Prop questions

[jmoshier]

looking for some questions and answers?

1989 Wellcraft 192 classic cuddy,4.3 175hp OMC
out drive weight 2550
current prop; no name aluminum 141/4 x 21 serial number 391202.
plows in the water pretty good takes about 5 seconds to plane and 20 seconds to top speed of 40 mph by speedometer and tach is at 4600 RPM, RPM range 4400-4600. looking for better hole shot and better top speed, more efficient prop, aluminum or SS. New to iboats (great forum) and this is my first boat, tubing and skiing are on the agenda probable always have 4-5 people on board. I have been looking at the Lexor SS 19 inch, if you need more info please let me know.
thank in advance

Jim Moshier

 

[WillyBWright]

Re: Prop questions

20p Alpha 4-blade aluminum or High Five stainless in the same ballpark. IMHO

 

[walleyehed]

Re: Prop questions

391202 is an OMC original alum...
If you want hole-shot AND some speed, you're likely gonna need to stay with a 3-blade and vent it.
The Lexor is a good choice and has alot of load carrying capabilities, and yet still holds it's own on top.
For speed you need lift, the Lexor has good lift for a sterndrive prop, but the 19 may put you 100-150 over your max RPM range....not a "major" issue, but a vented 21 may be a better answer.

 

[jmoshier]

Re: Prop questions

Willy,
the High 5 was an option thanks for the input, as far as 20p Alpha 4 have you had experience with that prop and how did it do?

Kenny,
When we purchased the boat it had 2 - 141/2 aluminum 19p both 391201 they were dinged/broken. I was guessing the previous owner was proping up for speed not efficiency. I'm still new to boat terms, venting a prop means what, and who can do that? I think I read that you had/have a Wellcraft, what was it and what prop did you end up with on it and why.

thank you for your replys
Jim Moshier

 

[walleyehed]

Re: Prop questions

21ft wellcraft cuddy with a 5.7
We run a 19 for skiing/towing and a 21 for speed/best cruise. both props are the same design...one is a Mirage+, the other is a Lexor.
Venting is drilling holes aft of the leading edge of each blade to allow some exhaust to "vent" during hole-shot to get the R's up and help move the load quicker...
Someone on here had an excellent drawing of hole placement...you might search "drilling a prop" or "venting a prop".

 

[jmoshier]

Re: Prop questions

Kenny,
I'll check and do a search for prop venting. What speeds can you attain with your 19 and 21 props.

Jim Moshier

 

[walleyehed]

Re: Prop questions

Well, most will tell me I'm nuts, but we turn this 5.7, 6000RPM with the 19P. Actually, we've seen 6100 with it.
the 21 will turn almost 5800, but we run about 5500 max.
Speed-wise, the fastest I've seen, and I don't remember which prop (I've had about 50 on this rig, testing), but I "think" it was a 23 Tempest, and hit right around 55MPH. I'd have to look back at my books and see for sure...I do "most" of my testing with the 18ft alum with the 200.

 

[jmoshier]

Re: Prop questions

double post

 

[jmoshier]

Re: Prop questions

Kenny,
Well I have looked and looked and am unable to find anymore info on prop venting, So if you can help me out I would be appreciate it. I was leaning towards the Lexor 19p till you suggested the vented 21p. it sounds to me to work like a stall converter in a car. the location of the hole and the size of holes are of interest to me. Best I can figure out is just aft of the blade and approx. size of about 3/8 to 1/2 inch in diameter.

thank you

Jim Moshier

 

[walleyehed]

Re: Prop questions

From the blade leading edge, go BACK behind the contact point of blade to the hub, 5/8" and make a verticle mark, or parallel mark to the center-line of hub.
Then, measure 5/8' to 11/16" "UP" from the fwd most rim of outer hub and mark a line "though" the verticle line.
The center of those 2 lines is the point you want to tap with a center punch as a drill-guide.
After Marking those points, look inside the hub and make sure those points will not cause you to drill through any of the webbing that is molded to the inner-outer hub-holding it together. If needed, you can move the verticle line back farther...3/4" to 1" if needed to keep out of the webs in the center when you drill it.
I would start with a small hole of 5/32" and test, and if possible, drill in 1/32" increments until you get the desired result. You CAN go too big, so be careful. I think you could go to 3/8" with no problems, but not all react the same. On an I/O, you "may" be able to get by with bigger holes, but I would still recommend starting small so you can tell the difference it makes.