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25 HP to 40 HP Tiller - Mounting Help

P

pletz

New member
Greetings everyone! I have a question I am hoping you all can help me with. I have a 16' Alumacraft Backtroller with a 25 HP tiller motor on it. I am looking to increase to a 40 HP tiller. Currently, the 25 HP is mounted with the thumbscrews only (not bolted through the transom).

My question to everyone is, do I need to make any special considerations when mounting the new-to-me 40 HP motor? My thoughts are the steps are:
  • Remove 25 HP
  • Place 40 HP on transom
  • Confirm motor is sitting at proper height
  • Mark holes, drill holes
  • Seal transom wood inside the holes
  • Bolt it up
  • Seal from the outside
  • Go fishing

Am I missing anything critical? Other questions I have for the group relate to the concept of going from a 25 HP to 40 HP tiller. What are the pros & cons in your experience?

Thanks in advance everyone!
 
timguy said:
Welcome. Good morning. What kind of motor is it? What year, and 2 or 4 stroke?
Click to expand...

Good morning, thank you! I currently have a 1989 2-stroke Mercury 25 HP and am looking at purchasing a used 1985 40 HP Johnson (J40TELCO), also 2-stroke.
 
That motor can be clamped down with it's "thumbscrews". For me, since we put the motors away in the shed each fall, parking the boats outside, I never add more bolts for the mounting. Our 50 hp Merc, 2 stroke, however....is bolted. I feel that 40 hp is max for "thumbscrewing" only and no additional bolts being used. Been running unbolted 40's for 55 years without 1 problem. We check often and snug up as needed. Always been uneasy about drilling holes through transom, especially when we are always switching around motors and storing inside. If you intend to keep the motor on for several years, then you can certainly mount with stainless steel hardware, making your seal with a good RTV or Seal All, as you mentioned.
 
Thanks for the input. I’ll be picking up the “new” motor on Monday. Looking forward to swapping it out and, hopefully, testing before it gets too cold out.
 
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