Dedicated To The Smallest Of Skiffs banner

1 - 20 of 22 Posts
T

·
Guest
Joined
·
0 Posts
Discussion Starter #1
I have a light SUV17 with a Mercury 25hp 2 stroke, power tech cupped 3 blade prop, TSG custom manual jack plate and a Bob's cavitation plate.

My pin is in the 2nd from the bottom on my motor and my cavitation plate is 4" from the bottom of the hull.

When I'm running the cavitation plate is out of the water with just the downward fins in the water. I have no problems with blow-out at all and since I have been running this set-up for over 50 hours and have not killed my engine I would guess I'm getting enough water pressure. I get much better hole shot in the 1st pin setting, but it does not feel as nice as the 2nd.

Does it sound right where the cavitation plate is?

Do I go higher on the jack plate? I have no water pressure gauge.

The hull is flat bottom with no tunnel and the jack plate has a 4" of set back.
 

·
Cert. Yamaha technician
Joined
·
4,330 Posts
4 inches is alot for a flat bottom skiff imo. But definately do-able. Let me ask you this, if you run in a condition with swells, say for instance behind a big boat.(we all know how big boats prop wash makes those swells directly behind the boat, NOT ThE WAKE. Does it blow out when the rear of the boat lifts in the swell? If not i say try higher. I have mine set up so it just starts to blow out when im running in those small swells to fast.
 
T

·
Guest
Joined
·
0 Posts
Discussion Starter #3
4 inches is alot for a flat bottom skiff imo. But definately do-able. Let me ask you this, if you run in a condition with swells, say for instance behind a big boat.(we all know how big boats prop wash makes those swells directly behind the boat, NOT ThE WAKE. Does it blow out when the rear of the boat lifts in the swell? If not i say try higher. I have mine set up so it just starts to blow out when im running in those small swells to fast.



I will put some pictures up as soon as a can. I have zero blow-out behind boats, 2' swells anything I have come across.
 

·
Living & Dying in 3/4 Time
Joined
·
2,558 Posts
That's good to hear BN. I run mine about the same height as yours on a normal basis and at times over 5" up. No blow out on normal running, chop or swells, however, running the marsh with the plate up, making sharpish turns ~25mph it will suck a little air.

I'm interested to see how your static plate height works out.
 

·
> PRO STAFF <
Joined
·
7,516 Posts
You definitely have it mounted as high as it'll go...
How long did it take to find the highest setting?

SUV 17 and 25 hp merc 2 smoke






As to why it works, you have to remember running angle.
Tilt the bow up 5 degrees and the red line is the keel line extended.
The yellow line is the level line when the hull is on plane.
the blue line is the approximate top of wake line as it rises off the bottom of transom.

 
T

·
Guest
Joined
·
0 Posts
Discussion Starter #6
Thanks for posting those pics Brett.

I got lucky with the height as I mounted the Jack Plate high before I realized the transom is 18" after I had it cut down 3".

I think it's pretty dialed in and I'm running ultra skinny. Next up is a torque tamer as I'm pulling pretty good to the right.
 

·
Cert. Yamaha technician
Joined
·
4,330 Posts
Holy crap that looks high. For some reason i cant get mine near as high as that.. And i have power trim.. If i could ide probably break 40mph... Almost makes me think im seriously doing something wrong??? Ive been doing thi for some time but if anybodys got any tips, shoot em at me
 

·
> PRO STAFF <
Joined
·
7,516 Posts
CR, the only way to run shallower is to throw money at it. You already know that... ;)

Power jack plate-check
Power trim and tilt-check
Power trim tabs-check
Nose cone-check
Low water pickup-check
Cleaver prop-cash
(ran out of checks)
 

·
> PRO STAFF <
Joined
·
7,516 Posts
BN, do you think you might pick up some speed if you trimmed out the engine
so that the anti-ventilation plate was level with the yellow line?
It'd move the prop and inlet further back and the skeg would be running shallower

Tilt the bow up 5 degrees, the red line is the keel line extended.
The yellow is the level line when the hull is on plane.
The blue is the approximate top of wake line as it rises off the bottom of transom.


 
T

·
Guest
Joined
·
0 Posts
Discussion Starter #13
I'll get some video running as I don't even know how it looks. I'll also try one or 2 pins up and see what my MPH is.
 

·
B.S.
Joined
·
405 Posts
I'm watching this thread like a hawk. I added a jacked up jack player to the SUV I'm getting relatively soon and I need to run uber skinny.... :cool:

I'll have a 30hp fourstroke on the back.
 

·
B.S.
Joined
·
405 Posts
The boat is still at Mel's. I won't get it until the end of the month.. :'(

I'm ready to see it!!
 
T

·
Guest
Joined
·
0 Posts
Discussion Starter #17
I went out on Monday with my wife on the IRL by Titusville. Water and weather were awesome! The river is now clear and can see 4' down no problem.

I shot some video of the cavitation plate while running. You can see that it is out of the water and only a small part of the fins are underwater.

I was only out for 3 hrs or so and did not rise the jack plate or tilt the motor from were it's been at.

I got home put a level at the bottom of the hull and measured from the top of the cavitation plate to the tip of the skeg. It came out to 9" which for a skiff without a tunnel is pretty darn shallow.

I'm going to be buying another prop soon.
 

·
B.S.
Joined
·
405 Posts
What does it take to run a prop like that?
 

·
Living &amp; Dying in 3/4 Time
Joined
·
2,558 Posts
Dave that's on a Yamaha 25 2stroke. Cleaver blade style designed to run only partially submerged. Typically a slow hole shot but runs out like mad on the top end.
 
1 - 20 of 22 Posts
Top