370 / 375 - Folding Prop Size

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Folding Prop Size

Printed From: myHanse.com
Category: Hints & Tips
Forum Name: 370 / 375
Forum Description: 370 / 375 Hints, Tips and News
URL: https://www.myhanse.com/forum_posts.asp?TID=12004
Printed Date: 27 March 2026 at 03:40
Software Version: Web Wiz Forums 12.06 - https://www.webwizforums.com

Topic: Folding Prop Size

Posted By: H8jer
Subject: Folding Prop Size
Date Posted: 17 June 2020 at 07:41

Currently we have a Flex-O-Fold Racing folding prop 16x13L 2-blade. (Recommended by Flex-O-fold)

We have the 30hp Yanmar 3YM30C (Year 2008) and the (SD20) gear-ratio is 2.64:1. (3YM30C is max rpm 3600 but 3489 at continuous)

Our normal cruise speed is 6.2kn at 2500rpm (clean hull).

Some weekends ago we pulled a 37-feet sailboat in distress. During this action I was surprised that we only lost 1 kn pulling the boat.

This makes me wonder if the Prop size is a bit too small, as it looks like the engine has plenty of power.

I am a bit uncertain what our max rpm is, as the gear/throttle-control hits the starboard storage-locker/seat and I don't know if the "pedel is floored" at that position.

I will try and measure the real rpm with a Digital Laser Tachometer RPM Measurement.

Do anyone have else have a 17x13L 2-blade folding prop on their 30hp Hanse 370?

/H8jer

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Hanse 370#487 30HP 3-cabin

Replies:

Posted By: Matt1
Date Posted: 17 June 2020 at 08:07

Hi - Can't comment on the 370 but on my 418 I have just gone from an 18" (unknown pitch) 2 blade fixed prop that Hanse fitted at the factory to a flex-o-fold 3 blade 17"x14" - this is married to a 3JH5E 39hp SD60

I've only used the new prop once but it looks to have been transformational - taking my speed from a pitiful 4.9kn at 1900 rpm to 6.2kn at 1900 rpm

With the previous prop I could well exceed the engines max revs

I'm hoping to get out on Friday to do a complete comparison at different rev ranges and will post a summary on the 418 section of the forum

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Hanse 418 #64 EmBer. Hamble, UK

Posted By: Forth2
Date Posted: 17 June 2020 at 08:25

I have a Hanse 315 with 3ym20 sd20 and a 17x12 2 bladed flexoxold.

The recommendation from flexofold was 16x11. I increased both with 1 inch to get lower revs at cruising speed and more power for driving into strong headwinds.

This has been working fine now for 12 years.

The prop is quite heavy so I try to be slow in switching from forward to reverse. Dont want to break the sd20.

The recommendation from Yanmar for the sd20 max prop diameter is 16 inches.