Originally Posted by luke1979
ive got mariner 20hp short shaft
You need to be a little careful as your Sib is rated to a 15. Check the maximum engine weight on your Sib plate and check on the manufacturers website the weight of the mariner. Some people including me do go a little over the recommendation. But that recommendation is capacity loading based on weight and stress from the engine on the transom. If it is significantly over you may risk causing damage to the transom or worse watching the engine sink to the sea bed. Only you can decide what is significant!