Posted by robertleary on 08/24/22 - 9:03 AM
#1
It seems like this should have been discussed and answered already, but I can't find it here. I have a 1984 15 Super Sport with a 1994 Mercury 3 cylinder 60HP ELPTO. Currently has an aluminum 10X17 quicksilver prop. I don't have a tach, but top speed with GPS I've seen with only me and a little bit of gear in the boat is about 37mph. When the boat is loaded with 2 adults and 2 kids (450LBs of people) it's a little sluggish getting on a plane and top speed is around 30mph. I've seen discussions about a 70hp yamaha that generally suggest a 13X17 or 13/19, but I see the ratio for Yamahas seems to be very different than that of Mercs so not sure if that suggestion applies.
My goal would be to get out of the hole fast with reasonable top end.
I was thinking maybe I should get a tach first, but then started looking into the accuracy of tachs and it seems they can be pretty inaccurate anyway. I wanted a tach with a white background and an hour meter.
Any suggestions or experience with props for these Mercs?
Posted by Phil T on 08/25/22 - 8:59 AM
#2
You need a tach.
The diameter is too small and the pitch too much for that gear ratio.
Your engine has a gear ratio of 1.64 and a WOT rpm of 5500. With a target speed of 40, you will need a 13" pitch prop.
Now given that all props have different blade design and sizing is not universal, the specific models of prop to choose are important.
Whaler owners running a Mercury 60hp, 2-stroke recommend Stilleto and Vengeance models. I would start there, after you get a tach.
Also - The engine should be mounted 2 holes up. Top bolt in the 3rd bracket hole down from the top.