Skinz motor cover on Yamaha SHO. Boat is new and had to take it to the dealer for some upgrades. The mechanic, who is excellent and a personal friend was very adamant about running the motor with the cover. Said it would lead to catastrophic power head failure due to overheating. Said Yamaha won’t warrantee if due to failure because of cover. Many have told me that they have used the cover for years and never had issues. Mechanic told me that if it happened he would have to let Yamaha know it was run with cover on it. Don’t know what to think.

Find a new mechanic.

Cant run with Factory Yamaha covers there not vented, You can run Tuff Skins

I run one on mine. Have 75 hours on a new Yamaha SHO 250. Motor will give you a warning if it overheats and put it into limp mode before it ruins the motor. As long as the water pump is working it shouldn’t overheat as outboards are water cooled. Mud daubers will ruin a motor guaranteed if they build a nest on the timing belt. I’ll take my chances with a vented cover.