Converting from inboard to outboard

[partgypsy]

I'm considering purchasing a 35' cruising boat with blown engines and pulling them and putting a modest sized (approx 150hp) outboard on the back.
I've owned a simliar boat before and it has everything I need for liveability. I am happy at displacement speeds.

The fuel tanks are in the stern and by moving them and the water tanks amidship I would have close to the same weight distribution. This would also allow the motor bracket to stay close to the transom for better engineering.
I'm sure there are other considerations so please fire away!

Thanks

[charmc]

Welcome, partgypsy.

If you use the search function to look up outboard conversion you should find discussions of this subject. There have been several successful projects done. Yours may be simpler since you are planning (it seems?) to operate only in displacement mode.

[kengrome]

I'm considering purchasing a 35' cruising boat with blown engines and pulling them and putting a modest sized (approx 150hp) outboard on the back.
I've owned a simliar boat before and it has everything I need for liveability. I am happy at displacement speeds.

Hi partgypsy,

150 HP will push 35-40 tons at displacement speeds. Are you sure you don't want a smaller engine?

[partgypsy]

You are right, but I wanted to allow for bad conditions, high winds and maneuverability in close quarters. The boat weighs about 18,000# (9 tons?) and would be somewhat less without the V8's. I would happily go less on horsepower if I knew the torque was there when needed. If I ran two 50's then could I cruise on one and then alternate?

[kengrome]

Two engines always cost more than one, and two 50 HP's will not produce the same thrust as one 100 HP. Maybe one engine about 70 HP would be best in terms of economy. You'll still have way more power than you need, but at least the engine size is more appropriate for the kind of displacement cruising you'll be doing.

What are the typical prices for 70 and 150 HP 4-stroke outboards these days?

[partgypsy]

New outboards are very expensive. Much more than the cost of replacing the big inboards. I was going to scout out rebuilt 2-cycle outboards... reduced cost and weight.

[Bullshipper]

Originally Posted by kengrome

Two engines always cost more than one, and two 50 HP's will not produce the same thrust as one 100 HP. Maybe one engine about 70 HP would be best in terms of economy. You'll still have way more power than you need, but at least the engine size is more appropriate for the kind of displacement cruising you'll be doing.

What are the typical prices for 70 and 150 HP 4-stroke outboards these days?

A 150 suzuki 4 stroke goes for $9,500 USD, mas controls and prop. Yamaha $10,000.

Goggle Eds Marine, as he lists good price for all major brands and sizes.