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Old 06-11-2023, 16:08   #1
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Can anyone estimate the prop size for a Frers 41 IOR era racer?

It has a folding Martec Eliptec Mk3 that we need to replace, the pivot pin fell out and we lost the blades. The original boat build paperwork from 1988 didn't specify the size installed. The boat weighs 16,000 pounds and the engine is a Yanmar 3HM35F. I know the prop shaft size is 1-1/8", but I don't know what the gear ratio is, so not sure of the rpm at the shaft. I'm guessing it was maybe a RH18D x 12P? This boat is a joy to sail, but I'm not ready to forgo a functioning propeller. Any help much appreciated...
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Old 06-11-2023, 16:28   #2
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Re: Can anyone estimate the prop size for a Frers 41 IOR era racer?

The Kiwi Prop feathering propeller has adjustable pitch 10"-15" for 16" diameter prop, just need to check if diameter is OK with shaft and bottom of boat.
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Old 06-11-2023, 17:23   #3
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Re: Can anyone estimate the prop size for a Frers 41 IOR era racer?

Just google the vicprop propellor calculator. Seemed to be right for our fin keeler
I suspect you will need to find out reduction ratio for gearbox. Should be a plate on gbox
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Old 06-11-2023, 20:06   #4
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Re: Can anyone estimate the prop size for a Frers 41 IOR era racer?

Without the actual prop shaft speed, nobody can even offer a bad guess. I would strongly suggest you deal with a local propeller shop instead of asking the internet for wild guesses. At least you can hold them accountable if they get it wrong.

A mechanic who has been hammering on props for 30 years knows more about them than you ever thought possible to know.
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Old 07-11-2023, 12:15   #5
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Re: Can anyone estimate the prop size for a Frers 41 IOR era racer?

You have a choice of 2 different gearbox ratios in ahead and only one gearbox model, KBW10E. 2.14:1 gives you a shaft speed of 1498 rpm and 2.83:1 gives you 1129rpm and both are at the continuous duty engine rating, 3200 rpm. My photo of the page from the manual won’t attach so you’ll have to take my word on the numbers.
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Old 07-11-2023, 17:55   #6
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Re: Can anyone estimate the prop size for a Frers 41 IOR era racer?

Quote:
Originally Posted by BrianInBoston View Post
It has a folding Martec Eliptec Mk3 that we need to replace, the pivot pin fell out and we lost the blades.
And I know exactly why this happened...
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