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Old 06-12-2024, 07:56   #46
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Join Date: Sep 2020
Location: Seabrook, TX
Boat: Catalina 30
Posts: 650
Re: Unable to motor at proper speed

Clean prop makes a big difference:


I replaced the propeller on my Catalina 30 for the same reason. The prop that came with the boat was extremely under pitched (paddle boaters would pass me by...).

I installed a Campbell Sailer prop and result was night and day. My sailboat became a powerboat.

Caveat: AS LONG AS....the prop is clean. As soon as any barnacles attached themselves to the prop, its performance would go to hell.

My two cents.

cheers
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Old 06-12-2024, 09:40   #47
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Join Date: Apr 2012
Posts: 201
Re: Unable to motor at proper speed

I don’t think I would worry about it. 5kts is the standard for a sailboat. Sailing or motoring. ) As long as all your variables are working for you. Clean prop, clean hull, good running engine, no worries!
Another option would be to buy a fixed 3 blade prop specked out for your boat. Plus you will have a back when the variable pitch fails. Not a big fan of variable pitch. Splitting hairs for speed in a sail boat. )

Oh! one other thought. 20hp seems a bit small for a 34’ sailboat. I had a 18 hp in a 27’, 6000#. Currently I have a 30hp in a 36’ at 6.5kts, cruise at 5.5kts.

Good luck🍀
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Old 06-12-2024, 10:00   #48
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Join Date: Mar 2009
Location: Seattle, WA
Boat: Bavaria 49
Posts: 29
Re: Unable to motor at proper speed

I’m just going to throw this out as we had a problem for a while where our engine wasn’t powering us at speed anymore. We hired a diver to check the prop, had a guy come look at the engine, etc etc. then we decide to verify the speed with a navigation app on our iPhone. You can guess where this is going. Motoring in four different directions and adjusting for current, we discovered that the electronics and knotmeter had gotten out of calibration and everything was reading slower.

Sometimes a sanity check like that can help. Do you trust all the data from which you are basing your conclusions?
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Old 06-12-2024, 11:18   #49
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Join Date: Nov 2016
Location: Colorado/Miami
Boat: Beneteau 381
Posts: 113
Re: Unable to motor at proper speed

FWTIW…… I had a similar problem with a Yanmar 2GM in a 33’ Cherubini (displacement circa 7000 lbs). At higher rpm it felt a little bit bogged down too, kind of like a truck hitting a hill on a highway. Not huge power loss, just kind of “boggy”. I experienced about a 1.5-2 knot loss of speed at the top end compared to what I had had before.

After prop cleaning and removal(Nada), putting back on a smaller OEM alternator (which helped a littttttle bit) I was told to check the mixing elbow. It wasn’t old and looked fine from the outside but inside it was all messed up. Replaced that and normal RPM to speed ratio returned.
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Old 06-12-2024, 20:24   #50
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Join Date: Feb 2012
Location: Gabriola Is. BC
Boat: Newport 30, Sirius 21
Posts: 333
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Re: Unable to motor at proper speed

Can you add more pitch to your present prop, or is it at max pitch now?

Why not give 'er another inch and see if you're happy with the results?
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