CD 27 Engine - Do I have a YSB8 or YSB12?

[Tailwind]

Hi Cape Dory forum folk,

This is my first post. I'm the happy owner of a new-to-me 1977 CD 27 "Sea Lilly". I'm taking care of deferred maintenance: getting stuck seacocks moving, new hoses on all seacocks, new belts on the engine, lifelines, new compass, canvas repair, etc. I'm finding a wealth of helpful info here on the forum.

The boat seems under-propped. At 2200 RPM on flat water she'll make 2.3 knots. Prop is a 2 blade. I'm not sure of the size/pitch. Bottom of the boat was cleaned a month ago.

Before I shop for a new prop, It would be good to know which engine I have. From what I read, the boat would have probably come with a Yanmar YSB8. However, the ID plate on the transmission reads "YSB12". I haven't found a serial number on the engine block. Is there a way to be sure the engine is a YSB12? Could I have an YSB8 with the transmission from a YSB12?

ID tag on transmission:





Thanks!

[fmueller]

Well that badge is pretty convincing -

Here is an old Yanmar product sheet. The 12 is dimensionally larger and the mounts are a little larger as well ... you should be able to determine with carefully measuring engine width for instance ...


http://sailingthanksdad.com/documentati ... ochure.pdf

[Tailwind]

Fred,

After carefully measuring, it's pretty clear that I have a YSB8 engine with the transmission from a YSB12.

Thanks so much for your help!

Steven

[Walter Hobbs]

Greetings,

I have CD 27 hull # 35. YSB8 original to the boat as far as I can tell. 2 blade prop easily pushes her to 5 knots. You say bottom is clean does prop have any growth? I don't have prop pitch or diameter handy, my notes are on the boat. I'll check. Interesting puzzle. Different gear ratio in YSB12 transmission??

[fmueller]

Good guess Walter. Wonder if a previous owner fit the 12 transmission as a repair and inadvertently raised the reduction ratio. That could account for lack of speed. As if you are stuck in 1st gear - prop never spins fast enough. A very powerful car for instance would not have top speed if it could only use first gear. Acceleration maybe.

Even wilder guess. What if there’s a wrong handed prop mounted and the forward and reverse control cables are swapped. Some transmissions have really steep reverse reduction.
L

[Walter Hobbs]

Fred,
Per the data sheet you posted, looks like reduction ratios for both engines are the same. Guess that's not it.

[Tailwind]

@fmueller Interesting wild idea. I checked the movement of the shift lever/transmission lever. It moves as it should - moving the shift lever forward puts the transmission into ahead; moving it aft puts the transmission into astern.