help me with my prop stats.

[cdoliver]

I've tried some different props and I'm hoping someone can help me with the results:
1979 johnny 115 on a 1980 skeeter wrangler (semi V) approx 1200lbs
I have tried two props. Both from the same era as the motor, both SS and in good shape. Motor is recently rebuilt and running great. Cav. Plate is 1" above the bottom of the boat
1st one:

13 3/8 X 17
44.2 mph (GPS) @ 6200 with trim

and

13 X19 X 19
46.5 mph (GPS) @ 5600 with trim

pic of motor height:

I'd like to get to somewhere between that. Is there a modern day prop that you would reccomend to get me where I need to be. is a 600 rpm drop correct? Thank you for your help as always.

 

[cdoliver]

Re: help me with my prop stats.

pic might be better this way

http://imgfreehost.com/out.php?i19126_IMG00097.jpg

 

[steelespike]

Re: help me with my prop stats.

I'm not a pro but to me the 19 is right on and a 600 rpm drop is in the ball park.19 could be a better design perhaps more cup.If your not having any ventilation problems I would try another hole higher.Could get you some more rpm and speed.I also would consider something like smart tabs instead of the foil.I'm sure someone will be along with more expertise.

 

[cdoliver]

Re: help me with my prop stats.

Thanks. Should I get one of these props cupped or buy another prop that is already cupped? If I buy a cupped prop, should I start with a 17 or 19? Also, should I look at other diameters? Lastly, what would be a good brand/ type of prop to start with?

 

[codertimt]

Re: help me with my prop stats.

Just a question. Should you be looking for more RPM? Isn't the max rpm for that motor listed at 5500? For all I know, it might be common knowledge that this vintage of v4 likes to rev higher than the listed max rpm...

Just thought I'd throw that out there...

***************EDIT*****************
Okay, I just read one of Wally's posts in another thread stating that with the fuel/oil of today, 300-400 rpm over th listed max is probably good for these older motors. So...nothing to see here...sorry for the interruption...

 

[cdoliver]

Re: help me with my prop stats.

Ok, the wind died down and I got back on the water today. I raised the motor 1.25 inch (2 holes up) and took the hydrofoil off. I don't see any improvement. I'm looking at 45.6mph (gps) @ 5500 with the 19p. I could make it cavitate and could not make it porpus with the trim. the hole shot is very , very slow. Is there anything between the 17p and the 19p? Maybe a 17p with a lot of cup??? I don't know what else to try. Thanks for the help.