converting from I/O to outboard- cost vs efficiency

[daddy]

hello. I recently purchased a 1975 21' fiberform cuddycabin with trailer. The boat is in fantastic condition. The motor must be replaced. My question is should I put in a new in/out board motor or seal the transom and mount an outboard on a jackplate? Which is more economically feasible? I am concerned about sealing the hole from the outdrive. Also would like to know the maximum hp for a boat this size. All input will be greatly appreciated.

[gonzo]

An outboard will take the weight far aft. It may cause porpoising and other running problems.

[daddy]

yes i understand but have seen many setups like that, an outboard on a boat that used to be i/o. what are the specs im looking for?????

[Raggi_Thor]

Why do you want to do this?
In NOrway, the smaller Mercruisers cost less than an outboard.
How many HP do you need?

[daddy]

150 hp at least...its a heavy boat and i want an easier engine to access and work on

[Raggi_Thor]

OK, I see.
You can compare weights at www.marinepower.com for example.
I suppose an outboard is lighter than an inboard, so moving the weight a little longer aft is probably not a problem.