With the higher gear ratio you will likely want to increase the pitch on your prop to maintain the same load on your engine. This is what I wrote about changing the whole engine in my 40: https://www.cruisingworld.com/new-engine-for-an-old-boat/ Andy
Andrew Burton 26 Beacon Hill Newport, RI USA 02840 www.burtonsailing.com http://sites.google.com/site/andrewburtonyachtservices/ +401 965-5260 > On Jan 1, 2020, at 17:02, ALAN BERGEN via CnC-List <cnc-list@cnc-list.com> > wrote: > > Because of the higher gear ratio, you'll have to run the engine faster to get > the same boat speed as you do with your present transmission - theoretically > about twenty-two percent faster (2.61 divided by 2.14 times 100%). You'll be > using significantly more fuel, and you also may not be able to reach maximum > boat speed without exceeding maximum rated engine speed. > > Alan Bergen > 35 Mk III Thirsty > Rose City YC > Portland, OR > >> On Wed, Jan 1, 2020 at 1:44 PM Olivier Chatot via CnC-List >> <cnc-list@cnc-list.com> wrote: >> Hi all, >> >> I have an interesting situation with my transmission. I would like to share >> it with you and get some opinions. >> >> I have a Yanmar 3HM35F engine with a Kanzaki KBW10 transmission. I need to >> replace this transmission because it's been malfunctioning. >> >> Someone near me has a new Kanzaki KM3P for sale. I believe the mounting >> flange is the same shape and size, so physically mounting this transmision >> would be possible. >> >> However, this transmission has a different gear ratio than my old >> transmission. My old transmission has a gear ratio of 2.14 (2.50 in reverse) >> and the new transmission has a gear ratio of 2.61 (3.16 in reverse). Since >> the gear ratio of the new transmission is higher, the prop would turn more >> slowly. But I believe it would be safe. >> >> Do you agree that it would be safe to use a transmission with a higher gear >> ratio? Or, do you see something important I'm missing? >> >> Other specs of the two transmissions are identical. Notably, the rotation >> direction of the two transmissions are the same. >> >> Any comment is greatly appreciated. >> >> Olivier Chatot >> C&C 38-3 >> >> _______________________________________________ >> >> Thanks everyone for supporting this list with your contributions. Each and >> every one is greatly appreciated. If you want to support the list - use >> PayPal to send contribution -- >> https://urldefense.proofpoint.com/v2/url?u=https-3A__www.paypal.me_stumurray&d=DwICAg&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=9w3G7Cf8YfQnrjmtuNxwDJYr3JMv9f1pAfgAJ9xXYQQ&m=AC2dODSM47hr4vAzmXP9EkP0VLDkXXrBUDfAjpE30AM&s=eeheZjpDsiFMg3A5qlYm38IsqCdXYT5Lo5ksBQ-tLJ8&e= >> >> > _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each and > every one is greatly appreciated. If you want to support the list - use > PayPal to send contribution -- https://www.paypal.me/stumurray >
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