stern lifting prop?

[87blf125]

i have an 87 bayliner bass boat with a 1998 mercury 150 efi and am running a 23 pitch ss mercury prop with a sting ray hydrofoil, and am at 4800 rpm. my problem is the boat porpoises with out the hydrofoil, even when trimmed down all the way i can not even make it over 30 mph. with the hydrofoil i get 47 to 50 out of it but the boat tilts bad to the left. i have tryed mounting the motor higher and lowering with not much change. i know there will be many people who will say smart tabs of trim tabs, but like the hydrofoil i feel it is a bandaid on the problem and what i want to realy do is fix the problem. i just was wondering if a stern lifting prop is the way to go because the hydrofoil helps cuz it is lifting the stern. what props are stern lifting props, how do i know what one to get. i have tryed a 21 pitch ss and a high five prop also.
oh, and the boat porpoised with the original force 125 on the boat also.

 

[steelespike]

Re: stern lifting prop?

Some motors have an adjustable pin that sets the low trim starting position.
there are wedges that you can use to add or subtract initial motor bracket trim/angle.
Being an 87 I bet it has been rebuilt at some point .It may have a little bulge in the bottom near the transom.
Also if the transom was done maybe they made too straight an angle.i think they usually shoot for about 15 degrees.
Is the boat rated for 150?
Generally 4 blade props are considered stern lifters. you might try
reading up on various brands/models.
I realize it porpoised with the 125 but i'm sure you realize adding an additional 100+ pounds
on the transom isn't going to make it run with less bounce.
Have you tried to trim up even more to see if it can keep the bow up? of course you would have to try without the foil.
Have you tried a higher mount with the foil on I think its obvious the foil is having too much affect at speed. It sure isn't helping speed.

 

[87blf125]

Re: stern lifting prop?

Some motors have an adjustable pin that sets the low trim starting position.
there are wedges that you can use to add or subtract initial motor bracket trim/angle.
Being an 87 I bet it has been rebuilt at some point .It may have a little bulge in the bottom near the transom.
Also if the transom was done maybe they made too straight an angle.i think they usually shoot for about 15 degrees.
Is the boat rated for 150?
Generally 4 blade props are considered stern lifters. you might try
reading up on various brands/models.
I realize it porpoised with the 125 but i'm sure you realize adding an additional 100+ pounds
on the transom isn't going to make it run with less bounce.
Have you tried to trim up even more to see if it can keep the bow up? of course you would have to try without the foil.
Have you tried a higher mount with the foil on I think its obvious the foil is having too much affect at speed. It sure isn't helping speed.

there is no adjusting pin on my motor, and as far as i know the boat has not been redone. i have looked under the boat for a hook or buldge and can not see one. the reson i have the 150 on it" yes it is rated for a 150" is because the 125 started knocking and i figured it may keep the nose up if i had more hp. when i am not useing the hydrofoil it will not even get on plain jumping out of the water bad. http://www.youtube.com/watch?v=P-hPfx8DY3Q
http://www.youtube.com/watch?NR=1&v=3wXuLsFgrBE&feature=endscreen
these are 2 videos of what my boat does trimmed all the way down with out the hydrofoil.

 

[jimmbo]

Re: stern lifting prop?

Have you used a straight edge to check the hull for a rocker? Perhaps too much junk stored at back of boat causing heavy stern.

 

[steelespike]

Re: stern lifting prop?

I think the straight edge is a good idea. A neighbor had a 13 ft race boat that they had built in a tiny amount of rocker into
to try to keep it free of the water.didn't work it porpoised awful.
You couldn't see the rocker without a straight edge.
The boat in the video appeared to have something done to try to control the hop and it appears all it did was glue it to the water still hopping.
I guess you could try something like smart tabs or a 4 blade prop.
but sure looks like a design/hull problem.

 

[87blf125]

Re: stern lifting prop?

I think the straight edge is a good idea. A neighbor had a 13 ft race boat that they had built in a tiny amount of rocker into
to try to keep it free of the water.didn't work it porpoised awful.
You couldn't see the rocker without a straight edge.
The boat in the video appeared to have something done to try to control the hop and it appears all it did was glue it to the water still hopping.
I guess you could try something like smart tabs or a 4 blade prop.
but sure looks like a design/hull problem.

how far forward should i use a straight from the transom? and i guess if there is a rocker in it how do i fix it. also what do you mean by something done to the boat in the video? that is how the boat runs with out hydrofoil.

 

[steelespike]

Re: stern lifting prop?

Probably a 3 or 4 foot straight edge will work I think it would appear within the 3 foot area.
In the video it appears the boat is being pulled down after rising perhaps because the motor was trimmed all the way down,
or more than one fault in the hull,perhaps tabs of some sort.Maybe just speed.

 

[87blf125]

Re: stern lifting prop?

Probably a 3 or 4 foot straight edge will work I think it would appear within the 3 foot area.
In the video it appears the boat is being pulled down after rising perhaps because the motor was trimmed all the way down,
or more than one fault in the hull,perhaps tabs of some sort.Maybe just speed.

and idea how i can lift the boat up off my bunks to check under them, because i think if anywhere is not straight it would be where the bunks sit on the boat?

 

[steelespike]

Re: stern lifting prop?

Not knowing the style of the bottom;you could move the boat left or right on the trailer either by floating it and moving it over.
You could lower the tongue block the wheels rig a support to hold up the stern raise the tongue enough to take the weight off the bunks and check along side the bunks.
If the bunks have caused a problem it would likely cause a hook which would cause instant hole shot and the boat to lay down like it was glued to the water.
We're looking for rocker.I suppose bunks could cause rocker in another portion of the bottom from distortion.