99 21se f150 outboard height

Ponr · Apr 18, 2024

I have a cobia tower on my 21se and looking to try and find the proper height for the outboard.

Anyone else in the group with the same setup and which hole is yours mounted on? mine is on the second from the top.

I was running a Yamaha black sst 17p and getting 5400 RPM. added a permatrim and got 5500-5600.

Moved to a yamaha black sst 15p prop and getting 5600 rpm. I did notice it planing quicker with this prop. I I removed permatrim and got about 5800rpm but notice he boat doesn’t handle as good with the permatrim. With the permatrim the boat is more stable when running.

Attached are pics with the permatrim.

warthog5 · Apr 19, 2024

There is a problem.
You went out of sequenze.... You move the engine 1st.... Then you reprop.

Raising the engine will free the boat up... Less drag.... This will also raise the RPM max.

That is when you reprop to bring it in spec.

From your pix's... it will be one or two holes higher.... You want the anticavation plate at the surface.

The cobia tower really has nothing to do with this.

Ponr · Apr 19, 2024

warthog5 said:
There is a problem.
You went out of sequenze.... You move the engine 1st.... Then you reprop.

Raising the engine will free the boat up... Less drag.... This will also raise the RPM max.

That is when you reprop to bring it in spec.

From your pix's... it will be one or two holes higher.... You want the anticavation plate at the surface.

The cobia tower really has nothing to do with this.

I had moved it up a hole already. My anti cavitation plate is 1/2” above the V on the bottom of the hull. I mentioned having a cobia tower as it has the extra weight up top. And When cornering I do hear the engine tone change. I didn’t know that with my other boats as When I bought this one it had a cobia tower.I didn’t know if I can go up another hole. And I don’t know if taking turns at higher speeds would cause water flow issue to the lower unit.

Thank you responding I’m a newbie when it comes to boats.

Ponr · Apr 19, 2024

Here is a video I took last year

warthog5 · Apr 20, 2024

From what you just said.... It changes "Tone" in the when corning.

I would say no..... But there are variables... How hard are you turning and how much up trim do you have?
Not turning as tight at high speed and or trimming it down in the corners helps to not blow out and stay hooked up...This is what race boats do.

I'm not there, so I can't see/hear "Exactly" what is going on..... But a "Tone" difference would indicate that it is fixing to cavitate in that situation.

Ponr · Apr 23, 2024

warthog5 said:
From what you just said.... It changes "Tone" in the when corning.

I would say no..... But there are variables... How hard are you turning and how much up trim do you have?
Not turning as tight at high speed and or trimming it down in the corners helps to not blow out and stay hooked up...This is what race boats do.

I'm not there, so I can't see/hear "Exactly" what is going on..... But a "Tone" difference would indicate that it is fixing to cavitate in that situation.

Thanks Warthog! Well I went to work on the boat to get ready for the season and the bottom bolt is maxed out touching the bottom of the midsection mount on the transom. On the top mounting hole I’m in the 2nd hole.