K&B 3.5 Engine Parts

[jpeck]

I'm brand new to model boats and nitro motors, but I have 30+ years as an auto tech and I'm pretty handy. I recently acquired and older home built? hydro with a K&B 3.5 outboard. After some extensive basic reconstruction(servo mountings, cables and the like) I felt i was ready to put the boat in the water. Not knowing of this forum, and after having problems getting the engine to continue to run, the only hobby shop in my area able to help me suggested an idle guard glow plug. Thankfully the engine ran, but my prop choice was poor. After filing and fitting a new prop and the engine running well, it suddenly seized. Using info from your site, I tore the engine down and determined that the cage from the rear bearing had failed and got sucked into the cylinder. Fortunately it suffered only other minor damage. Now to my question. When I tore down my engine, it has only one PTO bearing. Your diagram of the 8906/8907 shows 2, one fastened to the shaft and held by the PTO cover and the other below the cover? possibly in the lower unit. I intend to replace lower unit halves as well as all bearings and freshen the engine up as long as it's all torn down and need to know-do I order 2 PTO bearings? If I replace lower unit halves is my existing PTO shaft and cover reusable or are additional parts required? Answers to these questions will help me to decide to repair or possibly replace the engine. My engine is early; .750 diameter cylinder sleeve 12mm crank. Ser #K20128 Would really prefer to repair rather than replace, but durability and costs are factors. Thanx, ahead of time.

[MECOA]

You have a very early 3.5

All the parts we have only fit the later versions. You will need a new prop shaft assembly if you get new halves. If you use a new pto cover plate you will need 2 bearings.

Best bet is to buy the complete lower unit #50-8901 and a complete pto assembly #21-8923

https://shop.mecoa.com/shopdisplayproducts.asp?id=189

[jpeck]

Thank you for the info. I have a new prop shaft, teflon guide and flex shaft. I think the PTO assembly you suggested (#21-8923) and the lower unit halves will take care of that end. Thank you again and am looking forward to more contact in the future. Jerry