Yes, most small, naturally aspirated diesels like ours have their max HP
near their maximum rated RPM, assuming air, fuel and other factors are as
designed. They may be capable of higher output beyond the rated max RPM,
but only for a short time, as most marine and industrial engines are tuned
for
When I look at my engine's manual, it gives a graph of horsepower to RPM.
The way I see it, the 2 are more or less directly related. If you are
unable to reach max RPM then you are by default also unable to reach max
horsepower.
Alternator output current is also a function of RPM. Lower RPM =
Two other points to consider, even if the new ratio allows you maintain
your cruising speed within a safe engine RPM:
1. You will be able to go slower while in gear at idle, which might be an
advantage. My speed at idle is a bit over 2 knots, which is a bit fast for
negotiating tight spaces, so I
Olivier,
Let me add a little info regarding the engine/gear/prop question.
Assuming a 19% higher gear ratio, if you can run the engine at 19%
higher RPM you will have identical performance of the prop/hull, as the
prop RPM will be the same. That means the power demanded by the prop is
: Olivier Chatot
Subject: [EXTERNAL] Re: Stus-List Fitting transmission with different gear ratio
Thank you for the comments!
I see that my understanding was basically correct. The shaft RPM will be lower
than before, and using a larger prop or a prop with greater pitch would counter
this difference
Thank you for the comments!
I see that my understanding was basically correct. The shaft RPM will be
lower than before, and using a larger prop or a prop with greater pitch
would counter this difference.
I'll update you later if I end up using the transmission with a different
gear ratio. I
Different gear ratio = different prop, so factor that expense in unless
you want to be like driving a car stuck in 2nd gear. Also make sure you
CAN fit the correct prop for that ratio.
Joe
Coquina
On 1/1/2020 4:43 PM, Olivier Chatot via CnC-List wrote:
Hi all,
I have an interesting
a CnC-List
Date: 1/1/20 4:43 PM (GMT-05:00) To:
cnc-list@cnc-list.com Cc: Olivier Chatot Subject: Stus-List
Fitting transmission with different gear ratio 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 3HM
: Wednesday, January 01, 2020 4:43 PM
To: cnc-list@cnc-list.com
Cc: Olivier Chatot
Subject: Stus-List Fitting transmission with different gear ratio
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
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
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
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
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