Transmission ratio

[Sutric]

Greetings, I'm shopping for a propeller for my 1993 Hunter 33.5, with a Yanmar 3GM30F and a Kanzaki KM3P. The issue I'm having is that everyone wants to know the gearbox ratio and I can't find it! For reasons unbeknown to me it's not stamped on the tag! Do any of you fellow 33.5 owners with a 3GM30 and a KM3P know what your ratio is?

 

[Tally Ho]

Supposed to be right there…I can make out a faint “2” I think.

This is what it should look like…


I don’t know what the options were on the KMP3.

Greg

 

[JoeWhite]

It is 2.62 that appears just below the model number

 

[Tally Ho]

That is my KM2P….

But I found this reference…2.36:1

https://shivglobalmarine.com/detail/yanmar-km3p-1-kanzaki-transmission-2-36-1

But I don’t know how many other options were available.

Greg

 

[Tally Ho]

I also see references to a 3.20:1. And a 2.61:1 gearing.

I wonder if you can put more light on the tag or clean it with something to try and make the gear ratio more visible?

Lastly, since you can make out the serial number, maybe a call or email to Yanmar / Kanzaki can confirm which gear ratio your tranny has.


Greg

 

[dlochner]

There isn't much room, however, you might try a "gravestone rubbing" on the model number. There is a faint mark and it looks like a 2 at the end.

Or, contact Yanmar, see if they can help.

 

[Ken13559]

Would it work if one were to engage the forward gear and rotate the crankshaft manually by 1 turn or any number and count the rotation of the gearbox output shaft coupling? Decompressing the pistons would make turning crankshaft easier.

 

[Davidasailor26]

Would it work if one were to engage the forward gear and rotate the crankshaft manually by 1 turn or any number and count the rotation of the gearbox output shaft coupling? Decompressing the pistons would make turning crankshaft easier.

I like this idea if the old stamping can’t be recovered. In one rotation it might be hard to tell whether the shaft has turned 2.62 rotations vs 2.36, but if you can turn the crank a few times the exact ratio will get clearer.

 

[Claude L.-Auger]

I cannot attach the Service manual for that transmission as it is too large but it does show a ratio of 2.61/1. My 3GM30F with that same KM3P tranny shows a 2.61/1 ratio as per the attached pix. FYI on my 34, I have a 3-blade 15 X 11 RH prop which when running at 2600/2800 RPM gets the speed up to 6.5 knots (flat water no head wind!). Besides the tranny ratio, the prop supplier should ask your max RPM. Hope it helps.
Last minute edition: I have found a way to downsize the PDF file on the Yanmar Kanzaki KM3P transmission and uploaded it to this site. Look under Owners Resources General Downloads.

 

[Sutric]

Thank you! This is one of the reasons I love this site!
Rich