Can a hydrofoil raise RPMS at WOT?

[Toad Snatcher]

I need to get my rpms down and my boat had a hydrofoil on it when I bought it. Just wondering if it can raise rpms at WOT?

 

[JimS123]

Re: Can a hydrofoil raise RPMS at WOT?

No. You need a new prop.

 

[Fleetwin]

Re: Can a hydrofoil raise RPMS at WOT?

I need to get my rpms down and my boat had a hydrofoil on it when I bought it. Just wondering if it can raise rpms at WOT?

Possibly. Especially if the hydrofoil is causing prop cavitation.

 

[Toad Snatcher]

Re: Can a hydrofoil raise RPMS at WOT?

How can I tell if this is occurring?

 

[JB]

Re: Can a hydrofoil raise RPMS at WOT?

No. You need a new prop.

What Jim said.

 

[IamCanadian]

Re: Can a hydrofoil raise RPMS at WOT?

To answer you best, What is your speed and RPM @ WOT what prop are you running and what motor? How is your motor trimed? Where is your anti vent plate in relation to your skeg? Higher, lower, Level?

 

[JimS123]

Re: Can a hydrofoil raise RPMS at WOT?

To answer you best, What is your speed and RPM @ WOT what prop are you running and what motor? How is your motor trimed? Where is your anti vent plate in relation to your skeg? Higher, lower, Level?

If his anti vent plate is lower than the skeg the boat must be capsized!

 

[Another retired guy]

Re: Can a hydrofoil raise RPMS at WOT?

I need to get my rpms down and my boat had a hydrofoil on it when I bought it. Just wondering if it can raise rpms at WOT?

In theory - yes. The hydrofoil lifts the stern thus reducing hull friction. Less friction gives more speed. More speed reduces prop resistance thus increasing rpm's. In theory . I don't think it makes much difference though.

 

[IamCanadian]

Re: Can a hydrofoil raise RPMS at WOT?

If his anti vent plate is lower than the skeg the boat must be capsized!

HA HA My bad....keel is what I meant lol. Good catch

 

[Fleetwin]

Re: Can a hydrofoil raise RPMS at WOT?

How can I tell if this is occurring?

Does the prop show signs of pitting?

 

[Mi duckdown]

Re: Can a hydrofoil raise RPMS at WOT?

Have you removed the hydrafoil? the reson I ask IS, in the first Post Motor HAD a hydrafoil.
If so, post Pics of your motor in relation to your transom.
Did I miss what size boat and motor?

 

[Toad Snatcher]

Re: Can a hydrofoil raise RPMS at WOT?

It is an 89 50hp Johnson on a 17ft bass tracker. Have not removed the hydrofoil. Going to do that the next time out. The prop seems to be missing paint on the outsite 1/2 inch of each blade. I have no clue if this is a sign of cavitation or not. I will take a pic of it today. Thanks to all of you for your help.

 

[5150abf]

Re: Can a hydrofoil raise RPMS at WOT?

Still need to know current wide open throttle RPM and what prop you are running, should be 5000-5500 if you are in that range you are good but we will need your current prop size to tell you which direction to go with it.

How did you determine you are under propped?

It will be somewhere on the prop, stock OMC is between the blades on the hub others in various places.

The missing paint is more then likely from running across a sand bar, I would imagine the skeg is also missing some paint.

I have a similar set up and run a 12-1/4x13.

 

[ondarvr]

Re: Can a hydrofoil raise RPMS at WOT?

The proper use of a foil allows you to raise the motor higher, this may result in higher RPMs and a higher top speed. This may or may not be what you dealing with. Like others said, You will need to supply WOT RPMs, speed, and a few pics of the the current setup before good answers can be given.

 

[Toad Snatcher]

Re: Can a hydrofoil raise RPMS at WOT?

6500 RPM at WOT and volt meter reading 16 volts. If I back it down to 5500 rpm the volt meter reads a little over 12 volts. The prop is an 11 3/4 x 17. The speedometer reads 33-34 mph at wot.

 

[Toad Snatcher]

Re: Can a hydrofoil raise RPMS at WOT?

Here are some pics.

 

[Fleetwin]

Re: Can a hydrofoil raise RPMS at WOT?

Check the accuracy of your tachometer. On the back, there is a switch. It should be set on "6".

Your Wide Open Throttle (WOT) RPM's should be 5500 with an average load. I wouldn't worry about 5800 or so but 6500 is too high.

16 volts is not uncommon. That is an unregulated charging system.