 10 or 11 inches. Not sure what the reverse reduction is - forward is 2:1. Here's a link to the manual if you don't have one.

http://www.catalina30.com/TechLib/Engines/M5411/M5411_Maint.pdf
 
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