i like my boat, but wish it would have a higher top speed. what are the implications of installing engines which are rated with substantially higher horsepower?
There are a number of issues to be considered. If the replacement engines are heavier, is the increase in horsepower greater than that necessary to carry the additional engine weight at the current top speed of the boat? It is only the incremental power available after that necessary to carry the additional engine weight which offers the possibility to gain top speed. Replacing engines with higher horsepower ratings, but with no increase in weight offers the highest probability of achieving a noticeable gain in top speed.
Besides the engine weight to power issue just discussed, higher propulsive power requires an engineering review of drive line and propulsor size; the propeller diameter and other dimensions or waterjet may need to be enlarged. The gear ratio may change and shaft size may need to be larger; necessitating new struts and stuffing boxes. The structure of the hull and engine girders need to be checked to confirm that they will be sound for the higher speeds, for the new LCG the predicted running trim at top speed must be verified to be in a safe range (avoidance of dynamic instability, porpoising and chine walking).
