We cut 500 pounds off the bottom of the iron keel. Cutting iron is difficult. We need less draft in NC. Installed a new 1GM10 that's fits well. Currently adjusting the 22 mm shaft for a RH prop. 22 mm and 7/8 inch is the same thing. Looking forward to some coastal sailing. We may need a permanent reef or some inside lead with the modified keel.
Yamaha 25 keel and engine
- Thread starter yamaha78
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What was the original draft and new draft? On a 25 foot boat, 500 pounds of cast iron is a substantial amount of keel area and ballast. You have not only affected the boat's stability but its pointing ability. Have you considered adding a bulb to the bottom of the remaining keel. Contact Mars Keels in Canada. You would probably have to add back the original weight plus 20% or more to regain the original stability. Mars Keels will be able to give you more specifics.
My modified keel
Thanks for your suggestions. The modified boat's balast to displacement ratio is 31% and the draft should be close to 4 feet. I think it is going to work as is and I will report the results of the first sail when it happens.
Thanks for your suggestions. The modified boat's balast to displacement ratio is 31% and the draft should be close to 4 feet. I think it is going to work as is and I will report the results of the first sail when it happens.
I did some poking around on the internet for specs on the Yamaha 25. The displacement is 3748, ballast is 1433, ballast to displacement ratio would be 38%. If you removed 500 pounds from the keel, the ballast would now be 933 and the ballast to displacement ratio will now be 25%. I'm sure you'll notice a big difference. The original draft was 5'-5" and you reduced it to 4'-0". Those changes are sure to yield substantial changes in the sailing characteristics of your modified boat. I'm not a naval architect but I would think you are going to have a very tender boat. I have to wonder what this has done to the limit of positive stability. Might be scary dangerous! 
http://www.yamahasailboats.org/Brochure page 3.jpg
http://www.yamahasailboats.org/Brochure page 3.jpg
The Yamaha 25 mkII is a great sailboat. I hope you haven’t created a worthless powerboat.
My question is, how does the new Yanmar 1GM10 with the vertical cylinder fit under the V-berth space that was designed for a horizontal cylinder YSM-8. My CAL has the bigger brother (horizontal cylinder) YSM-12 and I always wondered if a newer vertical Yanmar would fit.
My question is, how does the new Yanmar 1GM10 with the vertical cylinder fit under the V-berth space that was designed for a horizontal cylinder YSM-8. My CAL has the bigger brother (horizontal cylinder) YSM-12 and I always wondered if a newer vertical Yanmar would fit.
For accurate calculation purposes, you need to remove the 500 pounds from the total displacement. I have a plan "B" if the keel doesn't work well. The new engine is smaller in size. No problem with the engine's vertical fit under the V-berth. Lots of room around the outside of the engine. The prop shaft has to be recut for an American prop. It needs a RH prop and the shaft may become too short during the recut. I am currently having my shaft extended 12 inches.
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