Posted by jwmcd on 09/03/19 - 11:53 AM
#1
I just put a new Yamaha 4s 70 on my old Montauk. The boat is a 1981 with two batteries in the console and tanks under the RPS. No top . The boat has slick bottom, not water logged , 500 lb total load.The prop furnished is a Solas 3411-138-13. 13.75 D X 13 P . Motor is mounted high, 3 holes up. After break in run, the top RPM is 4200. Speed 31-32 mph. Advice to get RPM up to 6000+ with a stainless prop will be appreciated.
Thanks,
John
Posted by Phil T on 09/03/19 - 12:50 PM
#2
John -
The recommended rigging of a F70 on a 16'7 or 17' hull (Montauk, Newport etc) is:
Engine mounted at least 2 holes up. This means there are 2 empty holes
above the top set of bolts. The bottom bolts are in the ~ middle of the slots.
As for props: For your model, F70 owners have evaluated many props and reported the best results with the ones listed below.
Note that make/model and size is important. Size is not universal across models let alone makes. WOT on the F70 is 6,300 rpm, not 6000.
13 x 17 Yamaha Painted SS
13.25 x 14 Yamaha Performance Series
13.25 x 14 PowerTech SCP (3 holes up)
With a light load, running solo you are trying to reach a WOT rpm of ~6100 and 35mph.