Freedom 44H Engine big enough/too big?

Engines, Drive trains, Propellers, Steering, Ground Tackle and other mechanical system
rds
Posts: 50
Joined: Mon Jul 06, 2009 9:32 pm

Re: Freedom 44H Engine big enough/too big?

Post by rds »

These all tie together and it's fairly clear to me that Freedom didn't understand the mathematics behind optimal prop sizing.
Yes, I asked myself the same question. I got some old surveys / documentation with my boat and reading them concluded that 19’’ max- prop has been originally installed by the factory. According to the surveys my lugging yanmar always suffered from oversized prop, even with 2.64 gear ratio.
I also recall reading this article referred by Geoff in one of his posts , interestingly enough I noticed 2 kinds of vibrations in the shaft: one was kind of acute , constant after 1500 rpm, slightly increasing with rpms and the other one is king of “wobbly” after 2500 rpms which exactly coincided with 95 ft / sec blade tips speed of my orig. 19’’ prop. I can’t say for sure if that was cavitation .. but cutting prop to 17’’ diam. definetly helped
Don't know my shaft dia. but need to replace it anyway - what is the shaft dia. on your F44 c/b?
I also replaced the shaft / cutless bearing . I noticed that my shaft has been slightly worn on one side in area of contact with cutless bearing , probably from misbalance in max-prop. While checking around for the new shaft or repair my old shaft found again that price range is quite drastic .. from $400 to $1500 and seems to be not justified by any means.. eventually I found a place called ‘properpitch’ in Delaware. I do not have any affiliation with them. They seems to be quite knowledgeable and friendly , best price, prompt shipping . They have website , price list ..e.t.c. I can recommend them highly.
That is what I found out as well. Mostly there are two types alloys for prop shafts on the market: alloy 22 and alloy 19 . A22 is almost twice more expensive with marginally better material properties. Talking with these guys I understood that for my particular 1 ¼ ‘’ shaft it is just no matter if it A22 or A19 while all the other shops simply insisted on A22 only..

Freedom44
Posts: 8
Joined: Wed Oct 07, 2009 4:33 am

Re: Freedom 44H Engine big enough/too big?

Post by Freedom44 »

Hi
I am a bit late into the discussiuon, but the weather in the UK has been too fabulous to read blogs and not go sailing.
I replaced my Perkins 4108 2 years ago on my F44 with a Beta 50hp and a new gearbox. It drives a maxprop. I get a cruising 6kts at about 1800 rpm. Fuel consumption about 3litres per hour.. Wonderful engine based on a Kabuta block. Reasonably quiet with useful prop wash. I added a monster second alternator dedicated for the house batteries.
I regret not doing this long ago as I have been chucking good money after bad on the old engine.
Richard
Freedom 44 "Windwalker" located Plymouth UK

Matso
Posts: 7
Joined: Wed Apr 24, 2013 9:35 am

Re: Freedom 44H Engine big enough/too big?

Post by Matso »

Hi RIchard, thanks for your input!
Have been looking at the Beta 50 myself, good engine and company.
What gear ratio, size max-prop (2 or3 blade?) and pitch do you have?
Cheers,
Mats

Freedom44
Posts: 8
Joined: Wed Oct 07, 2009 4:33 am

Re: Freedom 44H Engine big enough/too big?

Post by Freedom44 »

Sorry for the delay : Been sailing! I have a F44 cat ketch which i bought in Maine in 1999. I presume this the same as a F44H but whatever, i dont think it will make much difference to my experience.
I replaced the perkins 4108 with a perkins 4107 in 2000 in USA which was a mistake. It was a very old fashioned engine based on pre war Bedford truck and therefore noisy but reliable.
In 2010 I bit the bullet and replaced it with a Beta 50hp which is based on a kabuto block. The transformation was incredible. I have a maxprop and at 1800 revs in flat conditions i achieve 6 knts using 3 litres per hour. I wished I had been braver and sorted it earlier.
I dont think a bigger engine would achieve that much, as at full blast, the stern digs in and you only go marginally faster.

Putting it in was interesting as it was all a bit further forward and required some alterations to the carpentry but quite acceptable.
My only regret is that we didnt choose the shallow sump option as this would have made the fitting a lot easier.
Richard Franklin
Freedom 44 "Windwalker" located Plymouth UK

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