My Pontoon boat is ventilating. Changed prop

[kingfish166]

I just bought an 18' fiesta pontoon with a 50 merc. that ventilates. I put a new 12 1/4 x 9 qiucksilver alum prop on her thinking that would help. She'll run great at 5500rpm for a bit but any slight turn or movement of weight to the bow and she revs up. She has a 2008 50 hp Merc. 2stk (not a big foot) I added pics so maybe someone sees something I don't.

 

[steelespike]

Re: My Pontoon boat is ventilating. Changed prop

You have one hole remaining to lower the motor give it a try.
Also just the slightest trim change can improve venting problems or start them.Usually triming down will help but try both.
If still a problem try a 4 blade. See if you can fiod a pontoon dedicated prop.
usually larger diameter and big blades.

 

[jestor68]

Re: My Pontoon boat is ventilating. Changed prop

Lots of folks(including pontoon boat owners) use this little device to stop ventilation issues. It's called a Doel Fin.

 

[emoney]

Re: My Pontoon boat is ventilating. Changed prop

Slightest bit of chop and if it's trimmed up even a little will pull that prop out of the water on pontoons. Do you have a lot of weight forward.

 

[Texasmark]

Re: My Pontoon boat is ventilating. Changed prop

Lots of folks(including pontoon boat owners) use this little device to stop ventilation issues. It's called a Doel Fin. View attachment 164520

They are also sold under the Whales Tail brand.

Cupped props tend to hold better when there are opportunities for a prop to ventilate (Fact and I have experienced it). Most SS props are cupped. I don't know the cost of the tail, but it makes a lot of sense (I never ran one). If the prop can't develop a low resistance to air, it won't ventilate. This contraption seems to do a good job in not only helping stern heavy boats plane out but to prevent ventilation on things like toons. I have no experience with the latter. Just applying others comment having used them and some common sense.

Mark

 

[kingfish166]

Re: My Pontoon boat is ventilating. Changed prop

I just lowered motor to last hole and heading out to test her. Thank You All for the great info. I will check the fin out a 4 blade prop if she's still venting today. I'll keep you posted.

 

[kingfish166]

Re: My Pontoon boat is ventilating. Changed prop

Amazing how dropping motor one hole could make such a differance!!! She ran great!! Thanks a million!