Prop question

[slammer]

Boat-1800 Lund Tyee Motor-150 Merc 4 stroke Prop-Merc Tempest 19p stainless.

The prop has 3 holes with plastic inserts and says something about ventilation on it. What are these for? Can they be plugged or closed? The prop seem to "slip" a lot until you get the speed/trim just right and then it grabs. Not a big fan of stainless but it came with the boat. I think if these holes could be plugged it would work better. Anyone dealt with this kind of thing?

[delcecchi]

The holes allow exhaust gas to exit and let the prop slip some to get the motor revved up at low speed. You can plug the holes to see if that works better for you, or take them out. I don't know if you can use only 1 or 2 to get intermediate effects. I would go check on Merc's web site for info.

[Kyhl]

Yep, sounds like you understand the issue.

They can be plugged. If it is a Merc brand prop they make inserts with different size holes so you can tune it to your liking or plug them completely.

[hydro]

That prop is technically a “Tempest Plus” and as mentioned above it is designed so that you can tune the amount of exhaust blowing through the hub to free up the prop during planing or “hole shot”. Since your motor has no transmission, when you first hit the throttle it is way below the power band and the Tempest Plus will ventilate and allow the motor to spin up and make horsepower.

I have that prop on my boat and I tuned it so that I get reasonable slip as I accelerate, but not so much that the prop blows out when the boat planes over. When you have it right it will do as you described, ventilate to spin up, then gradually bite the water and push the boat onto plane. You need a couple of different hole size inserts to do this and an hour or so at the beach to try different combinations but it’s really quite easy to do. Too little hole area and the motor lugs to get the boat on plane, and too much will “blow out” when the boat planes out or when you turn tightly with the motor trimmed up. Good luck!

[slammer]

Thanks for all the info. I'll play around with it this weekend and see what happens.