Seacraft 32. Twin 200 Yamaha 4 strokes!

[captbone]

Originally Posted by FishStretcher

The torque on the the gears will be the same, true. But the force from the higher thrust at lower speed will be resolved in the lower unit bearings. And the motor mounts. I don't design lower units, but I have a suspicion that this is something you can get away with for a time. Or at least get home and then tear down a LU and put new bearings in it. I suspect the gear teeth will be fine.

Just a guess.

The thrust is all the same. If the thrust was higher the boat would go faster. The speed in which the gearcase travels through the water or the amount of thrust producted at a given RPM is not relevant since the max thrust would be identical at WOT as long as it can reach the recommended wot rpm and peak hp.

Outboard engines that push barges, heavy boats, or tow a lot do not have a decrease in life simply because the engine can only product so much load, torque and thrust. Propped correctly, their is no increase in wear, tear or load regardless of what the outboard is pushing or the prop. Max is at WOT regardless of prop.

Just my 2 cents. I would gladly chip in to see the owner run a 13 pitch prop on one of the twins to see it break 30mph.