Yamaha outboard RPMs jumping

[Destroyer]

Originally Posted by Rusty5387

Okay I believe the problem is solved. It was not the prop and there is no such thing as a ventilation ring for a Yamaha outboard. Before launching the boat this spring I added an underwater light that I've been wanting to add for a few years now. Instead of purchasing a light that I would have to mount to the transom I opted for a light that screws into your existing drain plug. The light worked great, was very bright even in the darker water in the river near me and attracted bait fish to the boat almost immediately. I realized that is the only thing I changed on the boat this year prior to having the issue. We pulled the boat out and it looks like the light sticks out just enough to mess up the clean water flow that should be going right to the prop. I removed the light and put the regular drain plug back in and took it our for a quick run. The boat got on plane much quicker and ran great. I could not get it to ventilate again or a jump in the rpms. I appreciate the advice from everyone that replied but turns out it was my own fault. tight lines guys

Like the saying goes, you're never too old to learn new tricks. First, congratulations on figuring out the problem and second, thank you for sharing both the problem and the solution with all of us. I've never heard of something like that before, but you can bet that I'll keep it in mind if I ever want to mount an underwater light off the stern of my boat. Once again, thanks

[Pipe_Dream]

Wow, that's a new one on me. Glad you figured it out!

[SkunkBoat]

That must be a big light. I had a "Firewater" brand drain plug light on my V20 for years with no problems