Stainless That Much Better?

By: BW Staff

QuestionI was looking at an aluminum prop for my fishing boat, but I had a buddy tell me that under no circumstances should I consider getting one. That seemed like a big generalization.

AnswerEd note: We ran a column about props in February (The Truth About Props, p. 14). What follows are parts of that column by Alan Jones.) Stainless steel props enjoy a number of advantages, but aluminum props can be a better choice in a number of situations.

First, there’s the cost: Stainless steel props can be four times more expensive than their aluminum counterparts, and while they offer better performance, it’s not as dramatic as you might think. One advantage often cited for stainless steel is that aluminum props flex more, which is true to a certain extent, but aluminum props are also made thicker to compensate. What probably has more effect is that stainless steel is stronger, so the blades can be made thinner and more hydrodynamic. For boats with a top speed around 50 mph, the speed difference is usually less than 2 mph.

Being lighter, aluminum props are superior when it comes to carrying around a spare prop, and because of the reduced mass, there is less of a clunking sound when you shift than with a stainless model. Being less dense than stainless steel makes aluminum props more vulnerable to damage when they hit something, but the cost of a repair is far less. Whenever I’m in a new area that features shallow, unmarked areas such as oyster beds, I put on my aluminum spare just in case. But if it’s a lake with lots of submerged trees, I’ll use the stainless steel, since it can slice through most sticks without being damaged. Although it’s been bandied about that running a softer aluminum prop might protect your gearcase from internal damage, this has never been conclusively proven. In fact, most props have rubber hubs, which help prevent lower unit damage, so the prop material is, for the most part, immaterial.


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