Does anyone know how to quickly tell the difference between a Mercruiser 225II-TR and a 255II-TR drive without the serial numbers that apparently no longer exist? I have a Mercruiser Operation and Maintenance manual that came with my boat, but I'm not sure which I have. Ultimately I need to replace my drive so I need to know what parts to look for. Unfortunately I can't link pictures to this thread since I can't upload them to my Google Drive while on my work network. :-(

Thanks all!
-Dave

The tr is most likely a 2:1 ratio and can take a 20 inch diameter prop. The trs is 1.5:1 and will take around a 15 inch diameter prop. I believe the uppers are the same.

if thats what your asking

Hmmm... the plot thickens I suppose. I believe the prop on mine is roughly 18" across. In a call with Mercruiser based on the model year of the boat, the motor and transmission in the boat with serial numbers, they believed it was a 1.5:1 ratio.

When I get home I'll get some pictures of this thing posted up so everyone can get a visual.

If its got an 18 diameter prop its not a trs

I'm pretty confident it's a TR based on the manual I have for it. Just not sure if it is a 225 or 255. :-(

Anyone know where I could find a replacement drive? Essentially the entire thing from skeg to transom mount.

put a wrench on the prop nut. if it is 1-1/16ths, it is a TRS. if bigger, it is a TR. overpriced, but cases look good. make him an offer. only so many people looking for houseboat drives... https://www.ebay.com/itm/Counter-Rot...RY-O82&vxp=mtr why do you need whole drive? cases shot?

Those are #3's

What is a 3? Besides a speedmaster 3? In which case they are not overpriced.

Really old school (late 60's). Essentially a 3 SSM upper with a houseboat lower.

Genuine Mercury & Mercruiser parts. III 1968-1972 - 2373127 THRU 3002613

Check Cincinnati craigslist.there is one for $1200.