Propping in Colorado

Chris5280

Seaman Apprentice
Joined
Jul 11, 2012
Messages
32
Hi guys- I'm kind of a newb, bought this boat last summer and learning as I go. Just pulled the outdrive to grease things up for the season and wondering if I should change propping. She really struggles to plane with more than 2 people. Sometimes even with only 2 people. Most of my boating is right at about 5280 ft above sea level near Denver, but I do make the annual pilgrimage to Lake Powell (~3650 ft). What makes sense? Here's my specs:

1) Performance issue you are trying to correct.
Boat has trouble planing, esp with more than 2-3 people aboard. Putting people in the cuddy helps;)

2) Current prop manufacturer, model, aluminum or stainless as a minimum.
Plastic/Composite 3 blade

3) Current prop diameter and pitch (required).
15x19a

4) Wide open throttle RPM and speed with an average load (very helpful)
4000 with 3/4 persons

5) Engine/drive make, model, year, and HP
Rebuilt 1988 5.0l GM 350 with OMC Cobra Outdrive (225-230HP)

6) Boat make model, year, length and weight
1988 Bayliner Capri 1950 19' - 2000-2500lbs?
 

blackhawk180

Petty Officer 1st Class
Joined
Jun 14, 2012
Messages
367
Re: Propping in Colorado

Let me be the first to thank you for following the guidelines for asking prop questions, Chris5280. Well done!
Having said that, I'm not the most reliable person to answer your question but it seems to me you are running to much pitch. The RPMs should be higher I think but altitude may be playing a part there. Personally, I had the same problem getting on plane and went from a 19p, 3 blade aluminum to a 14p, 4 blade stainless and thought I had a new motor. I was WAY over propped.
I'll be following this to see what our local experts say!
 

jestor68

Commander
Joined
Jun 12, 2012
Messages
2,308
Re: Propping in Colorado

Your 5.7 L rpm range is 4200-4400 rpm(1988).

Even though the prop selector calls for a 19 pitch at 5000 ft, it apparently is not working as you are only getting 4000 rpm.

Dropping to a 15 X 17 will get your rpm up to 4300-4400 rpm; right where it should be; and provide a noticeable improvement in over all performance, including time to plane.

A Doel Fin will cut your time to plane in half, and hold a plane at a slower speed. 00440.jpg
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Propping in Colorado

At 5000 ft your power is down about 15%. I don't think you should be struggling so much with a 19" prop.
Your still at about 200 hp with a 19ft boat. The 17 will surely help while you figure out if there is a shortage of power.
 
Top