Help again please. Father Frank & Bigshrimpin

[gofastsandman]

`89 20 sf w a 96 ocean pro 150 w/ a mich. 14 1/5 x 17 prop.
Well it now pulls 5500 w 3 ppl and 50 gals at 39 mph on a 2 way pass gps after 100 hrs of new use in the last 4 mos.
Here`s the confusion/ ignorance.

Merc`s online prop selector for a mirage plus for light load
is 15.250 x 19 ,a good load is 15.380 x 18.

Does the difference in design allow for more diameter and pitch?

I have only about 3/4" - 1" of clearance to the vent plate.
Is that also a concern?

Thanks to all
GFS

[Fr. Frank]

... Does the difference in design allow for more diameter and pitch?
I have only about 3/4" - 1" of clearance to the vent plate.
Is that also a concern?

Question 1. Yes, sometimes, depending on rake, progression, amount and type of blade cupping, etcetera.

Question 2. No, that's not a concern. A SS prop will only flex about .0008 to .0010 of an inch under load. Aluminum flex is generally about .04 to .06 of an inch. The biggest concern may be your torque tab under the cavitation plate, behind the prop.

[gofastsandman]

Thanks Father,

Little Jimmy said he usually gets a Baby Ruth bar after confessional....

Would you go with an 18 of maybe a 17. I`m afraid of over- propping.

Thx,
GFS
Sorry to see you`re selling the baby, if you find yourself in W.P.B. drop me a line and we can go drop a line.

[Fr. Frank]

I'd go with the lower pitch. You will lose some top end, but gain acceleration and maneuverability, and place less strain on the engine when under heavy load, and it will run easy under moderate or light loads. You should be capable of turning maximum rpms with a maximum gross weight load.
For instance, my Merc has a reccomended max rpm range of 5400 to 5800 rpms. I can turn 5800 with 7 people and full fuel, and 6150 lightly loaded.

[gofastsandman]

Thanks sooooo much for your professional advice and courtesy.

Are you getting another boat?

GFS

[Fr. Frank]

Yes, and no. I have received so much support and encouragement, my wife says she won't mind if the Seafari doesn't sell. We still have the 17' Carolina Skiff and the 14' Caribe glass-bottom kayak, anyway.