Not sure how well the engine will run on a jack plate running higher then it should, most bay boats with them have small tunnels designed into the hull to allow water to flow to the prop and such to allow the engine to operate correctly. Being that the engine on a 225 would be on a bracket, this will allow better flow to the engine if raised.
Unfortunetley, I do not feel this is worth it and will solve your issue, if you have a bracket, the jackshaft will raise the engine, but will not prevent floating debris from hitting the engine at all. Personnaly I do not think the investment is worth it at all. In a chop or swell the engine will likely cavitate a bit and not dig into the water well, you might see a good drop in fuel efficiency and speed, your gain would only be in flat flat calm conditions. In flat calm conditions you will see better speeds and efficiency because less of the lower unit is in the water creating drag, but that is assuming it is getting enough flow to the engine in the first place.
Also, you will require a totally new propeller if you go to a jack shaft, it might be just a pitch change, but could be diameter as well since the engine will reach max rpm faster with less drag created. Jack plates are also known for applying more stress to a transom with how they are mounted, it is highly recommended to have the transom reinforced to accomodate a jack shaft. By mounting the engine higher you adjust where the load on the transom is applied, and the jack plate will mount to the original holes where the engine was mounted, applying new forces onto the transom and bracket that they was not designed to accomodate.
Adding one is a big job, it is not as easy as just bolting it to the bracket and then bolting the engine on, anyone who says it is is wrong or just wants to sell their product.
Also, resale of a boat modified to handle a jack shaft would be hard, you would need to find someone who knows nothing about boats basically, 98% of buyers will see if and run or wonder what was wrong with the boat that it needed one and no others did.
Personally I would not add one, but if you feel it is necessary to boat safely in your waters have at it, just understand all that will be required for your boat to handle the jack plates safely.
