If a pull-up outboard motor bracket is rated for a 20-hp, two-cycle motor, then why couldn't it handle a 9.9-hp four-cycle engine?
Sue & Larry respond:
In the past, brackets for outboard motors were categorized according to the horsepower and weight that they could safely handle. That was in the days when there were only two-stroke engines. Today, four-stroke engines are becoming more and more popular. These engines are larger in size and weigh considerably more than their two-stroke counterparts.
So, when sizing an outboard bracket for a four-stroke engine there is more to consider than just weight, size, and horsepower. Four-stroke engines produce much greater torque than a similar sized two-stroke engines. For this reason, along with the greater weight, manufacturers have found it necessary to beef up their motor brackets.
The weight of a 9.9 hp four-stroke engine is approximately the same as that of a 20-hp, two-stroke, so based simply upon weight, you’re already at the upper end of the bracket’s capacity. Not knowing the exact torque of these two engines, we feel that you’d be best served to follow the manufacturer’s suggestion. And, apart from all the other reasons, it’s always more difficult to use a motor bracket for lifting and lowering when you’re at the upper end of its designed capacity. Good luck to you.