Willing to play the prop game

[Reming870]

OK, Here is what I have learned and what I have. Overall I want to improve performance to quicker plane and maneuvering in tough seas.

Current setup:
1979 Grady White Kingfish 254
2009 Pleasurecraft 5.7 L / (MPI)
2013 SEI outdrive / (Alpha 1 Gen 2)
Prop: 16D 13P Quicksilver
4000 RPM = 22 knots with an additional 1100 lbs people and gear. This is cruising speed for me with little room to improve, if I go slower I lose plane easily. I can get to about 4400 RPMS and 25 knots with a tail wind on a flat day at best.

I have tried the 16D 11P prop and the hole shot is great but the RPM's are high to get the same long distance speed.
I have tried the 16D 15P prop and can barely get to plane after a few minutes.

I would like to keep similar performance that I have with the current prop for long distance runs but I do struggle with adjustment when seas are 3+ feet as I am near WOT and have little room to manipulate.

Typical trip for me is 20-40 miles offshore. Bottom and shark fishing primarily.

Any suggestion to improve this performance?

 

[steelespike]

Is this boat intended to plane?
Do you know the gear ratio?
Your saying 4000 @ 22 is it with 1100 lbs aboard?
What is the lightly loaded gps speed and rpm?
I'm no expert with these big rigs but seems to me a 260 hp 5.7 could produce speeds over 30.
My info indicates the MPI is good for 5,000 rpm And the rpm range is 4400 -5000 so your not even within the range.
Your motor is not running up to par.
That boat is available with a 165 motor I think 100 more hp should do better.
If you boat mostly with the 1100 lbs you need to prop to be within the rpm range at wot.
I think if your motor was healthy your 13 or even a 14" prop should make the rpm range .
Your struggling to make planing speed So your going to struggle to maintain speed when battling swells.
The easier for your motor to rev the easier it should be to control.I would;d stay 4800.
You don't need to run at that rpm.
A 4 blade prop should help.
Do you have trim tabs?

 

[Scott Danforth]

WOT should be 5000 RPM as steelespike indicated.

What is your actual WOT RPM, GPS speed and gear ratio?

from the prop sticky: http://forums.iboats.com/forum/gene...p-questions-and-topics/295058-read-this-first

ESSENTIAL DATA REQUIRED
When posting a question about propellers, you cannot get a reasonable answer unless you provide the following information in your post: Items 1-4 are essential for meaningful response to most questions.
1) Performance issue you are trying to correct.
2) Current prop manufacturer, model, aluminum or stainless as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle RPM and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP
6) Boat make model, year, length and weight

based on http://boatspecs.iboats.com/Grady-White_Boats__254_King_Fisherman__1979/bp/66b37852, your boat weighs 5100.

I would assume that you would be in the 15"-15P range

 

[Reming870]

Good weekend last weekend shark fishing. Seas only around 2-3 ft so I could get the WOT easier. I was able to get to 5000 RPM at WOT but it took a bit.

5,000 RPM gave me 29 knots. I also neglected that there is a custom enclosure (wood and fiberglass) built on this boat. I am estimating that to be an additional 1500 lbs.

So on top the listed weight 5100 lbs, I would add 1100 lbs gear and people, 1500 lbs for enclosure and 900 lbs fuel when full to total 8600 lbs.

 

[Reming870]

Pic of boat enclosure

 

[Tail_Gunner]

The fact you got to 5000 indicates your probably on as far as pitch is concerned..with one little side issue..your at 21 percent slip. For myself that leads to two problems one the prop slips badly so it is no place to start from. Going to merc's prop selector show the flowing

No results.
Alpha 4®	Mercalloy	4	15	16	RH	834850A45
Black Max®	Mercalloy	3	15.5	15	RH	78116CP1
Black Max®	Mercalloy	3	16	16	RH	16440CP1
Black Max®	Mercalloy	3	16	16	RH	16440A45
Black Max®	Mercalloy	3	15	17	RH	832828A45
Enertia®	X7 Alloy	3	14.7	16	RH	898992A46
Enertia®	X7 Alloy	3	14.5	17	RH	898994A46
Enertia®	X7 Alloy	3	14.2	18	RH	898996A46
Revolution 4®	Stainless Steel	4	14.625	15	RH	857022A46
SpitFire®	Mercalloy	4	14	17	RH	8M0084494
Vengeance®	Stainless Steel	3	14.5	15	RH	16312A46
Vengeance®	Stainless Steel	3	14.5	17	RH	16314A46
Vensura®	Stainless Steel	4	14.5	17	RH

• Boat type: Offshore Fishing
• Usage: Mid range cruise / fuel economy/0 ft
• Engine Manufacturer:
  Mercury
• Engine Type: Sterndrive
• Engine Year: 2009
• Number of Engines: One
• Engine Family: Small V8
• Engine: 350 MAG MPI
• Drive / Gear Case: Alpha 1.47 Gear Ratio

DETAILS

• Calculated Pitch: 13.08
• Calculated Weight: 8,600.00
• Calculated Engine RPM: 3,333.33
• Calculated Boat Speed: 37.61