Is this prop hurting performance?

[SnookHunter]

I have a 16' lowe sea nymph aluminum boat with a 05 25hp yamaha 4 stroke with a aluminum michigan wheel 9 7/8 x 10 1/2.

Now with the setup just like that I could run 27.5mph by myself with a light load(gps verified) And 25mph with 2 people and a full load. I also didnt have a tack at the time, so no clue on the rpms. The av plate was also 2.5 inches below the bottom of the boat. I bought a Bobs machine mini manual jack plate and raised the motor so the AV plate is even with the bottom of the boat. And the setback is 5 inches. But now my top speed has decreased by a fair amount. I just purchased a tiny tach, so I could check the rpms. I can only reach 26.4mph by myself with a light load and the rpms reach 6140. With a 2 people and a full load i can only get 22.8mph at 6040rpms. I can raise the motor another inch if need be. What could be the problem? I thought raising the motor would mean less drag and a bit more speed. Is the prop causing the problem?

 

[Texasmark]

Re: Is this prop hurting performance?

Sounds like it. Sounds like it is ventilating (sucking in air being too close to the surface) which is causing your rpm's to increase and speed to drop. Yes, the prop is at fault after you fauted it by raising the LU up. I like your original numbers where you can add people to the boat and have little effect on speed. Sounds like you are (were) setup pretty good for your rig.......before you raised it.

I think I'd put it back where it was and leave it alone; unless you have money burning a hole in your pocket. If so, Kenny (Walleyhed) on this forum, can help you get rid of it.......not that he will spend it for you; he will show you where you can spend it.

Mark

 

[SnookHunter]

Re: Is this prop hurting performance?

Ya it was setup pretty good. But it sprayed water all over the engine. And as low as the motor sat if a decent wave from another boat hit me from the back it would come over the engine hood. And you wouldnt believe the salt build up Ive had to clean off the engine block.

I'm tempted to put it back the way it was. However I've already come this far and have the holes in the transom so I might as well use them. Can anyone else chime in on where to start?

 

[SnookHunter]

Re: Is this prop hurting performance?

Anyone?

 

[walleyehed]

Re: Is this prop hurting performance?

It sprayed water on the hood because it was mounted way too low....typical.
If you're not stuck on aluminum, I'd look at a Stiletto Triad 10-1/8X11.

 

[SnookHunter]

Re: Is this prop hurting performance?

Where would be a good place to get a Stiletto triad? Nobody around here carries any ss props for my small outboard.

 

[walleyehed]

Re: Is this prop hurting performance?

Snook, email me at ktsander@st-tel.net
We can't post the links on the board.
Kenny